中文摘要：

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。

英文摘要：

Semi-solid 2024 aluminum alloy billet was prepared by recrystallization and partial remelting technology. Microstructure evolution was observed at different remelting temperature and holding time, and effects of processing parameters on grain size and spheroidization rate were analyzed. Based on thixo-forming casting, the difference of mechanical properties was described at varied position on the samples with different billet height. The results show that microstructure of the billet gradually undergoes the disappearance of extruded fibrous tissue, the generation of a-A1 recrystallized grains and the spheroidization and growth of a-A1 grains with increasing in holding time, and the process is accelerated with the remelting temperature increase. The size and spheroidization rate of the semi-solid grains are in- creased with the increase of remelting temperature and holding time. The average grain size with approximately 75 μm and spheroidized rate of 0.74 can be obtained at 613-621 ℃ for 20-30 rain, and the ten sile strength of the thixoforming parts can be reached up to 383 MPa. The tensile strength exbibits greatly different at different position due to the parts shape and forming characteristics.