P+RE变质对过共晶Al-Si合金组织性能的影响

Influence of P and RE Modification on the Microstructure and Properties of Hypereutectic Al-Si Alloy

以过共晶Al-Si合金为研究对象,分析了P+RE变质对合金组织及力学性能的影响,并分析探讨了其强化机制。结果表明,变质后合金组织中粗大块状、条状的初晶Si尺寸明显细化,粗大针状的共晶Si变为纤维状或短杆状,合金的力学性能提高。当P含量为0.08%和RE含量为0.6%时,其室温和高温力学性能最好,室温抗拉强度从未变质的236.2MPa提高到287.6 MPa,高温抗拉强度从142.5 MPa提高到210 MPa,分别提高了22%和47%;伸长率分别提高了57%和42%。初晶Si的变质以AlP异质形核作用机理为主,共晶Si以RE吸附产生孪晶为变质机制。

Influence of P and RE modification on the microstructure and mechanical properties of hypereutectic Al-21Si alloy have been investigated. The results reveal that the coarse bulky and strip primary Si in the alloy can be greatly refined, and eutectic Si is converted from coarse needle into fibre or short bar with modification, which can improve the mechanical properties of the alloy. With 0.08% P and 0.6% RE addition, compared with ones without modification, the tensile strength at room and high temperature of the alloy is increased from 236.2 MPa to 287. 6 MPa, and from 142.5 MPa to 210 MPa, increasing by 22% and 47%, respectively, and the elongation is increased by 56% and 42%, respectively, showing the desirable ambient and high temperature mechanical properties. The modification of primary Si is controlled by heterogeneous nucleation mechanism induced by AlP particles, and the modification of eutectic is resulted form the creation of twin grain from RE absorption. In addition, the strengthening mechanism of the alloy was described.