Comparisons of microstructure, thixoformability and mechanical properties of high performance wrought magnesium alloys reheated from the as-cast and extruded states
Comparisons of microstructure, thixoformability and mechanical properties of high performance wrought magnesium alloys reheated from the as-cast and extruded states
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DOI：
10.1016/j.jallcom.2013.08.218
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发表时间：
2014-01
影响因子：
6.2
通讯作者：
Qiang Chen;Bao-guo Yuan;Jun Lin;X. Xia;Zude Zhao;D. Shu
中科院分区：
文献类型：
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作者：
Qiang Chen;Bao-guo Yuan;Jun Lin;X. Xia;Zude Zhao;D. Shu
对铸态和挤压态Mg-Zn-Y-Zr合金二次加热后的固相晶粒尺寸、球化度、接触度和实际液相分数进行了表征和比较。进行触变成形试验以检查铸态和挤压态合金的触变成形性。还测定了由铸态和挤压态合金触变成形的Mg-Zn-Y-Zr合金的拉伸力学性能。从挤压合金再加热已被证明产生理想的，精细的半固态结构，其中完全球形的初级固体颗粒基本上没有夹带的液体。然而，铸态合金表现出不均匀的显微组织与大量的截留的液体，这是少的球形相比，在半固态挤压合金。挤压态合金在加热过程中的晶粒粗化速率低于铸态合金。在触变成形期间，尽管低的液体分数，细的和球状的固体晶粒是弱连接的并且在挤压合金中彼此滑动而没有任何塑性变形。因此，具有不均匀和粗固体晶粒的铸态合金不如挤压合金那样可触变。挤压态触变成形Mg-Zn-Y-Zr合金的拉伸力学性能优于铸态触变成形Mg-Zn-Y-Zr合金。
The solid grain size, degree of spheroidization, contiguity and practical liquid fraction of Mg–Zn–Y–Zr alloys reheated from the as-cast and extruded states are characterized and compared. Thixoforming tests are performed to examine thixoformability of the as-cast and extruded alloys. Tensile mechanical properties for Mg–Zn–Y–Zr alloys thixoformed from the as-cast and extruded alloys are also determined. Reheating from the extruded alloy has been shown to produce ideal, fine semi-solid structures, in which completely spheroidal primary solid grains are essentially free of entrapped liquid. However, the as-cast alloy exhibits non-uniform microstructures with a large amount of entrapped liquid, which are less spheroidal compared with the extruded alloy in the semi-solid state. The grain coarsening rate is relatively low in the extruded alloy than that in the as-cast alloy during reheating. During thixoforming, despite the low liquid fraction, the fine and spheroidal solid grains are weakly connected and slide over each other without any plastic deformation in the extruded alloy. Therefore, the as-cast alloy which has heterogeneous and coarse solid grains is not as thixoformable as the extruded alloy. The tensile mechanical properties for Mg–Zn–Y–Zr alloys thixoformed from the extruded alloy are better than those of Mg–Zn–Y–Zr alloys thixoformed from the as-cast alloy.