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采用再结晶与重熔法制备了2024铝合金半固态坯料,研究了不同重熔温度和保温时间下坯料的微观组织演变,以及工艺参数对晶粒尺寸和球化程度的影响。通过触变挤压铸造成形试验,分析了不同坯料高度下制件不同位置的力学性能差异。结果表明,坯料的微观组织随着保温时间的延长逐渐演变为挤压态纤维组织的消失、α-Al再结晶晶粒的初生和其球化与长大,且该过程随重熔温度的升高而加快;半固态球状晶粒的尺寸和球化程度均随重熔温度和保温时间的增加而变大;最佳工艺参数为613~621℃时保温20~30min,此时晶粒平均直径约为75μm,圆整度约为0.74。在此工艺参数下,触变成形制件的抗拉强度可达383MPa。
The 2024 aluminum alloy semi-solid billet was prepared by recrystallization and remelting. The microstructure evolution of the billet under different remelting temperature and holding time, and the effect of technological parameters on the grain size and spheroidization were studied. Through the thixotropic extrusion casting forming test, the different mechanical properties of the workpiece at different blank heights were analyzed. The results show that the microstructure of the blank gradually evolves as the disappearance of the extruded fibrous tissue, the primary and spheroidization and growth of α-Al recrystallized grains with the increase of holding time, The size and the degree of spheroidization of the semisolid spherical grains became larger with the increase of the remelting temperature and the holding time. The best parameters were the temperature of 6-13 ~ 621 ℃ for 20 ~ 30min, when the average grain diameter About 75 μm, roundness of about 0.74. In this process parameters, thixoformed parts tensile strength up to 383MPa.