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
An experimental Mg97Zn1Y2(molar fraction,%)alloy was produced by rolling the as-cast alloy.The microstructure of the alloy is composed of theα-Mg(also marked as 2H-Mg with reference to long-period stacking structure ...An experimental Mg97Zn1Y2(molar fraction,%)alloy was produced by rolling the as-cast alloy.The microstructure of the alloy is composed of theα-Mg(also marked as 2H-Mg with reference to long-period stacking structure according to hexagonal close packed structure)and long-period stacking(LPS)phase.Tensile tests of Mg97Zn1Y2 alloy in comparison with pure Mg were conducted.The fracture morphologies of the tensile specimens were characterized and the microstructures near fracture surface were observed.The results show that the rolled Mg97Zn1Y2 alloy shows a mixed fracture mode including dimples indicating a ductile fracture pattern and a small fraction of cleavage planes indicating a brittle fracture pattern,which is different from the single brittle fracture of the as-cast alloy.In addition,the plastic deformation is mainly from dislocations induced strain with small strengthening effect during plastic deformation in the as-cast Mg97Zn1Y2 alloy,and the strain hardening rate is similar to that of the as-cast pure magnesium.The deformation mechanism of Mg97Zn1Y2 alloy is different from that of the pure magnesium according to a metallographical observation that whether twins are found or not.The strengthening effect hardly exists in the rolled Mg97Zn1Y2 alloy under the same dislocations induced strain,which is different from that of the as-cast alloy with moderate strengthening effect.展开更多
Mg_(97)Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_(97)Zn_1Y_2 alloy with long-period stacking(LPS) structure is low...Mg_(97)Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_(97)Zn_1Y_2 alloy with long-period stacking(LPS) structure is lower than that of the commercial AZ91 alloy at room temperature.The microstructure evolutions in Mg_(97)Zn_1Y_2(molar fraction,%) alloys with LPS phase,processed by rolling and annealing the as-cast alloy and rapidly solidifying/melt-spinning and age treating at different temperatures respectively,were investigated by differential thermal analysis(DTA),X-ray diffraction(XRD),and laser optical microscopy(LOM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The evolutionary direction of microstructure prescribed by thermodynamics in the Mg_(97)Zn_1Y_2 alloy is reflected from experimental data of the as-cast alloy;and the actual evolution paths selected by kinetics are depicted in detail in the as-spun alloy and rolled alloy.The strong influences of thermodynamic nonequilibrium mechanism,which entails the factual complexity of microstructures typically during rapid solidification and deformation processing for strengthening the creep resistant magnesium alloy,are presented.展开更多
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.
基金Project(2009AA03Z114)supported by the National High-tech Research and Development Program of China
文摘An experimental Mg97Zn1Y2(molar fraction,%)alloy was produced by rolling the as-cast alloy.The microstructure of the alloy is composed of theα-Mg(also marked as 2H-Mg with reference to long-period stacking structure according to hexagonal close packed structure)and long-period stacking(LPS)phase.Tensile tests of Mg97Zn1Y2 alloy in comparison with pure Mg were conducted.The fracture morphologies of the tensile specimens were characterized and the microstructures near fracture surface were observed.The results show that the rolled Mg97Zn1Y2 alloy shows a mixed fracture mode including dimples indicating a ductile fracture pattern and a small fraction of cleavage planes indicating a brittle fracture pattern,which is different from the single brittle fracture of the as-cast alloy.In addition,the plastic deformation is mainly from dislocations induced strain with small strengthening effect during plastic deformation in the as-cast Mg97Zn1Y2 alloy,and the strain hardening rate is similar to that of the as-cast pure magnesium.The deformation mechanism of Mg97Zn1Y2 alloy is different from that of the pure magnesium according to a metallographical observation that whether twins are found or not.The strengthening effect hardly exists in the rolled Mg97Zn1Y2 alloy under the same dislocations induced strain,which is different from that of the as-cast alloy with moderate strengthening effect.
基金Projects(2006BA104B04-12006BAE04B07-3)supported by the National Science and Technology Supporting Program of China+1 种基金Project(2007KZ05)supported by the Science and Technology Supporting Project of Changchun City,ChinaProject supported by the"985Project"of Jilin University,China
文摘Mg_(97)Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_(97)Zn_1Y_2 alloy with long-period stacking(LPS) structure is lower than that of the commercial AZ91 alloy at room temperature.The microstructure evolutions in Mg_(97)Zn_1Y_2(molar fraction,%) alloys with LPS phase,processed by rolling and annealing the as-cast alloy and rapidly solidifying/melt-spinning and age treating at different temperatures respectively,were investigated by differential thermal analysis(DTA),X-ray diffraction(XRD),and laser optical microscopy(LOM),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The evolutionary direction of microstructure prescribed by thermodynamics in the Mg_(97)Zn_1Y_2 alloy is reflected from experimental data of the as-cast alloy;and the actual evolution paths selected by kinetics are depicted in detail in the as-spun alloy and rolled alloy.The strong influences of thermodynamic nonequilibrium mechanism,which entails the factual complexity of microstructures typically during rapid solidification and deformation processing for strengthening the creep resistant magnesium alloy,are presented.
