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采用不同固溶温度及保温时间,研究了SiC p增强AZ91D镁合金组织演变及硬度变化行为。结果表明,随固溶温度提高,铸态组织中连续网状β相逐渐消失,汉字状Mg2Si相发生熔断,球化速度加快,400℃时晶界清晰。400℃×16h固溶时,不稳定β相几乎完全固溶至基体中,汉字状Mg2Si球化效果最佳,Al8Mn5相未发生明显变化。400℃×20h固溶后,Mg2Si球化趋势开始减弱,晶粒尺寸出现显著增加。结果表明,β相的消失和Mg2Si相的球化导致合金硬度发生连续下降。400℃×16h后由于固溶强化效果的增加,合金硬度有所提高。
Different solid solution temperature and holding time were used to study the microstructure evolution and hardness variation of SiC p reinforced AZ91D magnesium alloy. The results show that with the increase of solution temperature, the continuous reticulated β phase in the as-cast microstructure gradually disappears. The Chinese character Mg2Si phase melts and the spheroidization accelerates. The grain boundaries are clear at 400 ℃. At 400 ℃ for 16h, the unstable β phase is almost completely dissolved into the matrix. The Chinese character Mg2Si has the best spheroidization effect and the Al8Mn5 phase does not change obviously. After the solid solution at 400 ℃ for 20h, the spheroidization of Mg2Si begins to weaken and the grain size increases obviously. The results show that the disappearance of the β phase and the spheroidization of the Mg2Si phase lead to the continuous decrease of the hardness of the alloy. After 400 ℃ × 16h, the hardness of alloy increased due to the increase of solid solution strengthening effect.