热冷组合铸型(HCCM)连铸5A02铝合金管坯微观组织和力学性能

Microstructure and mechanical properties of 5A02 aluminum alloy tube billet fabricated by HCCM continuously casting

热冷组合铸型(Heating-cooling combined mold,HCCM)水平连铸是一种制备高精度管坯的短流程新技术。本文采用HCCM水平连铸成功制备出d 70 mm×6 mm规格的5A02铝合金管坯,研究了微观组织对管坯力学性能的影响。结果表明:不同的连铸工艺导致形成了三种不同的铸态组织,分别为粗大等轴晶组织、粗大柱状晶组织和细长柱状晶组织。更较大的连铸速度和温度梯度导致形成的细长柱状晶组织表现出优异的力学性能,其室温抗拉强度为198 MPa,断后伸长率为26.3%。在细长柱状晶组织中,弥散分布的细小第二相和沿轴向的细长晶粒,以及Mg元素在α(Al)基体中的均匀分布使得管坯力学性能明显提高。

Heating-cooling combined mold(HCCM)horizontal continuous casting was a new compact process technology for preparing tube billets with high precision.In this work,5A02 aluminum alloy tube billets with 70 mm in diameter and 6 mm in wall thickness were fabricated by HCCM horizontal continuous casting,and the effect of microstructure on mechanical properties was investigated.The results show that the different HCCM processes result in three different microstructures,respectively coarse equiaxed grains,coarse columnar grains and slender columnar grains.The slender columnar grain introduced by the higher casting speed and temperature gradient presents the more excellent mechanical properties,including ultimate strength of 198MPa and elongation of 26.3%.The grain size,second phase size and the distribution of Mg element are main factors for mechanical properties.For the slender columnar grain,diffusion of fine second phase and the uniform distribution of Mg element inα(Al)matrix improve the mechanical properties of HCCM casted tube billets.