Hailiang YU - Academia.edu (original) (raw)

Papers by Hailiang YU

Materials Science and Engineering: A, 2016

Finite Element Analysis, 2010

Finite element method (FEM) has been widely employed for simulation of rolling problems, such as ... more Finite element method (FEM) has been widely employed for simulation of rolling problems, such as thermal field [1,2], stress-strain field [3], microstructure distribution [4], rolling force [5], rolling pressure distribution[6], plate view shape [7,8], roll deflection [9,10], tracing the evolution of macrosegregation [11]. As the development of FEM, there are three important ways for the application of FEM in analysis of rolling problems recently. Firstly, rapid FEM, and its on-line application [12-14]; secondly, coupled multi-scale FEM, macro -FEM & micro -FEM & crystal -FEM, coupled the macro-deformation and microstructure evolution and texture distribution [15-16]; third, tracing the defects in whole rolling processes [11, 18-21].

International Journal of Damage Mechanics, 2014

The size effect on the mechanism of fracture in ultrafine grained sheets is an unsolved problem i... more The size effect on the mechanism of fracture in ultrafine grained sheets is an unsolved problem in microforming. This paper describes a tensile test carried out to study the fracture behavior and the shear fracture angles of both rolled and aged ultrafine grained aluminum 6061 sheets produced by asymmetric cryorolling. A scanning electron microscope was used to observe the fracture surface. The finite element method was used to simulate the tensile test using the uncoupled Cockcroft-Latham and Tresca criteria and the coupled Gurson-Tvergaard-Needleman damage criterion. It was found that the shear fracture angle decreases gradually from 90 to 64 with an increasing number of passes. The results of simulations using the Gurson-Tvergaard-Needleman criterion show trends similar to the experimental ones. The paper also presents a discussion on the fracture mechanism and the size effect during the tensile test.

International Journal of Advanced Manufacturing Technology

Twin-roll strip casting is an effective technology to produce magnesium alloy strips economically... more Twin-roll strip casting is an effective technology to produce magnesium alloy strips economically. The aim of this work is to propose suitable (optimized) process parameters for manufacturing AZ61 strips using the twin-roll strip casting technology. Experiments on twin-roll strip casting of an AZ61 magnesium alloy were carried out. Temperature fields, fluid flow fields, and stress fields accompanying the process were simulated using thermal-fluid and thermal-mechanical finite element methods. The effects of casting speed and pouring temperature on temperature fields, fluid flow fields, and stress fields during the process were analyzed. It was found that the optimum pouring temperature should be in the range 690∼715 °C and the optimum casting speed in the range 2.3 and 2.5 m/min.

Materials Science Forum, 2007

By means of FISICO test, the cracking susceptibility of the 6061 aluminum was investigated, the e... more By means of FISICO test, the cracking susceptibility of the 6061 aluminum was investigated, the experimental results showed that it is prone to form crater crack under restraint condition comparison with that of the 3003 aluminum. So the crater fill-up technology need to be employed accordingly during the field welding. The strength, elongation percentage and hardness of the as welded joint was lowered 29.7%40%ď42% respectively, the former two is recovered to 73.4% and 81.7% of the base material respectively after natural aging 30days. This indicate that the natural aging treatment can remedy part of the property loss during the welding.

Steel Research International

Macrosegregation has a ring shape in continuous casting slab when electromagnetic stirring techno... more Macrosegregation has a ring shape in continuous casting slab when electromagnetic stirring technologies are used The mechanical properties of rolled products are affected by the distribution of macrosegregation in bars after rolling process It is of significance to reveal the change of distribution of macrosegregation rings in slab during the rolling process In this paper, the authors developed a finite element model to trace macrosegregation rings in slab during a rough rolling process with grooved roll of eleven passes according to industrial production The distributions of macrosegregation rings in slab after every rolling pass were obtained The calculated final distribution of macrosegregation rings were compared with the industrial production samples, they were in good agreement Finally, the authors focused on discussion how to control the distribution of macrosegregation rings in bars during rolling.

The International Journal of Advanced Manufacturing Technology, 2014

Internal cracks often appear in cast slabs, and their evolution during hot deformation directly a... more Internal cracks often appear in cast slabs, and their evolution during hot deformation directly affects the product quality. In this paper, the authors investigate the closure behavior of internal cracks during plate rolling using a finite element (FE) model that takes into account the roughness of the crack surface. Influences of the roughness and reduction ratio on the closure of cracks are analyzed. The simulated results show that the models with consideration of the initial crack roughness can be used to investigate the formation of residual voids around the crack after rolling. The simulation results are validated by experimental observations. Finally, we propose an explanation of the crack closure mechanism during rolling.

Materials Science and Engineering: A, 2014

A crystal plasticity finite element method (CPFEM) model has been developed to investigate the in... more A crystal plasticity finite element method (CPFEM) model has been developed to investigate the influence of indenter geometry on the mechanical behaviour and micro-texture evolution during nano-indentation of single crystal aluminium. The developed model has been validated by comparison with experimental observations. The numerical results show that indenter geometry influences the load-indentation depth curve, hardness and elastic modulus significantly. The surface profile, equivalent plastic strain distribution and micro-texture evolution during nano-indentation have been analysed in detail.

8 th Pacific Rim International Congress on Advanced Materials and Processing, 2013

In this paper, a survey of four relatively recent rolling technologies is presented. The merits a... more In this paper, a survey of four relatively recent rolling technologies is presented. The merits and drawbacks of each technique are examined. These techniques are: (1) Heated Roll Rolling, and the suitability of this technique for magnesium sheet production; (2) Asymmetric Cryorolling, which has potential for large-scale industrial production of nanostructural materials; (3) Variable-Gauge Rolling, used for production of flat products with variable thicknesses; and (4) Through-width Vibration Rolling, used for fabrication of ultrafine material sheets. Where possible, computer simulations of the rolling processes are described. Among the interesting simulation results obtained is the finding that the shear strain distribution in strips produced using the Through-width Vibration Rolling technology is more uniform and shows higher shear strain values, when compared with the conventional rolling technology.

Scientific reports, 2015

It is well known that when coarse-grained metals undergo severe plastic deformation to be transfo... more It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.

PloS one, 2014

Parts produced by microforming are becoming ever smaller. Similarly, the foils required in micro-... more Parts produced by microforming are becoming ever smaller. Similarly, the foils required in micro-machines are becoming ever thinner. The asymmetric rolling technique is capable of producing foils that are thinner than those produced by the conventional rolling technique. The difference between asymmetric rolling and conventional rolling is the 'cross-shear' zone. However, the influence of the cross-shear zone on the minimum achievable foil thickness during asymmetric rolling is still uncertain. In this paper, we report experiments designed to understand this critical influencing factor on the minimum achievable thickness in asymmetric rolling. Results showed that the minimum achievable thickness of rolled foils produced by asymmetric rolling with a rolling speed ratio of 1.3 can be reduced to about 30% of that possible by conventional rolling technique. Furthermore, the minimum achievable thickness during asymmetric rolling could be correlated to the cross-shear ratio, which...

PloS one, 2014

A new experimental method, called the 'hole filling method', is proposed to simulate the ... more A new experimental method, called the 'hole filling method', is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to...

Materials Science and Engineering: A, 2015

Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filt... more Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filtered Arc Deposition System (FADS). Nanoindentation tests were performed on both coatings. The multilayer TiCN/Ti coating exhibited better ductility than the monolayer TiCN coating. The lattice constants of the coatings were characterized by X-ray diffraction. Transmission Electron Microscopy (TEM) was used to investigate the fracture behavior of the coatings. Inter-columnar, inclined and lateral cracks were found to be the dominant crack modes in the monolayer TiCN coatings while small bending crack and radial crack were the dominant crack modes in the multilayer TiCN/Ti coatings. The Finite Element Method (FEM) was used to simulate the indentation process. It was found that the Ti interlayer in the multilayer TiCN/Ti coating could efficiently suppress the fracture, which is responsible for the improved ductility of the multilayer TiCN/Ti coating.

Materials Science Forum, 2012

Blades are key part of hydro turbines, which often distorts during heat treatment process for the... more Blades are key part of hydro turbines, which often distorts during heat treatment process for their special structures. In this paper, thermal-fluid finite element simulation of the forced air cooling process of a blade casting was carried out under a variety of distances between fans and blades, air speeds, groups of fans and circumstance temperatures. The temperature fields of blade castings were obtained. A novel parameter, temperature difference between surfaces of castings along thickness direction, was proposed to analyze the distortion of blade castings. The distortion behavior of blade castings with martensitic stainless steel were discussed, which is in good agreement with distortion regularity of the experimental ones. The temperature differences between blade casting surfaces are always greater than zero, resulting in distortion which could be divided into three stages. Finally, we focused on discussing the control methods of distortion behavior of blade castings which could be operated in actual production.

Philosophical Magazine Letters, 2014

We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate an... more We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate annealed at 873 K for seven days. The residual dislocation density reaches 7.5 × 10 14 m −2 , higher than that in aluminum after severe plastic deformation processes such as accumulative roll bonding and high-pressure torsion. It is proposed that the high residual dislocation density may result from obstruction of the movement of TiAl 3 nanoparticles by the grain boundary and Ti atoms conglomerating at vacancies distributed in the aluminium matrix at a high temperature for a sufficient time to allow a relatively stable crystal.

Twin-roll strip casting is a concerned technology for economically producing magnesium alloys she... more Twin-roll strip casting is a concerned technology for economically producing magnesium alloys sheets. In this paper, numerical simulation of the twin-roll strip casting of an AZ61 magnesium alloy was carried out and the optimal process parameters were obtained. Then, under the conditions obtained through simulation, AZ61 strips of good surface quality were successfully manufactured. The microstructure of the alloy by twin-rolled strip casting is obvious refined compared with that by conventional casting.

Pricm 7, Pts 1-3, 2010

Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their... more Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their cooling is not well controlled. The coupled analysis of forced air flow and heat transfer in normalizing process of a heavy turbine band runner casting with outer diameter of 8000 mm was carried out by using ANSYS software. The band undergoes significant deformation because of uneven cooling resulted by uneven air flow around it during normalizing. The forced air flow pattern is a key factor which influences the cooling uniformity and efficiency. It is optimized by adjusting the cooling fans' orientation relative to the casting to form cyclone around it. Consequently, cooling uniformity is improved to avoid deformation.

Manufacturing Processes and Systems, Pts 1-2, 2011

Materials Science and Engineering: A, 2016

Finite Element Analysis, 2010

Finite element method (FEM) has been widely employed for simulation of rolling problems, such as ... more Finite element method (FEM) has been widely employed for simulation of rolling problems, such as thermal field [1,2], stress-strain field [3], microstructure distribution [4], rolling force [5], rolling pressure distribution[6], plate view shape [7,8], roll deflection [9,10], tracing the evolution of macrosegregation [11]. As the development of FEM, there are three important ways for the application of FEM in analysis of rolling problems recently. Firstly, rapid FEM, and its on-line application [12-14]; secondly, coupled multi-scale FEM, macro -FEM & micro -FEM & crystal -FEM, coupled the macro-deformation and microstructure evolution and texture distribution [15-16]; third, tracing the defects in whole rolling processes [11, 18-21].

International Journal of Damage Mechanics, 2014

The size effect on the mechanism of fracture in ultrafine grained sheets is an unsolved problem i... more The size effect on the mechanism of fracture in ultrafine grained sheets is an unsolved problem in microforming. This paper describes a tensile test carried out to study the fracture behavior and the shear fracture angles of both rolled and aged ultrafine grained aluminum 6061 sheets produced by asymmetric cryorolling. A scanning electron microscope was used to observe the fracture surface. The finite element method was used to simulate the tensile test using the uncoupled Cockcroft-Latham and Tresca criteria and the coupled Gurson-Tvergaard-Needleman damage criterion. It was found that the shear fracture angle decreases gradually from 90 to 64 with an increasing number of passes. The results of simulations using the Gurson-Tvergaard-Needleman criterion show trends similar to the experimental ones. The paper also presents a discussion on the fracture mechanism and the size effect during the tensile test.

International Journal of Advanced Manufacturing Technology

Twin-roll strip casting is an effective technology to produce magnesium alloy strips economically... more Twin-roll strip casting is an effective technology to produce magnesium alloy strips economically. The aim of this work is to propose suitable (optimized) process parameters for manufacturing AZ61 strips using the twin-roll strip casting technology. Experiments on twin-roll strip casting of an AZ61 magnesium alloy were carried out. Temperature fields, fluid flow fields, and stress fields accompanying the process were simulated using thermal-fluid and thermal-mechanical finite element methods. The effects of casting speed and pouring temperature on temperature fields, fluid flow fields, and stress fields during the process were analyzed. It was found that the optimum pouring temperature should be in the range 690∼715 °C and the optimum casting speed in the range 2.3 and 2.5 m/min.

Materials Science Forum, 2007

By means of FISICO test, the cracking susceptibility of the 6061 aluminum was investigated, the e... more By means of FISICO test, the cracking susceptibility of the 6061 aluminum was investigated, the experimental results showed that it is prone to form crater crack under restraint condition comparison with that of the 3003 aluminum. So the crater fill-up technology need to be employed accordingly during the field welding. The strength, elongation percentage and hardness of the as welded joint was lowered 29.7%40%ď42% respectively, the former two is recovered to 73.4% and 81.7% of the base material respectively after natural aging 30days. This indicate that the natural aging treatment can remedy part of the property loss during the welding.

Steel Research International

Macrosegregation has a ring shape in continuous casting slab when electromagnetic stirring techno... more Macrosegregation has a ring shape in continuous casting slab when electromagnetic stirring technologies are used The mechanical properties of rolled products are affected by the distribution of macrosegregation in bars after rolling process It is of significance to reveal the change of distribution of macrosegregation rings in slab during the rolling process In this paper, the authors developed a finite element model to trace macrosegregation rings in slab during a rough rolling process with grooved roll of eleven passes according to industrial production The distributions of macrosegregation rings in slab after every rolling pass were obtained The calculated final distribution of macrosegregation rings were compared with the industrial production samples, they were in good agreement Finally, the authors focused on discussion how to control the distribution of macrosegregation rings in bars during rolling.

The International Journal of Advanced Manufacturing Technology, 2014

Internal cracks often appear in cast slabs, and their evolution during hot deformation directly a... more Internal cracks often appear in cast slabs, and their evolution during hot deformation directly affects the product quality. In this paper, the authors investigate the closure behavior of internal cracks during plate rolling using a finite element (FE) model that takes into account the roughness of the crack surface. Influences of the roughness and reduction ratio on the closure of cracks are analyzed. The simulated results show that the models with consideration of the initial crack roughness can be used to investigate the formation of residual voids around the crack after rolling. The simulation results are validated by experimental observations. Finally, we propose an explanation of the crack closure mechanism during rolling.

Materials Science and Engineering: A, 2014

A crystal plasticity finite element method (CPFEM) model has been developed to investigate the in... more A crystal plasticity finite element method (CPFEM) model has been developed to investigate the influence of indenter geometry on the mechanical behaviour and micro-texture evolution during nano-indentation of single crystal aluminium. The developed model has been validated by comparison with experimental observations. The numerical results show that indenter geometry influences the load-indentation depth curve, hardness and elastic modulus significantly. The surface profile, equivalent plastic strain distribution and micro-texture evolution during nano-indentation have been analysed in detail.

8 th Pacific Rim International Congress on Advanced Materials and Processing, 2013

In this paper, a survey of four relatively recent rolling technologies is presented. The merits a... more In this paper, a survey of four relatively recent rolling technologies is presented. The merits and drawbacks of each technique are examined. These techniques are: (1) Heated Roll Rolling, and the suitability of this technique for magnesium sheet production; (2) Asymmetric Cryorolling, which has potential for large-scale industrial production of nanostructural materials; (3) Variable-Gauge Rolling, used for production of flat products with variable thicknesses; and (4) Through-width Vibration Rolling, used for fabrication of ultrafine material sheets. Where possible, computer simulations of the rolling processes are described. Among the interesting simulation results obtained is the finding that the shear strain distribution in strips produced using the Through-width Vibration Rolling technology is more uniform and shows higher shear strain values, when compared with the conventional rolling technology.

Scientific reports, 2015

It is well known that when coarse-grained metals undergo severe plastic deformation to be transfo... more It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.

PloS one, 2014

Parts produced by microforming are becoming ever smaller. Similarly, the foils required in micro-... more Parts produced by microforming are becoming ever smaller. Similarly, the foils required in micro-machines are becoming ever thinner. The asymmetric rolling technique is capable of producing foils that are thinner than those produced by the conventional rolling technique. The difference between asymmetric rolling and conventional rolling is the 'cross-shear' zone. However, the influence of the cross-shear zone on the minimum achievable foil thickness during asymmetric rolling is still uncertain. In this paper, we report experiments designed to understand this critical influencing factor on the minimum achievable thickness in asymmetric rolling. Results showed that the minimum achievable thickness of rolled foils produced by asymmetric rolling with a rolling speed ratio of 1.3 can be reduced to about 30% of that possible by conventional rolling technique. Furthermore, the minimum achievable thickness during asymmetric rolling could be correlated to the cross-shear ratio, which...

PloS one, 2014

A new experimental method, called the 'hole filling method', is proposed to simulate the ... more A new experimental method, called the 'hole filling method', is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to...

Materials Science and Engineering: A, 2015

Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filt... more Monolayer TiCN and multilayer TiCN/Ti coatings were deposited on the surface of Ti using the Filtered Arc Deposition System (FADS). Nanoindentation tests were performed on both coatings. The multilayer TiCN/Ti coating exhibited better ductility than the monolayer TiCN coating. The lattice constants of the coatings were characterized by X-ray diffraction. Transmission Electron Microscopy (TEM) was used to investigate the fracture behavior of the coatings. Inter-columnar, inclined and lateral cracks were found to be the dominant crack modes in the monolayer TiCN coatings while small bending crack and radial crack were the dominant crack modes in the multilayer TiCN/Ti coatings. The Finite Element Method (FEM) was used to simulate the indentation process. It was found that the Ti interlayer in the multilayer TiCN/Ti coating could efficiently suppress the fracture, which is responsible for the improved ductility of the multilayer TiCN/Ti coating.

Materials Science Forum, 2012

Blades are key part of hydro turbines, which often distorts during heat treatment process for the... more Blades are key part of hydro turbines, which often distorts during heat treatment process for their special structures. In this paper, thermal-fluid finite element simulation of the forced air cooling process of a blade casting was carried out under a variety of distances between fans and blades, air speeds, groups of fans and circumstance temperatures. The temperature fields of blade castings were obtained. A novel parameter, temperature difference between surfaces of castings along thickness direction, was proposed to analyze the distortion of blade castings. The distortion behavior of blade castings with martensitic stainless steel were discussed, which is in good agreement with distortion regularity of the experimental ones. The temperature differences between blade casting surfaces are always greater than zero, resulting in distortion which could be divided into three stages. Finally, we focused on discussing the control methods of distortion behavior of blade castings which could be operated in actual production.

Philosophical Magazine Letters, 2014

We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate an... more We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate annealed at 873 K for seven days. The residual dislocation density reaches 7.5 × 10 14 m −2 , higher than that in aluminum after severe plastic deformation processes such as accumulative roll bonding and high-pressure torsion. It is proposed that the high residual dislocation density may result from obstruction of the movement of TiAl 3 nanoparticles by the grain boundary and Ti atoms conglomerating at vacancies distributed in the aluminium matrix at a high temperature for a sufficient time to allow a relatively stable crystal.

Twin-roll strip casting is a concerned technology for economically producing magnesium alloys she... more Twin-roll strip casting is a concerned technology for economically producing magnesium alloys sheets. In this paper, numerical simulation of the twin-roll strip casting of an AZ61 magnesium alloy was carried out and the optimal process parameters were obtained. Then, under the conditions obtained through simulation, AZ61 strips of good surface quality were successfully manufactured. The microstructure of the alloy by twin-rolled strip casting is obvious refined compared with that by conventional casting.

Pricm 7, Pts 1-3, 2010

Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their... more Hydraulic turbine band castings are susceptible to deformation in heat treatment process if their cooling is not well controlled. The coupled analysis of forced air flow and heat transfer in normalizing process of a heavy turbine band runner casting with outer diameter of 8000 mm was carried out by using ANSYS software. The band undergoes significant deformation because of uneven cooling resulted by uneven air flow around it during normalizing. The forced air flow pattern is a key factor which influences the cooling uniformity and efficiency. It is optimized by adjusting the cooling fans' orientation relative to the casting to form cyclone around it. Consequently, cooling uniformity is improved to avoid deformation.

Manufacturing Processes and Systems, Pts 1-2, 2011