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研究了挤压Mg-2Zn-0.5Y(at%)合金在半固态等温处理过程中的微观组织演变规律。结果表明:挤压态的Mg-2Zn-0.5Y合金包含α-Mg,Mg3-Zn6-Y1(I-Phase)和Mg3-Zn3-Y2(W-phase)3种物相,并且α-Mg的平均晶粒尺寸为7μm。在温度为793 K的半固态等温热处理过程中,晶粒不断长大,直到保温时间达到4.0 min时才出现液相。随着等温处理温度和时间的增加,α-Mg固相颗粒不断长大,并且逐步被液相分离;同时,出现在晶界的液相与颗粒内部的液滴都在不断地增多。研究还发现,当固相率较高时,晶粒间的合并机制与固相颗粒再熔化机制同时起主导作用;然而当固相率较低时,Ostwald熟化机制是主要的粗化机制,同时也可以观察到晶粒间的合并。
The microstructure evolution of extruded Mg-2Zn-0.5Y (at%) alloy during semi-solid isothermal treatment was studied. The results show that the as-extruded Mg-2Zn-0.5Y alloy contains three phases α-Mg, Mg3-Zn6-Y1 (I-Phase) and Mg3-Zn3-Y2 The average grain size is 7 μm. During the semi-solid isothermal heat treatment at a temperature of 793 K, the grains grew up and the liquid phase did not appear until the holding time reached 4.0 min. As the temperature and time of isothermal treatment increase, α-Mg solid particles grow up and are gradually separated by liquid phase. At the same time, the liquid phase appearing at the grain boundary and the droplets inside the particles are continuously increasing. The study also found that when the solid fraction is high, the intergranular merging mechanism plays a leading role simultaneously with the solid particle remelting mechanism. However, the Ostwald ripening mechanism is the main coarsening mechanism when the solid fraction is low, Grain-to-grain consolidation can also be observed.