Sb对A356合金组织和力学性能的影响及变质机理

Effects of Sb on Microstructure and Tensile Properties of A356 Alloy and Analysis of Its Modification Mechanism

研究了Sb含量对A356合金组织和力学性能的影响,并利用热分析、液淬试验对Sb变质机理进行了分析。结果表明,Sb变质A356合金的最佳含量为0.4%,此时共晶Si由粗大的板条状变为细小的纤维状。由于Sb的变质作用,A356合金的力学性能尤其是伸长率得以显著提高,合金的铸态伸长率最高可达11.3%,相比于未变质合金提高了79%。结果表明,Sb能够有效地降低共晶组织的形核温度,提高其形核过冷度,降低共晶组织的形核率。

The effects of Sb additions on the microstructure and tensile properties of A356 alloy were investigated systematically,and thermal analysis and quenching experiments were carried out to explore the modification mechanism of Sb on Al-Si alloys.Microstructure observations show that with 0.4% Sb addition,coarse plate-like eutectic silicon phase can be converted into fibrous structure.Tensile tests show that the mechanical properties（especially the elongation）of A356 alloys are improved greatly.The maximum elongation value reaches 11.3% under as-cast condition,which is 79% higher than that of the unmodified alloy.Thermal analysis and quenching structure observation reveal that the nucleation temperature of eutectic Si phase is continuously decreased with Sb additions,therefore the nucleation undercooling can be increased to decrease nucleation rate of eutectic Si phase.