(清華大學 機械工程系， 北京 100084)
摘 要: 通過重熔化學成分相同的AZ91D壓鑄件和鑄錠， 研究了爐料組織對鎂合金AZ91D金相形貌、 晶粒組織及力學性能的影響。 結果表明： 與鑄錠重熔后相比， 壓鑄件重熔后共晶體的離異程度較大， 平均晶粒尺寸較小； 經(jīng)過相同保溫時間， 壓鑄件重熔后的抗拉強度、 屈服強度及斷裂延伸率均較高； 隨保溫時間的延長， 兩種爐料重熔后的力學性能均得到了提高。 采用DTA分析了爐料重熔后的凝固過程， 凝固過程中過冷度較小是壓鑄件重熔后晶粒尺寸小于鑄錠重熔后晶粒尺寸的熱力學原因。
關鍵字: 爐料組織; AZ91D; 晶粒組織; 力學性能; DTA
（Department of Mechanical Engineering, Tsinghua University,
Beijing 100084, China）
Abstract: The effect of heredity on structure and properties of AZ91D alloy was investigated using ingots and rejected die-casting parts with the same composition as a furnace charge. After melting the charge, the melts were held for 15, 35 and 65 min at 720 ℃ and poured into a preheated metal mould. Solidification of re-melted furnace charge was analyzed by DTA. The results show that the different furnace charges show the noticeable difference in the grain size of the alloys and tensile properties; the mean grain size of the samples produced from the die-casting parts is smaller than those produced from the ingots for all holding times. The ultimate tensile strength, yield strength and elongation are correspondingly better for the samples made of the die-casting parts. As the holding time increases, the tensile properties of the samples, made of both kinds of the furnace charge, slightly improve. The grain size also does not noticeably vary with the increase in the holding time.
Key words: heredity; AZ91D; grain structure; tensile properties
