A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube ...A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 ℃ and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 ℃ and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio（MER） of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.展开更多
The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and t...The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%.The microstructures during the deformation process were characterized.The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed.The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process.The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress.The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate.At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.展开更多
In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and ...In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and blank holder force(BHF) on formability was quantified using Taguchi design, analysis of variance(ANOVA) and mathematical statistics. The finite element(FE) model has been established in software Pamstamp for simulation and analysis of their effects on the minimum thickness and thickness variation of the hot-stamped component. The major factors influencing the minimum thickness of the hot-stamped part has been found to be BHF and friction coefficient with influence significance of 35.3% and 34.88%, respectively. Additionally, punch velocity and BHF affect the thickness deviation significantly with influence significance of 40.43% and 35.42%, respectively. Furthermore, a serious thinning occurs on the punch corner region of the hot-stamped cup when the BHF is larger than 2.4 kN. The thickness deviation of the hotformed cup has been found to be firstly decreased and then increased with the increase of punch velocity. Low friction coefficient between punch and blank led to crack at bottom centre of the cup. Moreover, different type, phenomenon and mechanism of defects occurring during hot stamping process, such as crack and wrinkling, were discussed. The crack mode was dimple-dominated ductile fracture, which was induced by micro-void nucleation, growth and coalescence.展开更多
基金Project(51775481)supported by the National Natural Science Foundation of ChinaProject(A2016002017)supported by the High-level Talents Program of Heibei Province,China
文摘A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 ℃ and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 ℃ and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio（MER） of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.
基金Project(50874049) supported by the National Natural Science Foundation of ChinaProject(2008DFB50020) supported by International Science and Technology Cooperation of Ministry of Science and Technology of China
文摘The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%.The microstructures during the deformation process were characterized.The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed.The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process.The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress.The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate.At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.
文摘In this study, a novel punch toolset was developed to investigate the hot stamping of AA6082-T4 sheet. The effect of the process parameters, including forming temperature, punching velocity, friction coefficient, and blank holder force(BHF) on formability was quantified using Taguchi design, analysis of variance(ANOVA) and mathematical statistics. The finite element(FE) model has been established in software Pamstamp for simulation and analysis of their effects on the minimum thickness and thickness variation of the hot-stamped component. The major factors influencing the minimum thickness of the hot-stamped part has been found to be BHF and friction coefficient with influence significance of 35.3% and 34.88%, respectively. Additionally, punch velocity and BHF affect the thickness deviation significantly with influence significance of 40.43% and 35.42%, respectively. Furthermore, a serious thinning occurs on the punch corner region of the hot-stamped cup when the BHF is larger than 2.4 kN. The thickness deviation of the hotformed cup has been found to be firstly decreased and then increased with the increase of punch velocity. Low friction coefficient between punch and blank led to crack at bottom centre of the cup. Moreover, different type, phenomenon and mechanism of defects occurring during hot stamping process, such as crack and wrinkling, were discussed. The crack mode was dimple-dominated ductile fracture, which was induced by micro-void nucleation, growth and coalescence.
