The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages...The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages： the first stage involves rapid dissolution of eutectic β （Mg 17 Al 12 ） phase, homogenization and coarsening, and the second stage is regarded as normal grain growth consisting of primary α-Mg particles （primary particles） and secondary α-Mg grains （secondary grains）. In the first stage, the dissolution completes in a quite short time because the fine β phase can quickly dissolve into the small-sized secondary grains. The homogenization of Al element needs relatively long time. Simultaneously, the microstructure morphology and average grain size obviously change. The first stage sustains approximately 1 h when it is solutionized at 395 ℃ Comparatively, the second stage needs very long time and the microstructure evolves quite slowly as a result of low Al content gradient and thus low diffusivity of Al element after the homogenization of the first stage. The growth model of primary particles obeys power function while that of the secondary grains follows the traditional growth equation in the first stage. In the second stage, both of the primary particles and secondary grains behave a same model controlled by diffusion along grain boundaries and through crystal lattice.展开更多
Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The inf...Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.展开更多
基金Project(G2007CB613706)supported by the National Basic Research Program of ChinaProject supported by the Development Program for Outstanding Young Teachers in Lanzhou University of Technology, ChinaProject(SKL03004)supported by the Opening Foundation of State Key Laboratory of Advanced Nonferrous Materials, China
文摘The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages： the first stage involves rapid dissolution of eutectic β （Mg 17 Al 12 ） phase, homogenization and coarsening, and the second stage is regarded as normal grain growth consisting of primary α-Mg particles （primary particles） and secondary α-Mg grains （secondary grains）. In the first stage, the dissolution completes in a quite short time because the fine β phase can quickly dissolve into the small-sized secondary grains. The homogenization of Al element needs relatively long time. Simultaneously, the microstructure morphology and average grain size obviously change. The first stage sustains approximately 1 h when it is solutionized at 395 ℃ Comparatively, the second stage needs very long time and the microstructure evolves quite slowly as a result of low Al content gradient and thus low diffusivity of Al element after the homogenization of the first stage. The growth model of primary particles obeys power function while that of the secondary grains follows the traditional growth equation in the first stage. In the second stage, both of the primary particles and secondary grains behave a same model controlled by diffusion along grain boundaries and through crystal lattice.
基金Project(2009AA03Z114)supported by the National High-tech Research and Development Program of ChinaProject supported by Tsinghua-Toyo R&D Center of Magnesium and Aluminum Alloys Processing Technology
文摘Standard mechanical test bars with a diameter of 6.4 mm and a gauge length of 50 mm were processed, and the microstructures of die cast AM60B alloy under different die casting process parameters were observed. The influences of the slow shot speed, the fast shot speed and the biscuit thickness on the externally solidified crystals （ESCs） were investigated. With the increase of the biscuit thickness, the number of the ESCs in the cast samples decreases. Under a low slow shot speed, larg ESCs are found in the cast structure and a high fast shot speed results in more spherical ESCs. The relationships between ESCs and process parameters were also discussed.
