添加Sc、Zr和退火对Al-Si合金铸态力学性能的影响

使用OM、TEM、SEM、显微硬度和室温拉伸等手段研究了Sc和Zr的复合添加对Al-5.5Si合金铸态的组织和性能的影响，以及在不同温度退火后其性能的变化规律。结果表明，Sc、Zr的添加使Al-5.5Si合金的硬度提高了33%、抗拉强度提高了38%、屈服强度提高了52%、延伸率基本上不变。在Al-5.5Si合金中复合添加Sc、Zr使α-Al的平均晶粒尺寸从203 μm减小到130 μm，在α-Al基体中析出大量的Al₃(Sc_1-xZr_x)纳米粒子(10~15 nm)，并使共晶Si内的层错或微孪晶的密度显著提高。退火温度对铸态合金的性能有较大的影响：在较低温度(低于160℃)退火时合金的硬度呈上升趋势，而在较高温度(高于280℃)退火时合金的硬度呈显著下降趋势。这些结果与二次析出的纳米Si相密切相关。

Effect of Sc and Zr Addition and Annealing Treatment on Mechanical Properties of As-cast Al-Si Alloy

The effect of Sc- and Zr-addition and annealing treatment on the microstructure and properties of as-cast Al-Si alloys were investigated by optical microscopy, transmission electron microscope, scanning electron microscope, microhardness and tensile test. The results show that the addition of Sc and Zr can significantly improve the mechanical properties of the Al-5.5Si alloy, as a consequence the hardness, tensile strength and yield strength of the alloy increased by 33%, 38% and 52% respectively, while the elongation kept basically unchanged. The addition of Sc and Zr in the Al-5.5Si alloy reduced the average grain size of α-Al from 203 μm to 130 μm, and a large amount of Al₃ (Sc_1-xZr_x) nanoparticles (10~15 nm) precipitated in the α-Al matrix which can significantly increase the stacking faults or micro twinning density of eutectic Si. It is noted that the annealing temperature has a greater impact on the properties of the as-cast alloy: the hardness of the alloy had an increasing trend when annealing at lower temperature (below 160℃), and the hardness of the alloy had a decreasing trend when annealing at higher temperature (above 280℃). The significant downward trend can be attributed to the secondary precipitation of nano-Si phase.