Chinnapat Panwisawas | Queen Mary, University of London (original) (raw)

Papers by Chinnapat Panwisawas

Multi-Scale Modeling for Multi-Track Multi-Layer Laser Powder Bed Fusion Additive Manufacturing: A Material Dependent Meltpools, Micro-Void Defects and Mechanics Study

SSRN Electronic Journal

International Journal of Minerals, Metallurgy and Materials

Data-driven algorithms for predicting mechanical properties with small datasets are evaluated in ... more Data-driven algorithms for predicting mechanical properties with small datasets are evaluated in a case study on gear steel hardenability. The limitations of current data-driven algorithms and empirical models are identified. Challenges in analysing small datasets are discussed, and solution is proposed to handle small datasets with multiple variables. Gaussian methods in combination with novel predictive algorithms are utilized to overcome the challenges in analysing gear steel hardenability data and to gain insight into alloying elements interaction and structure homogeneity. The gained fundamental knowledge integrated with machine learning is shown to be superior to the empirical equations in predicting hardenability. Metallurgical-property relationships between chemistry, sample size, and hardness are predicted via two optimized machine learning algorithms: neural networks (NNs) and extreme gradient boosting (XGboost). A comparison is drawn between all algorithms, evaluating the...

Insight into the sensitivities of freckles in the directional solidification of single-crystal turbine blades

Journal of Manufacturing Processes, 2022

A New Toxic-Free Ti40zr10co36pd14 Metallic Glass with Good Biocompatibility and Surface Behavior Comparable to Ti-6al-4v

SSRN Electronic Journal, 2022

Materials Science and Engineering: A, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Acta Materialia, 2020

Primary spacing is a key phenomenon during solidification of single crystal alloys. It determines... more Primary spacing is a key phenomenon during solidification of single crystal alloys. It determines microsegregation, defect formation, the time required to solutionise the solidified structure, and the final performance of single crystal components. A novel stereological characterisation algorithm: Shape-Limited Primary Spacing (SLPS) is developed and applied to study the formation of cellular and dendritic packing patterns in single crystal alloys solidified under different casting conditions. The results reveal the tendency for single crystals to form hexagonally packed structures under steady state conditions, while all other packing arrangements constitute a metastable state. Using the SLPS algorithm, it has been demonstrated that packing pattern formation and local primary spacing can be related to tip growth kinetics. Further, the role of curved isotherms that occur in directional solidification has been identified. Isotherm curvature results in non-uniform liquid compositional gradients developing parallel to a growing solid interface, leading to the formation of metastable packing, low-angle grain boundaries, and porosity formation within the microstructure.

Materials Letters, 2018

Selective-laser melting (SLM) is one of the most rapidly developing and promising of all the so-c... more Selective-laser melting (SLM) is one of the most rapidly developing and promising of all the so-called "Additive Manufacture" routes due to its capability to produce component geometries that would prove impossible using traditional manufacture. A selective-laser melting fabricated cuboid component was built using powder CM247LC, using standard methods, and this was subsequently analysed using neutron tomography methodology to allow for three-dimensional visualisation of the exterior and the interior of the component. The resulting neutron radiographs were processed and analysed for evidence of both porosity and grain boundary segregation within the component.

Metallurgical and Materials Transactions A, 2018

Acta Materialia, 2018

A multi-phase, multi-component mean-field model has been developed for simulating the intermetall... more A multi-phase, multi-component mean-field model has been developed for simulating the intermetallic precipitation kinetics in Inconel 718. The aim of this work is to develop predictive capability to aid in process optimisation and explore precipitation kinetics during additive manufacturing (AM). The model has been calibrated to available experimental data, and then applied to predict precipitation kinetics during typical solid solution treatment and aging operations, and during AM. It is shown that a Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD) based modelling approach provides a unified particle growth rate which can capture the growth, coarsening and dissolution of γ ′ , γ * and δ precipitates under relevant heat treatment conditions. To apply the model to AM, finite element simulations of a simple rectangular build have been carried out, using a property switching method to simulate the material deposition. The component level simulation provides the thermal fields to calculate precipitation kinetics during deposition, also allowing for the examination of the heat affected zone in the substrate. The modelling approach can capture the repeated nucleation and dissolution of precipitates that occurs during AM. The model shows good agreement with experimental data when applied to predicting precipitation kinetics during heat treatment.

Materials & Design, 2018

Grain boundary migration in the presence of concentrated sources of heat is a complex process tha... more Grain boundary migration in the presence of concentrated sources of heat is a complex process that has a considerable impact on resultant material properties. A phase eld model is presented incorporating thermal gradient and curvature driving force terms to predict how a poly-crystalline network evolves due to the application of such heat sources, as grain boundaries migrate due to local boundary curvature and time varying thermal gradients. Various thermal scenarios are investigated, in both two and three dimensions. These scenarios include both partial and full penetration laser induced melting, the application of a linearly varying time-independent thermal eld, and successive melting events where regions experience multiple melting and solidication cycles. Comparisons are made between the microstructures predicted by the proposed phase eld method, during the various thermal scenarios, that agree with commonly observed phenomena. Particularly interesting is the ability to explain the dierences in grain morphology between the full penetration and partial penetration welds using the phase eld model and associated driving force magnitudes between the two scenarios. The model predicts the restoration of grain boundary networks in regions experiencing multiple melting events, and explains the differences in grain morphology due to the local curvature and thermal gradient eects.

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2018

This paper presents a computational framework to study the differences in process-induced microvo... more This paper presents a computational framework to study the differences in process-induced microvoid and precipitate distributions during selective laser melting (SLM) of two nickel-based superalloys representative of low (IN718) and high (CM247LC) volume fraction precipitate-strengthened alloys. Simulations indicate that CM247LC has a higher propensity to form process-induced microvoids than IN718. Particle sintering is predicted to be strongly influenced by the powder size distribution. For deposition thickness of approximately 40 μm, thermal gradients during cooling are predicted to be larger for CM247LC than IN718 and consequently expect the development of larger residual stresses for a high volume fractionγ′ alloy. A coupled mean field/finite-element approach has been used to predict the precipitate distributions across a simple rectangular build and during a subsequent hot isostatic pressing (HIP) cycle. Unimodal and multi-modal particle distributions are predicted for IN718 an...

Journal of Materials Processing Technology, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Acta Materialia, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Scripta Materialia, 2017

The stress relaxation behaviour of a single crystal nickel-base superalloy has been quantified us... more The stress relaxation behaviour of a single crystal nickel-base superalloy has been quantified using time-offlight neutron diffraction analysis for a range of temperatures relevant to casting. A new iterative analysis methodology is described to isolate the lattice strain behaviour of the c matrix and c precipitate phases from data obtained sufficiently rapidly to help elucidate the microscopic effect of macroscopic stress relaxation. The independent response of c and c is revealed, showing the temperature sensitivity of lattice strain relaxation. The c/c response is discussed in the context of thermo-mechanical conditions that may affect the propensity for recrystallisation.

A Multi-Scale Multi-Physics Approach to Modelling of Additive Manufacturing in Nickel-Based Superalloys

Superalloys 2016, 2016

A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-b... more A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-based superalloy IN718 is presented. Representative powder-bed particle distribution is simulated usi ...

Acta Materialia, 2017

High energy-density beam welding, such as electron beam or laser welding, has found a number of i... more High energy-density beam welding, such as electron beam or laser welding, has found a number of industrial applications for clean, high-integrity welds. The deeply penetrating nature of the joints is enabled by the formation of metal vapour which creates a narrow fusion zone known as a "keyhole". However the formation of the keyhole and the associated keyhole dynamics, when using a moving laser heat source, requires further research as they are not fully understood. Porosity, which is one of a number of process induced phenomena related to the thermal fluid dynamics, can form during beam welding processes. The presence of porosity within a welded structure, inherited from the fusion welding operation, degrades the mechanical properties of components during service such as fatigue life. In this study, a physics-based model for keyhole welding including heat transfer, fluid flow and interfacial interactions has been used to simulate keyhole and porosity formation during laser welding of Ti-6Al-4V titanium alloy. The modelling suggests that keyhole formation and the time taken to achieve keyhole penetration can be predicted, and it is important to consider the thermal fluid flow at the melting front as this dictates the evolution of the fusion zone. Processing 2 induced porosity is significant when the fusion zone is only partially penetrating through the thickness of the material. The modelling results are compared with high speed camera imaging and measurements of porosity from welded samples using X-ray computed tomography, radiography and optical micrographs. These are used to provide a better understanding of the relationship between process parameters, component microstructure and weld integrity.

Materials & Design, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Porosity Formation in Laser Welded Ti-6Al-4V Alloy: Modelling and Validation

TMS/Proceedings, 2016

The presence of porosity inherited from a fusion welding operation degrades the mechanical proper... more The presence of porosity inherited from a fusion welding operation degrades the mechanical properties of components during performance such as fatigue life. In this study, a physics-based model including heat transfer, fluid flow, interfacial processes and microstructure prediction via cellular automata has been developed and used to simulate porosity formation during laser welding of Ti-6Al-4V titanium alloy. The model results are compared with: measurements of porosity from welded samples using X-ray tomography; optical images; texture measurement via EBSD and neutron diffraction. These are used to provide a better understanding of the relationship between process parameters, component microstructure and weld integrity.

Metallurgical and Materials Transactions B, 2015

This document is the author's post-print version, incorporating any revisions agreed during the p... more This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Materials Science and Technology, 2013

To provide insight into the factors causing recrystallisation of nickel-based single crystal supe... more To provide insight into the factors causing recrystallisation of nickel-based single crystal superalloys, analysis of the thermal-mechanical deformation caused by investment casting of these components is presented. Three-dimensional thermal-mechanical finite element analysis is first used to demonstrate that the reaction of the casting and mould-at least in the aerofoil section-can be approximated as one-dimensional. One-dimensional models are then built based upon static equilibrium for plasticity on the microscale caused by differential thermal contraction of metal, mould and core, using temperature dependent material properties. The models take various forms to study the mechanical response under different situations relevant to practical applications. The results indicate that the plastic strain causing recrystallisation is likely to be induced during cooling at temperatures above 1000uC. The relative importance of thicker and stiffer ceramic shells is studied. Our analysis indicates that it is important to account for creep deformation for such applications.

Multi-Scale Modeling for Multi-Track Multi-Layer Laser Powder Bed Fusion Additive Manufacturing: A Material Dependent Meltpools, Micro-Void Defects and Mechanics Study

SSRN Electronic Journal

International Journal of Minerals, Metallurgy and Materials

Data-driven algorithms for predicting mechanical properties with small datasets are evaluated in ... more Data-driven algorithms for predicting mechanical properties with small datasets are evaluated in a case study on gear steel hardenability. The limitations of current data-driven algorithms and empirical models are identified. Challenges in analysing small datasets are discussed, and solution is proposed to handle small datasets with multiple variables. Gaussian methods in combination with novel predictive algorithms are utilized to overcome the challenges in analysing gear steel hardenability data and to gain insight into alloying elements interaction and structure homogeneity. The gained fundamental knowledge integrated with machine learning is shown to be superior to the empirical equations in predicting hardenability. Metallurgical-property relationships between chemistry, sample size, and hardness are predicted via two optimized machine learning algorithms: neural networks (NNs) and extreme gradient boosting (XGboost). A comparison is drawn between all algorithms, evaluating the...

Insight into the sensitivities of freckles in the directional solidification of single-crystal turbine blades

Journal of Manufacturing Processes, 2022

A New Toxic-Free Ti40zr10co36pd14 Metallic Glass with Good Biocompatibility and Surface Behavior Comparable to Ti-6al-4v

SSRN Electronic Journal, 2022

Materials Science and Engineering: A, 2021

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Acta Materialia, 2020

Primary spacing is a key phenomenon during solidification of single crystal alloys. It determines... more Primary spacing is a key phenomenon during solidification of single crystal alloys. It determines microsegregation, defect formation, the time required to solutionise the solidified structure, and the final performance of single crystal components. A novel stereological characterisation algorithm: Shape-Limited Primary Spacing (SLPS) is developed and applied to study the formation of cellular and dendritic packing patterns in single crystal alloys solidified under different casting conditions. The results reveal the tendency for single crystals to form hexagonally packed structures under steady state conditions, while all other packing arrangements constitute a metastable state. Using the SLPS algorithm, it has been demonstrated that packing pattern formation and local primary spacing can be related to tip growth kinetics. Further, the role of curved isotherms that occur in directional solidification has been identified. Isotherm curvature results in non-uniform liquid compositional gradients developing parallel to a growing solid interface, leading to the formation of metastable packing, low-angle grain boundaries, and porosity formation within the microstructure.

Materials Letters, 2018

Selective-laser melting (SLM) is one of the most rapidly developing and promising of all the so-c... more Selective-laser melting (SLM) is one of the most rapidly developing and promising of all the so-called "Additive Manufacture" routes due to its capability to produce component geometries that would prove impossible using traditional manufacture. A selective-laser melting fabricated cuboid component was built using powder CM247LC, using standard methods, and this was subsequently analysed using neutron tomography methodology to allow for three-dimensional visualisation of the exterior and the interior of the component. The resulting neutron radiographs were processed and analysed for evidence of both porosity and grain boundary segregation within the component.

Metallurgical and Materials Transactions A, 2018

Acta Materialia, 2018

A multi-phase, multi-component mean-field model has been developed for simulating the intermetall... more A multi-phase, multi-component mean-field model has been developed for simulating the intermetallic precipitation kinetics in Inconel 718. The aim of this work is to develop predictive capability to aid in process optimisation and explore precipitation kinetics during additive manufacturing (AM). The model has been calibrated to available experimental data, and then applied to predict precipitation kinetics during typical solid solution treatment and aging operations, and during AM. It is shown that a Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD) based modelling approach provides a unified particle growth rate which can capture the growth, coarsening and dissolution of γ ′ , γ * and δ precipitates under relevant heat treatment conditions. To apply the model to AM, finite element simulations of a simple rectangular build have been carried out, using a property switching method to simulate the material deposition. The component level simulation provides the thermal fields to calculate precipitation kinetics during deposition, also allowing for the examination of the heat affected zone in the substrate. The modelling approach can capture the repeated nucleation and dissolution of precipitates that occurs during AM. The model shows good agreement with experimental data when applied to predicting precipitation kinetics during heat treatment.

Materials & Design, 2018

Grain boundary migration in the presence of concentrated sources of heat is a complex process tha... more Grain boundary migration in the presence of concentrated sources of heat is a complex process that has a considerable impact on resultant material properties. A phase eld model is presented incorporating thermal gradient and curvature driving force terms to predict how a poly-crystalline network evolves due to the application of such heat sources, as grain boundaries migrate due to local boundary curvature and time varying thermal gradients. Various thermal scenarios are investigated, in both two and three dimensions. These scenarios include both partial and full penetration laser induced melting, the application of a linearly varying time-independent thermal eld, and successive melting events where regions experience multiple melting and solidication cycles. Comparisons are made between the microstructures predicted by the proposed phase eld method, during the various thermal scenarios, that agree with commonly observed phenomena. Particularly interesting is the ability to explain the dierences in grain morphology between the full penetration and partial penetration welds using the phase eld model and associated driving force magnitudes between the two scenarios. The model predicts the restoration of grain boundary networks in regions experiencing multiple melting events, and explains the differences in grain morphology due to the local curvature and thermal gradient eects.

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2018

This paper presents a computational framework to study the differences in process-induced microvo... more This paper presents a computational framework to study the differences in process-induced microvoid and precipitate distributions during selective laser melting (SLM) of two nickel-based superalloys representative of low (IN718) and high (CM247LC) volume fraction precipitate-strengthened alloys. Simulations indicate that CM247LC has a higher propensity to form process-induced microvoids than IN718. Particle sintering is predicted to be strongly influenced by the powder size distribution. For deposition thickness of approximately 40 μm, thermal gradients during cooling are predicted to be larger for CM247LC than IN718 and consequently expect the development of larger residual stresses for a high volume fractionγ′ alloy. A coupled mean field/finite-element approach has been used to predict the precipitate distributions across a simple rectangular build and during a subsequent hot isostatic pressing (HIP) cycle. Unimodal and multi-modal particle distributions are predicted for IN718 an...

Journal of Materials Processing Technology, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Acta Materialia, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Scripta Materialia, 2017

The stress relaxation behaviour of a single crystal nickel-base superalloy has been quantified us... more The stress relaxation behaviour of a single crystal nickel-base superalloy has been quantified using time-offlight neutron diffraction analysis for a range of temperatures relevant to casting. A new iterative analysis methodology is described to isolate the lattice strain behaviour of the c matrix and c precipitate phases from data obtained sufficiently rapidly to help elucidate the microscopic effect of macroscopic stress relaxation. The independent response of c and c is revealed, showing the temperature sensitivity of lattice strain relaxation. The c/c response is discussed in the context of thermo-mechanical conditions that may affect the propensity for recrystallisation.

A Multi-Scale Multi-Physics Approach to Modelling of Additive Manufacturing in Nickel-Based Superalloys

Superalloys 2016, 2016

A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-b... more A multi-scale, multi-physics modelling framework of selective laser melting (SLM) in the nickel-based superalloy IN718 is presented. Representative powder-bed particle distribution is simulated usi ...

Acta Materialia, 2017

High energy-density beam welding, such as electron beam or laser welding, has found a number of i... more High energy-density beam welding, such as electron beam or laser welding, has found a number of industrial applications for clean, high-integrity welds. The deeply penetrating nature of the joints is enabled by the formation of metal vapour which creates a narrow fusion zone known as a "keyhole". However the formation of the keyhole and the associated keyhole dynamics, when using a moving laser heat source, requires further research as they are not fully understood. Porosity, which is one of a number of process induced phenomena related to the thermal fluid dynamics, can form during beam welding processes. The presence of porosity within a welded structure, inherited from the fusion welding operation, degrades the mechanical properties of components during service such as fatigue life. In this study, a physics-based model for keyhole welding including heat transfer, fluid flow and interfacial interactions has been used to simulate keyhole and porosity formation during laser welding of Ti-6Al-4V titanium alloy. The modelling suggests that keyhole formation and the time taken to achieve keyhole penetration can be predicted, and it is important to consider the thermal fluid flow at the melting front as this dictates the evolution of the fusion zone. Processing 2 induced porosity is significant when the fusion zone is only partially penetrating through the thickness of the material. The modelling results are compared with high speed camera imaging and measurements of porosity from welded samples using X-ray computed tomography, radiography and optical micrographs. These are used to provide a better understanding of the relationship between process parameters, component microstructure and weld integrity.

Materials & Design, 2017

Where a licence is displayed above, please note the terms and conditions of the licence govern yo... more Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

Porosity Formation in Laser Welded Ti-6Al-4V Alloy: Modelling and Validation

TMS/Proceedings, 2016

The presence of porosity inherited from a fusion welding operation degrades the mechanical proper... more The presence of porosity inherited from a fusion welding operation degrades the mechanical properties of components during performance such as fatigue life. In this study, a physics-based model including heat transfer, fluid flow, interfacial processes and microstructure prediction via cellular automata has been developed and used to simulate porosity formation during laser welding of Ti-6Al-4V titanium alloy. The model results are compared with: measurements of porosity from welded samples using X-ray tomography; optical images; texture measurement via EBSD and neutron diffraction. These are used to provide a better understanding of the relationship between process parameters, component microstructure and weld integrity.

Metallurgical and Materials Transactions B, 2015

This document is the author's post-print version, incorporating any revisions agreed during the p... more This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Materials Science and Technology, 2013

To provide insight into the factors causing recrystallisation of nickel-based single crystal supe... more To provide insight into the factors causing recrystallisation of nickel-based single crystal superalloys, analysis of the thermal-mechanical deformation caused by investment casting of these components is presented. Three-dimensional thermal-mechanical finite element analysis is first used to demonstrate that the reaction of the casting and mould-at least in the aerofoil section-can be approximated as one-dimensional. One-dimensional models are then built based upon static equilibrium for plasticity on the microscale caused by differential thermal contraction of metal, mould and core, using temperature dependent material properties. The models take various forms to study the mechanical response under different situations relevant to practical applications. The results indicate that the plastic strain causing recrystallisation is likely to be induced during cooling at temperatures above 1000uC. The relative importance of thicker and stiffer ceramic shells is studied. Our analysis indicates that it is important to account for creep deformation for such applications.

Multi-scale, Multi-physics Approach to Modelling of Fusion Welding in Titanium Alloys

Multi-scale, Multi-physics Approach to Modelling of Fusion Welding

On the Role of Creep Deformation during Investment Casting of a Single Crystal Superalloy

Prediction of Plastic Strain for Recrystallisation during Investment Casting of Single Crystal Superalloys

Castings for single crystal aerofoils can be prone to recrystallisation during solution heat trea... more Castings for single crystal aerofoils can be prone to recrystallisation during solution heat treatment; however quantitative information concerning the factors causing this phenomenon is lacking. In this paper, mathematical modelling and targeted experimentation are used to deduce the levels of localised plastic strain needed for
recrystallisation to occur. The influences of differential thermal contraction against the shell, specimen geometry and stress concentration factor are quantified. The model predicts that the induced strain in the metal increased with the ceramic shell thickness, and in some geometries, with the solidification height. Negligible plastic strains were predicted in a solid casting with no stress concentration features. However, as the geometry became more complex by reducing the casting cross-section, by the insertion of a core and introduction of stress concentration features, the induced plastic strains increased signfi?cantly. The predicted plastic strain for recrystallisation in a cored casting was in good agreement with experimental critical strain data. The model provides the foundation for a systems-based approach which enables recrystallisation to be predicted and thus avoided, prior to its occurrence in the foundry.

Recrystallisation during Investment Casting of a Single Crystal Superalloy

During the manufacturing of investment casting of turbine blades from single crystal superalloys,... more During the manufacturing of investment casting of turbine blades from single crystal superalloys, recrystallisation can potentially occur during subsequent heat treatment. If it is the case, introduction of grain boundary can degrade the fatigue and creep life of the components. Therefore scrappage rate might be increased. In this work, thermo-mechanical modelling along with experimental validation is presented to predict the plastic strain level which proceeds the driving force of recrystallisation. The model indicated that the induced strain in the metal increases with the shell thickness, and in some geometries, with the solidifi cation height. Negligible plastic strains were predicted in a solid casting with no stress concentration features. However, as the geometry became more complex by reducing the casting cross-section, by the insertion of a core and introduction of stress concentration features, the induced plastic strains increased signifi cantly. According to the modelling a maximum plastic strain of 2.5 per cent was induced during casting of a cored analogue casting (1.5 mm wall thickness) that recrystallised after solution heat treatment. Experimental work is critically compared
with modelling.

Analysis of Thermo-Mechanical Effects during Investment Casting of Single Crystal Superalloys

During investment casting, thermo-mechanical effects are important for several reasons. First, on... more During investment casting, thermo-mechanical effects are important for several reasons. First, one needs very precise dimensional control to ensure accurate geometry of the parts; differential thermal contraction of metal, shell and core controls the limits which can be achieved. Second, recrystallisation depends upon localised plasticity which can occur during cooling. In this paper, analysis of the pertinent effects controlling these phenomena is presented. We concentrate upon an Bobbin Test Piece Model with a number of shroud and root features. Finite element modelling is used. Validatory studies using CMSX-4 are carried out using a pilot-scale investment casting facility. Our calculations confirm that localised plasticity does indeed occur but that stress concentration features are required if the strains are to be sufficient for recrystallisation to occur. Deductions are made concerning the temperature regime in which the plasticity needed for recrystallisation occurs.

Numerical Modelling of Recrystallisation in Single Crystal Superalloys