【摘要】 以汽车差速器支架为对象，研究了不同浇注温度下近液相线挤压铸造AZ91D镁合金的组织及力学性能。结果表明，浇注温度由595℃升至665℃时，合金内部球状晶逐渐长大成蔷薇状晶，平均晶粒尺寸由21.02μm增大到58.13μm。第二相β-Mg17Al12的含量从18.55%提高到49.72%，且分布均匀性逐渐降低。浇注温度较低（595℃和605℃）时，合金拉伸断口存在大量韧窝和小面积的解理平面；随着浇注温度提高，断口的韧窝数量、解理台阶逐渐减少。浇注温度为605℃时，合金的抗拉强度为229.2 MPa，伸长率为3.16%，均达到了最大值。更多还原

【Abstract】 Taking the automobile differential supportor as object, the microstructure and mechanical properties of AZ91D alloy were investigated under different near-liquidus squeeze casting temperatures. The results indicate that when the pouring temperature is increased from 595 ℃ to 665 ℃, the spherical crystal in the alloy is gradually transformed into a rosette-like crystal, and the average grain size is increased from 21. 02 μm to 58. 13 μm. The content of the second phase β-Mg17Al12 is increased from 18. 55% to 49. 72%, and its uniformity is gradually weakened. When the pouring temperature is low(595 ℃ and 605 ℃), there exist a lot of dimples and a small area of cleavage plane in the tensile fracture. The number of dimples and cleavage steps of the fracture is gradually decreased at a higher pouring temperature. At the pouring temperature of 605 ℃, the tensile strength and elongation reach up to 229. 2 MPa and 3. 16%, respectively.更多还原