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研究了Nd含量对活塞用Al-Si合金的组织演变和力学性能的影响。通过金相显微镜(OM)、扫描电子显微镜(SEM)分析了Nd对该合金凝固过程中析出相的形貌和分布的影响。并对其力学性能进行了测试研究。结果表明:当Nd含量≤0.3%时,随着Nd含量的增加,α-Al基体得以细化。在Nd含量0.3%时,初生硅的等积圆直径较未添加Nd时减小了73%,当Nd含量增加至0.8%及以上时,合金中出现了富稀土相,其力学性能显著降低。Nd含量为0.3%的Al-Si合金的350℃抗拉强度较未添加Nd的Al-Si合金提高了29.8%。由于Nd元素聚集在AlCuNi相周围,造成了成分过冷,抑制了AlCuNi相的长大,AlCuNi相由粗大的骨骼状转变为细小的棒状。
The effect of Nd content on microstructure and mechanical properties of Al-Si alloy for piston was investigated. The influence of Nd on the morphology and distribution of the precipitates during the solidification process was analyzed by OM and SEM. And its mechanical properties were tested. The results show that when the content of Nd is less than 0.3%, the α-Al matrix is refined with the increase of Nd content. When the content of Nd is 0.3%, the equivalent circle diameter of primary silicon is reduced by 73% compared with that without Nd addition. When the content of Nd is increased to 0.8% or more, the rare earth rich phase appears and the mechanical properties of the alloy are remarkably reduced. The 350 ℃ tensile strength of Al-Si alloy with Nd content of 0.3% is 29.8% higher than that of Al-Si alloy without Nd addition. Due to the accumulation of Nd elements around the AlCuNi phase, the composition is undercooled and the AlCuNi phase is inhibited from growing. The AlCuNi phase changes from a coarse bone to a small rod.