In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was ...In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.展开更多
Explosive welding technique is widely used in many industries.This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods.Interlayer plays an important role...Explosive welding technique is widely used in many industries.This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods.Interlayer plays an important role to improve the welding quality and control energy loss during the collision process.In this paper,the Ti6Al4V plate was welded with a copper plate in the presence of a commercially pure titanium interlayer.Microstructure details of welded composite plate were observed through optical and scanning electron microscope.Interlayer-base plate interface morphology showed a wavy structure with solid melted regions inside the vortices.Moreover,the energy dispersive spectroscopy analysis in the interlayer-base interface reveals that there are some identified regions of different kinds of chemical equilibrium phases of CueTi,i.e.CuTi,Cu_(2)Ti,CuTi_(2),Cu_(4)Ti,etc.To study the mechanical properties of composite plates,mechanical tests were conducted,including the tensile test,bending test,shear test and Vickers hardness test.Numerical simulation of explosive welding process was performed with coupled Smooth Particle Hydrodynamic method,Euler and Arbitrary Lagrangian-Eulerian method.The multi-physics process of explosive welding,including detonation,jetting and interface morphology,was observed with simulation.Moreover,simulated plastic strain,temperature and pressure profiles were analysed to understand the welding conditions.Simulated results show that the interlayer base plate interface was created due to the high plastic deformation and localized melting of the parent plates.At the collision point,both alloys behave like fluids,resulting in the formation of a wavy morphology with vortices,which is in good agreement with the experimental results.展开更多
Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials a...Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials and also to minimize the effect of intermetallics formed at the joint interface. The process parameters that govern FWTPET process are plunge rate, rotational speed, plunge depth, axial load and flash trap profile. Among them, the flash trap profile of the tube has a significant influence on the joint integrity. Various flash trap profiles like vertical slots, holes, zig-zag holes, and petals were made on the titanium tube welded to the stainless steel tube plate. Macroscopic and microscopic studies reveal defect-free joints. The presence of copper interlayer and intermetallics was evident from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The microhardness survey was presented across and along the interface. A novel test procedure called “plunge shear test” was developed to evaluate the joint properties of the welded joints. The highest shear fracture load of 31.58 kN was observed on the sample having petals as flash trap profile. The sheared surfaces were further characterized using SEM for fractography.展开更多
Effects of various sintering methods such as spark plasma sintering(SPS), hot pressing(HP) and electric resistance sintering(ERS) on the microstructure and mechanical properties of commercial pure titanium(CP-Ti) powd...Effects of various sintering methods such as spark plasma sintering(SPS), hot pressing(HP) and electric resistance sintering(ERS) on the microstructure and mechanical properties of commercial pure titanium(CP-Ti) powder consolidations with particle size of <147 μm, <74 μm and <43 μm were studied. The smaller particle powders are densified to proceed at a higher rate. Dense titanium with relative density up to 99% is found to take place at 850 °C under 30 MPa of SPS and HP condition. However, in case of ERS, CP-Ti powders were densified almost at 950 °C under 30 MPa. The microstructure of sintered titanium is composed of equiaxed grains at 850-950 °C. The yield strength of sintered body composed of <43 μm powder is 858 MPa by using SPS at 850 °C under 30 MPa. When there is a higher content of small particle, the higher yield strength value is obtained both by using SPS and HP. However, when ERS is introduced, the highest yield strength is 441 MPa at 950 °C under 30 MPa, which shows much lower values than those by SPS and HP methods. ERS method takes much less sintering time compared with SPS and HP. Nevertheless, higher sintering temperature results in lower strength and elongation because of brittle fracture.展开更多
In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated...In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated in detail using Gleeble-1500 thermal mechanical simulator, universal testing machine and optical microscope （OM）. The compression deformation experimental data of commercially pure titanium （CP-Ti） were mapped to be a T vs lg diagram in which data fall into three distinct regions, i.e., three-stage work hardening, two-stage work hardening and flow softening, which can be separated by border lines at 17.5 and 15.4 for lg Z, where Z represents the Zener-Hollomon parameter. The deformation twin is found to have higher Z-value corresponding to the work hardening region. The differences in microstructures and mechanical properties for two kinds of billets indicate that forged billet consists of deformation twins and some twin intersections, and many twins cross the grain boundaries. However, nearly no twins can be seen in the microstructure of billet formed by rolling under optical microscope （OM）, but there are equiaxed and platelike grains. Tensile tests and Vickers hardness test indicate that yield strength, tensile strength and microhardness of the samples after forging are higher than those after rolling.展开更多
基金Projects(50905144,51275415)supported by the National Natural Science Foundation of ChinaProject supported by the Program for New Century Excellent Talents in University,ChinaProject(B08040)supported by the Program of Introducing Talents of Discipline to Universities,China("111"Project)
文摘In order to develop the warming bending technology of the large diameter thin-walled（LDTW） commercial pure titanium alloy CP-Ti tubes, the warm bending mechanism of the extrados and intrados of LDTW CP-Ti tubes was researched. By EBSD analysis and Vickers hardness test, the changes of microstructure and strength of the tubes at different bending temperatures of 293, 423 and 573 K, were analyzed. The results show： 1） The extrados of the bent tube deforms mainly by slip, along with few twinning, and the preferred orientation is similar to that of the initial tube; the intrados of the bent tube experiences compression deformation mainly by {1 012} tensile twinning, and the twinning makes the preferred orientation of wall materials change sharply. 2） The Vickers hardness values of both the extrados and intrados of the samples after bending increase greatly; the Vickers hardness values of the intrados are much higher than those of the extrados, and Vickers hardness values of the RD-TD planes are always higher than those of the RD-LD planes, which are related to the different deformation mechanisms.
文摘Explosive welding technique is widely used in many industries.This technique is useful to weld different kinds of metal alloys that are not easily welded by any other welding methods.Interlayer plays an important role to improve the welding quality and control energy loss during the collision process.In this paper,the Ti6Al4V plate was welded with a copper plate in the presence of a commercially pure titanium interlayer.Microstructure details of welded composite plate were observed through optical and scanning electron microscope.Interlayer-base plate interface morphology showed a wavy structure with solid melted regions inside the vortices.Moreover,the energy dispersive spectroscopy analysis in the interlayer-base interface reveals that there are some identified regions of different kinds of chemical equilibrium phases of CueTi,i.e.CuTi,Cu_(2)Ti,CuTi_(2),Cu_(4)Ti,etc.To study the mechanical properties of composite plates,mechanical tests were conducted,including the tensile test,bending test,shear test and Vickers hardness test.Numerical simulation of explosive welding process was performed with coupled Smooth Particle Hydrodynamic method,Euler and Arbitrary Lagrangian-Eulerian method.The multi-physics process of explosive welding,including detonation,jetting and interface morphology,was observed with simulation.Moreover,simulated plastic strain,temperature and pressure profiles were analysed to understand the welding conditions.Simulated results show that the interlayer base plate interface was created due to the high plastic deformation and localized melting of the parent plates.At the collision point,both alloys behave like fluids,resulting in the formation of a wavy morphology with vortices,which is in good agreement with the experimental results.
基金financial support provided by UGC-DAE-CSR (CSR-KN/CRS-04/201213/738) through fellowship
文摘Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials and also to minimize the effect of intermetallics formed at the joint interface. The process parameters that govern FWTPET process are plunge rate, rotational speed, plunge depth, axial load and flash trap profile. Among them, the flash trap profile of the tube has a significant influence on the joint integrity. Various flash trap profiles like vertical slots, holes, zig-zag holes, and petals were made on the titanium tube welded to the stainless steel tube plate. Macroscopic and microscopic studies reveal defect-free joints. The presence of copper interlayer and intermetallics was evident from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The microhardness survey was presented across and along the interface. A novel test procedure called “plunge shear test” was developed to evaluate the joint properties of the welded joints. The highest shear fracture load of 31.58 kN was observed on the sample having petals as flash trap profile. The sheared surfaces were further characterized using SEM for fractography.
基金Project(K0004130) supported by the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy,Korea
文摘Effects of various sintering methods such as spark plasma sintering(SPS), hot pressing(HP) and electric resistance sintering(ERS) on the microstructure and mechanical properties of commercial pure titanium(CP-Ti) powder consolidations with particle size of <147 μm, <74 μm and <43 μm were studied. The smaller particle powders are densified to proceed at a higher rate. Dense titanium with relative density up to 99% is found to take place at 850 °C under 30 MPa of SPS and HP condition. However, in case of ERS, CP-Ti powders were densified almost at 950 °C under 30 MPa. The microstructure of sintered titanium is composed of equiaxed grains at 850-950 °C. The yield strength of sintered body composed of <43 μm powder is 858 MPa by using SPS at 850 °C under 30 MPa. When there is a higher content of small particle, the higher yield strength value is obtained both by using SPS and HP. However, when ERS is introduced, the highest yield strength is 441 MPa at 950 °C under 30 MPa, which shows much lower values than those by SPS and HP methods. ERS method takes much less sintering time compared with SPS and HP. Nevertheless, higher sintering temperature results in lower strength and elongation because of brittle fracture.
基金Supported by the National Nature Science Foundation of China (50874086)Special Programs Foundation of Ministry of Education of Shaanxi Province (07JK307)the Nature Science Foundation of Shaanxi Province (2005E105)
文摘在室温,采用通道夹角为120°的变形模具对工业纯钛(Commercial Pure Titanium,CP-Ti)以Bc方式实施四道次ECAP(Equal Channel Angular Pressing)挤压变形,成功获得表面光滑无裂纹的变形试样。文中主要研究了工业纯钛在室温下进行ECAP多道次变形的组织结构演变,并测试了变形试样的力学性能。微观结构显示工业纯钛在室温下进行多道次ECAP变形时,只在前两道次产生了大量的变形孪晶,且随道次增加变形孪晶逐渐消失。最终获得的试样晶粒平均尺寸由最初的约28μm细化到约250nm,试样断裂强度和显微硬度分别提高到773和2486MPa,而试样仍保持较好的延伸率(可达16.8%)。
文摘In order to reveal the differences caused by forging and rolling process for titanium ingots, hot compression behavior, mechanical properties and the microstructures of forged billets and rolled ones were investigated in detail using Gleeble-1500 thermal mechanical simulator, universal testing machine and optical microscope （OM）. The compression deformation experimental data of commercially pure titanium （CP-Ti） were mapped to be a T vs lg diagram in which data fall into three distinct regions, i.e., three-stage work hardening, two-stage work hardening and flow softening, which can be separated by border lines at 17.5 and 15.4 for lg Z, where Z represents the Zener-Hollomon parameter. The deformation twin is found to have higher Z-value corresponding to the work hardening region. The differences in microstructures and mechanical properties for two kinds of billets indicate that forged billet consists of deformation twins and some twin intersections, and many twins cross the grain boundaries. However, nearly no twins can be seen in the microstructure of billet formed by rolling under optical microscope （OM）, but there are equiaxed and platelike grains. Tensile tests and Vickers hardness test indicate that yield strength, tensile strength and microhardness of the samples after forging are higher than those after rolling.
