Shoujin Sun - Academia.edu (original) (raw)

Papers by Shoujin Sun

Research paper thumbnail of Metal Alloys for Fusion‐Based Additive Manufacturing

Advanced Engineering Materials, 2018

Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts in... more Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts incrementally layer by layer. Thus, metal AM has inherent advantages in part complexity, time, and waste saving. However, due to its complex thermal cycle and rapid solidification during processing, the alloys well suit and commercially used for metal AM today are limited. Therefore, it is important to understand the alloying strategy and current progress with materials performance to consider alloy development for metal AM. This review presents the current range of alloys available for metal AM, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys, and low melting point alloys), and compositionally complex alloys (including bulk metallic glasses and high entropy alloys) with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system. In addition, some promising alloy systems for metal AM are highlighted. Approaches for designing and optimizing new materials for metal AM have been summarized.

Research paper thumbnail of The Microstructure and Mechanical Properties of As-rolled Dual Phase Steel: Part II - Mechanical Properties

The influence of pre-annealing and post-annealing heat treatments on the tensile properties of du... more The influence of pre-annealing and post-annealing heat treatments on the tensile properties of dual phase steel has been investigated. Post-annealing lowers the tensile strength and increases the % elongation by decreasing the aspect ratio of the fibrous martensite. The asrolled steel shows a 'delamination-type' fracture whereas the post-annealed steel does not. The tensile strength of these partitioned and fibrous steels are compared with Mileiko's theory for plastic instability in ductile composites.

Research paper thumbnail of Powder Bed Fusion Processes

Additive Manufacturing Technologies, 2015

Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at ... more Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at the University of Texas at Austin, USA, Selective Laser Sintering (SLS) was the first commercialized powder bed fusion process. Its basic method of operation is schematically shown in Fig. 5.1, and all other PBF processes modify this basic approach in one or more ways to enhance machine productivity, enable different materials to be processed, and/or to avoid specific patented features.

Research paper thumbnail of Machinability Analysis of Finish-Turning Operations for Ti6Al4V Tubes Fabricated by Selective Laser Melting

Metals

With the advent of additive manufacturing as an advanced technology for the fabrication of titani... more With the advent of additive manufacturing as an advanced technology for the fabrication of titanium components, there is a pressing need to investigate the machinability of parts produced using these techniques compared to components made with conventional wrought methodologies. The motivation for this study was to investigate the influences of machining parameters, especially cutting depth, on the machinability of selective laser melted (SLMed) Ti6Al4V tubes, by analyzing the cutting responses, including cutting forces, machined surface roughness and tool wear at varying cutting parameters. Generally, it can be inferred that specific cutting tools used to machine wrought titanium components can also be used for SLMed parts when carrying out finish-machining operations. Cutting forces in the machining of SLMed workpieces could be up to 70% higher than those in machining the wrought counterparts. In contrast, the tool-wear analysis correspondingly showed larger tool-workpiece engagem...

Research paper thumbnail of Mechanical properties and deformation mechanisms of martensitic Ti6Al4V alloy processed by laser powder bed fusion and water quenching

Materials Science and Engineering: A, 2022

Research paper thumbnail of Laser beam shaping and surface treatment of Ze41A-T5 magnesium alloy

Research paper thumbnail of Laser assisted machining of commercially pure titanium

International Congress on Applications of Lasers & Electro-Optics, 2007

Research paper thumbnail of Exploring Macroporosity of Additively Manufactured Titanium Metamaterials for Bone Regeneration with Quality by Design: A Systematic Literature Review

Materials, 2020

Additive manufacturing facilitates the design of porous metal implants with detailed internal arc... more Additive manufacturing facilitates the design of porous metal implants with detailed internal architecture. A rationally designed porous structure can provide to biocompatible titanium alloys biomimetic mechanical and biological properties for bone regeneration. However, increased porosity results in decreased material strength. The porosity and pore sizes that are ideal for porous implants are still controversial in the literature, complicating the justification of a design decision. Recently, metallic porous biomaterials have been proposed for load-bearing applications beyond surface coatings. This recent science lacks standards, but the Quality by Design (QbD) system can assist the design process in a systematic way. This study used the QbD system to explore the Quality Target Product Profile and Ideal Quality Attributes of additively manufactured titanium porous scaffolds for bone regeneration with a biomimetic approach. For this purpose, a total of 807 experimental results extr...

Research paper thumbnail of Challenges in laser-assisted milling of titanium alloys

International Journal of Extreme Manufacturing, 2021

Several detailed studies have comprehensively investigated the benefits and limitations of laser-... more Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining (LAM) of titanium alloys. These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life. This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process. The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.

Research paper thumbnail of Tool wear mechanisms involved in crater formation on uncoated carbide tool when machining Ti6Al4V alloy

The International Journal of Advanced Manufacturing Technology, 2015

When machining titanium alloys at cutting speeds higher than 60 m/min using cemented carbide cutt... more When machining titanium alloys at cutting speeds higher than 60 m/min using cemented carbide cutting tools, the tool wears out rapidly. With the ever-increasing use of titanium alloys, it is essential to address this issue of rapid tool wear in order to reduce manufacturing costs. Therefore, the intention of this study was to investigate all possible tool wear mechanisms involved when using uncoated carbide cutting tools to machine Ti6Al4V titanium alloy at a cutting speed of 150 m/min under dry cutting conditions. Adhesion, diffusion, attrition, and abrasion were found to be the mechanisms associated with the cratering of the rake surface of the cutting tool. The plastic deformation of the cutting edge was also noticed which resulted in weakening of the rake surface and clear evidence has been presented. Based on this evidence, the process of the formation of the crater wear has been described in detail.

Research paper thumbnail of Microstructure and hardness characterisation of laser coatings produced with a mixture of AISI 420 stainless steel and Fe-C-Cr-Nb-B-Mo steel alloy powders

Surface and Coatings Technology, 2016

Fe-C-Cr-Nb-B-Mo alloy powder and AISI 420 SS powder are deposited using laser cladding to increas... more Fe-C-Cr-Nb-B-Mo alloy powder and AISI 420 SS powder are deposited using laser cladding to increase the hardness for wear resistant applications. Mixtures from 0 to 100 wt.% were evaluated to understand the effect on the elemental composition, microstructure, phases, and microhardness. The mixture of carbon, boron and niobium in the Fe-C-Cr-Nb-B-Mo alloy powder introduces complex carbides into a Fe-based matrix of AISI 420 SS which increases its hardness. Hardness increased linearly with increasing Fe-C-Cr-Nb-B-Mo alloy, but substantial micro-cracking was observed in the clad layer at additions of 60 wt.% and above; related to a transition from a hypoeutectic alloy containing α-Fe/α' dendrites with an (Fe,Cr)2B and γ-Fe eutectic to primary and continuous carbo-borides M2B (where M represents Fe and Cr) and M23(B,C)6 carbides (where M represents Fe, Cr, Mo) with MC particles (where M represents Nb and Mo). The highest average hardness, for an alloy without micro-cracking, of 952 HV was observed in a 40 wt.% alloy. High stress abrasive scratch testing was conducted on all alloys at various loads (500, 1500, 2500 N). Alloy content was found to have a strong effect on the wear mode and the abrasive wear rate, and the presence of micro-cracks was detrimental to abrasive wear resistance.

Research paper thumbnail of Numerical and Experimental Investigation of the Heat-Affected Zone in a Laser-Assisted Machining of Ti-6 Al-4 V Alloy Process

The aim of this work is to develop a 3-D transient finite element model for a moving Gaussian las... more The aim of this work is to develop a 3-D transient finite element model for a moving Gaussian laser heat source to predict the depth of the heat-affected zone (HAZ) and temperature distribution in a Ti6Al4V alloy workpiece. It is found that the temperature profile and depth of HAZ are strongly dependent on the parameters of the laser beam. The thermal model simulations are compared with results produced by experimental work and these show close agreement. Introduction Titanium alloys have been widely used in the aerospace, biomedical and automotive industries because of their high strength-to-weight ratio and superior corrosion resistance. However, it is very difficult to machine these alloys due to their poor machinability [1]. Laser assisted machining (LAM) is a new and innovative manufacturing process that has been investigated as an alternative to conventional machining of hard and/or difficult-to-process materials such as titanium alloys [2-7]. This heat-assisted process induce...

Research paper thumbnail of Insights into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

Metals

New metastable β titanium alloys are receiving increasing attention due to their excellent biomec... more New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study, machining chip microstructure has been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400–600 °C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20–50 nm, while further from the interface the β grains become highl...

Research paper thumbnail of Effect of laser beam on the chip formation in machining of titanium alloys

International Congress on Applications of Lasers & Electro-Optics

Research paper thumbnail of Effect of tool wear evolution on chip formation during dry machining of Ti-6Al-4V alloy

International Journal of Machine Tools and Manufacture

Research paper thumbnail of Correlation between melt pool temperature and clad formation in pulsed and continuous wave Nd:YAG laser cladding of stellite 6

Pacific International Conference on Applications of Lasers and Optics

The melt pool temperature in pulsed laser cladding of stellite 6 was measured with a two-colour p... more The melt pool temperature in pulsed laser cladding of stellite 6 was measured with a two-colour pyrometer. The pulse peak temperature (p T), durations when the melt and continuous wave (CW) laser cladding of stellite 6. Comparison between the experimental data and prediction has been made. Thick clad layer with low level of dilution requires higher value of the product of f t 1 ⋅ , longer beam interaction time (τ) and large M D .

Research paper thumbnail of Insights Into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

New metastable β titanium alloys are receiving increasing attention due to their excellent biomec... more New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study machining chip microstructure have been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400-600°C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20-50 nm, while further from the interface the β grains become highly elongated in the shear direction. An absence of the α phase in the region immediately adjacent to the cutting interface indicates recrystallization during cutting and temperatures in excess of the 720°C β transus temperature.

Research paper thumbnail of Experimental investigation of cutting forces and tool wear during laser-assisted milling of Ti-6Al-4V alloy

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigate... more The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigated. The effects of laser processing and milling parameters on cutting forces and tool wear have been examined. It is found that local heating and softening of the workpiece by the laser beam in front of the cutting tool significantly reduced the cutting forces, especially the force in the feed direction during up-cut milling. Laser power, tool-beam distance, depth of cut and cutting speed are the parameters influencing the change of feed force during laser-assisted milling. Analysis of the workpiece temperature rise due to laser beam heating shows that the feed force is strongly dependent on the workpiece temperature in front of the cutting zone; significant reduction of feed force occurred when the temperature in front of the cutting zone was in the range 200-450 C. Edge chipping is found to be the tool failure mode for both conventional milling and laser-assisted milling. A significant improvement in tool life during laser-assisted milling was obtained when the workpiece temperature in front of the cutting zone was at an optimum value. Compressed air was used to remove the chip from the cutting tool, which made the milling process more effective. The optimum workpiece temperature in front of the cutting zone with compressed air delivered through the spindle is about 350 C, higher than that with compressed air delivered through a stationary nozzle (about 230 C). The maximum tool life in the former case is much longer than that in the latter case.

Research paper thumbnail of Effect of tool wear on chip formation during dry machining of Ti-6Al-4V alloy, part 1: Effect of gradual tool wear evolution

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

Geometric features of the segmented chip have been investigated along with the volume of material... more Geometric features of the segmented chip have been investigated along with the volume of material removed at a cutting speed at which tool wear is characterized by the gradual development of flank wear when cutting Ti-6Al-4V alloy. The chip geometric variables varied with an increase in the volume of material removed as the combined effect of change in tool’s geometry and increase in cutting temperature. Plastic deformation dimples were observed as periodical regions on the machined surface, a row on each undeformed surface and region on the top of the slipping surface of the segmented chip when cutting with new tool; these dimples on the undeformed surface and machined surface are elongated in the direction of chip flow. All these dimples became less with an increase in the volume of material removed and almost disappeared when the chip was removed with the worn tool at the end of its life. A model of segmented chip formation process has been proposed to satisfactorily explain the ...

Research paper thumbnail of A case-study on the mechanism of flank wear during laser-assisted machining of a titanium alloy

International Journal of Machining and Machinability of Materials

Research paper thumbnail of Metal Alloys for Fusion‐Based Additive Manufacturing

Advanced Engineering Materials, 2018

Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts in... more Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts incrementally layer by layer. Thus, metal AM has inherent advantages in part complexity, time, and waste saving. However, due to its complex thermal cycle and rapid solidification during processing, the alloys well suit and commercially used for metal AM today are limited. Therefore, it is important to understand the alloying strategy and current progress with materials performance to consider alloy development for metal AM. This review presents the current range of alloys available for metal AM, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys, and low melting point alloys), and compositionally complex alloys (including bulk metallic glasses and high entropy alloys) with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system. In addition, some promising alloy systems for metal AM are highlighted. Approaches for designing and optimizing new materials for metal AM have been summarized.

Research paper thumbnail of The Microstructure and Mechanical Properties of As-rolled Dual Phase Steel: Part II - Mechanical Properties

The influence of pre-annealing and post-annealing heat treatments on the tensile properties of du... more The influence of pre-annealing and post-annealing heat treatments on the tensile properties of dual phase steel has been investigated. Post-annealing lowers the tensile strength and increases the % elongation by decreasing the aspect ratio of the fibrous martensite. The asrolled steel shows a 'delamination-type' fracture whereas the post-annealed steel does not. The tensile strength of these partitioned and fibrous steels are compared with Mileiko's theory for plastic instability in ductile composites.

Research paper thumbnail of Powder Bed Fusion Processes

Additive Manufacturing Technologies, 2015

Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at ... more Powder bed fusion (PBF) processes were among the first commercialized AM processes. Developed at the University of Texas at Austin, USA, Selective Laser Sintering (SLS) was the first commercialized powder bed fusion process. Its basic method of operation is schematically shown in Fig. 5.1, and all other PBF processes modify this basic approach in one or more ways to enhance machine productivity, enable different materials to be processed, and/or to avoid specific patented features.

Research paper thumbnail of Machinability Analysis of Finish-Turning Operations for Ti6Al4V Tubes Fabricated by Selective Laser Melting

Metals

With the advent of additive manufacturing as an advanced technology for the fabrication of titani... more With the advent of additive manufacturing as an advanced technology for the fabrication of titanium components, there is a pressing need to investigate the machinability of parts produced using these techniques compared to components made with conventional wrought methodologies. The motivation for this study was to investigate the influences of machining parameters, especially cutting depth, on the machinability of selective laser melted (SLMed) Ti6Al4V tubes, by analyzing the cutting responses, including cutting forces, machined surface roughness and tool wear at varying cutting parameters. Generally, it can be inferred that specific cutting tools used to machine wrought titanium components can also be used for SLMed parts when carrying out finish-machining operations. Cutting forces in the machining of SLMed workpieces could be up to 70% higher than those in machining the wrought counterparts. In contrast, the tool-wear analysis correspondingly showed larger tool-workpiece engagem...

Research paper thumbnail of Mechanical properties and deformation mechanisms of martensitic Ti6Al4V alloy processed by laser powder bed fusion and water quenching

Materials Science and Engineering: A, 2022

Research paper thumbnail of Laser beam shaping and surface treatment of Ze41A-T5 magnesium alloy

Research paper thumbnail of Laser assisted machining of commercially pure titanium

International Congress on Applications of Lasers & Electro-Optics, 2007

Research paper thumbnail of Exploring Macroporosity of Additively Manufactured Titanium Metamaterials for Bone Regeneration with Quality by Design: A Systematic Literature Review

Materials, 2020

Additive manufacturing facilitates the design of porous metal implants with detailed internal arc... more Additive manufacturing facilitates the design of porous metal implants with detailed internal architecture. A rationally designed porous structure can provide to biocompatible titanium alloys biomimetic mechanical and biological properties for bone regeneration. However, increased porosity results in decreased material strength. The porosity and pore sizes that are ideal for porous implants are still controversial in the literature, complicating the justification of a design decision. Recently, metallic porous biomaterials have been proposed for load-bearing applications beyond surface coatings. This recent science lacks standards, but the Quality by Design (QbD) system can assist the design process in a systematic way. This study used the QbD system to explore the Quality Target Product Profile and Ideal Quality Attributes of additively manufactured titanium porous scaffolds for bone regeneration with a biomimetic approach. For this purpose, a total of 807 experimental results extr...

Research paper thumbnail of Challenges in laser-assisted milling of titanium alloys

International Journal of Extreme Manufacturing, 2021

Several detailed studies have comprehensively investigated the benefits and limitations of laser-... more Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining (LAM) of titanium alloys. These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life. This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process. The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.

Research paper thumbnail of Tool wear mechanisms involved in crater formation on uncoated carbide tool when machining Ti6Al4V alloy

The International Journal of Advanced Manufacturing Technology, 2015

When machining titanium alloys at cutting speeds higher than 60 m/min using cemented carbide cutt... more When machining titanium alloys at cutting speeds higher than 60 m/min using cemented carbide cutting tools, the tool wears out rapidly. With the ever-increasing use of titanium alloys, it is essential to address this issue of rapid tool wear in order to reduce manufacturing costs. Therefore, the intention of this study was to investigate all possible tool wear mechanisms involved when using uncoated carbide cutting tools to machine Ti6Al4V titanium alloy at a cutting speed of 150 m/min under dry cutting conditions. Adhesion, diffusion, attrition, and abrasion were found to be the mechanisms associated with the cratering of the rake surface of the cutting tool. The plastic deformation of the cutting edge was also noticed which resulted in weakening of the rake surface and clear evidence has been presented. Based on this evidence, the process of the formation of the crater wear has been described in detail.

Research paper thumbnail of Microstructure and hardness characterisation of laser coatings produced with a mixture of AISI 420 stainless steel and Fe-C-Cr-Nb-B-Mo steel alloy powders

Surface and Coatings Technology, 2016

Fe-C-Cr-Nb-B-Mo alloy powder and AISI 420 SS powder are deposited using laser cladding to increas... more Fe-C-Cr-Nb-B-Mo alloy powder and AISI 420 SS powder are deposited using laser cladding to increase the hardness for wear resistant applications. Mixtures from 0 to 100 wt.% were evaluated to understand the effect on the elemental composition, microstructure, phases, and microhardness. The mixture of carbon, boron and niobium in the Fe-C-Cr-Nb-B-Mo alloy powder introduces complex carbides into a Fe-based matrix of AISI 420 SS which increases its hardness. Hardness increased linearly with increasing Fe-C-Cr-Nb-B-Mo alloy, but substantial micro-cracking was observed in the clad layer at additions of 60 wt.% and above; related to a transition from a hypoeutectic alloy containing α-Fe/α' dendrites with an (Fe,Cr)2B and γ-Fe eutectic to primary and continuous carbo-borides M2B (where M represents Fe and Cr) and M23(B,C)6 carbides (where M represents Fe, Cr, Mo) with MC particles (where M represents Nb and Mo). The highest average hardness, for an alloy without micro-cracking, of 952 HV was observed in a 40 wt.% alloy. High stress abrasive scratch testing was conducted on all alloys at various loads (500, 1500, 2500 N). Alloy content was found to have a strong effect on the wear mode and the abrasive wear rate, and the presence of micro-cracks was detrimental to abrasive wear resistance.

Research paper thumbnail of Numerical and Experimental Investigation of the Heat-Affected Zone in a Laser-Assisted Machining of Ti-6 Al-4 V Alloy Process

The aim of this work is to develop a 3-D transient finite element model for a moving Gaussian las... more The aim of this work is to develop a 3-D transient finite element model for a moving Gaussian laser heat source to predict the depth of the heat-affected zone (HAZ) and temperature distribution in a Ti6Al4V alloy workpiece. It is found that the temperature profile and depth of HAZ are strongly dependent on the parameters of the laser beam. The thermal model simulations are compared with results produced by experimental work and these show close agreement. Introduction Titanium alloys have been widely used in the aerospace, biomedical and automotive industries because of their high strength-to-weight ratio and superior corrosion resistance. However, it is very difficult to machine these alloys due to their poor machinability [1]. Laser assisted machining (LAM) is a new and innovative manufacturing process that has been investigated as an alternative to conventional machining of hard and/or difficult-to-process materials such as titanium alloys [2-7]. This heat-assisted process induce...

Research paper thumbnail of Insights into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

Metals

New metastable β titanium alloys are receiving increasing attention due to their excellent biomec... more New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study, machining chip microstructure has been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400–600 °C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20–50 nm, while further from the interface the β grains become highl...

Research paper thumbnail of Effect of laser beam on the chip formation in machining of titanium alloys

International Congress on Applications of Lasers & Electro-Optics

Research paper thumbnail of Effect of tool wear evolution on chip formation during dry machining of Ti-6Al-4V alloy

International Journal of Machine Tools and Manufacture

Research paper thumbnail of Correlation between melt pool temperature and clad formation in pulsed and continuous wave Nd:YAG laser cladding of stellite 6

Pacific International Conference on Applications of Lasers and Optics

The melt pool temperature in pulsed laser cladding of stellite 6 was measured with a two-colour p... more The melt pool temperature in pulsed laser cladding of stellite 6 was measured with a two-colour pyrometer. The pulse peak temperature (p T), durations when the melt and continuous wave (CW) laser cladding of stellite 6. Comparison between the experimental data and prediction has been made. Thick clad layer with low level of dilution requires higher value of the product of f t 1 ⋅ , longer beam interaction time (τ) and large M D .

Research paper thumbnail of Insights Into Machining of a β Titanium Biomedical Alloy from Chip Microstructures

New metastable β titanium alloys are receiving increasing attention due to their excellent biomec... more New metastable β titanium alloys are receiving increasing attention due to their excellent biomechanical properties and machinability is critical to their uptake. In this study machining chip microstructure have been investigated to gain an understanding of strain and temperature fields during cutting. For higher cutting speeds, ≥60 m/min, the chips have segmented morphologies characterised by a serrated appearance. High levels of strain in the primary shear zone promote formation of expanded shear band regions between segments which exhibit intensive refinement of the β phase down to grain sizes below 100 nm. The presence of both α and β phases across the expanded shear band suggests that temperatures during cutting are in the range of 400-600°C. For the secondary shear zone, very large strains at the cutting interface result in heavily refined and approximately equiaxed nanocrystalline β grains with sizes around 20-50 nm, while further from the interface the β grains become highly elongated in the shear direction. An absence of the α phase in the region immediately adjacent to the cutting interface indicates recrystallization during cutting and temperatures in excess of the 720°C β transus temperature.

Research paper thumbnail of Experimental investigation of cutting forces and tool wear during laser-assisted milling of Ti-6Al-4V alloy

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigate... more The improvement of machinability during laser-assisted milling of Ti-6Al-4V alloy was investigated. The effects of laser processing and milling parameters on cutting forces and tool wear have been examined. It is found that local heating and softening of the workpiece by the laser beam in front of the cutting tool significantly reduced the cutting forces, especially the force in the feed direction during up-cut milling. Laser power, tool-beam distance, depth of cut and cutting speed are the parameters influencing the change of feed force during laser-assisted milling. Analysis of the workpiece temperature rise due to laser beam heating shows that the feed force is strongly dependent on the workpiece temperature in front of the cutting zone; significant reduction of feed force occurred when the temperature in front of the cutting zone was in the range 200-450 C. Edge chipping is found to be the tool failure mode for both conventional milling and laser-assisted milling. A significant improvement in tool life during laser-assisted milling was obtained when the workpiece temperature in front of the cutting zone was at an optimum value. Compressed air was used to remove the chip from the cutting tool, which made the milling process more effective. The optimum workpiece temperature in front of the cutting zone with compressed air delivered through the spindle is about 350 C, higher than that with compressed air delivered through a stationary nozzle (about 230 C). The maximum tool life in the former case is much longer than that in the latter case.

Research paper thumbnail of Effect of tool wear on chip formation during dry machining of Ti-6Al-4V alloy, part 1: Effect of gradual tool wear evolution

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

Geometric features of the segmented chip have been investigated along with the volume of material... more Geometric features of the segmented chip have been investigated along with the volume of material removed at a cutting speed at which tool wear is characterized by the gradual development of flank wear when cutting Ti-6Al-4V alloy. The chip geometric variables varied with an increase in the volume of material removed as the combined effect of change in tool’s geometry and increase in cutting temperature. Plastic deformation dimples were observed as periodical regions on the machined surface, a row on each undeformed surface and region on the top of the slipping surface of the segmented chip when cutting with new tool; these dimples on the undeformed surface and machined surface are elongated in the direction of chip flow. All these dimples became less with an increase in the volume of material removed and almost disappeared when the chip was removed with the worn tool at the end of its life. A model of segmented chip formation process has been proposed to satisfactorily explain the ...

Research paper thumbnail of A case-study on the mechanism of flank wear during laser-assisted machining of a titanium alloy

International Journal of Machining and Machinability of Materials