高强可焊7A62铝合金的成分设计与跨尺度相强化作用

基于7A62铝合金的成分设计,研究Zn含量和Zn/Mg质量比对Al-Zn-Mg合金强度的影响。采用透射电镜(TEM和HREM)详细地研究7A62铝合金峰值时效的析出相,从多个晶体学方向观察了强化析出相的形貌及其与基体的关系。结果表明:Zn/Mg质量比为2~3、Zn含量增加至6.84%(质量分数)时,7A62合金的强度明显增加。峰值时效后,7A62合金基体形成了体积分数约60%、尺寸小于10 nm的沉淀强化相和体积分数约10%、尺寸为100~200 nm的弥散强化相。基体主要强化析出相是高密度均匀分布的η′相,与基体呈现半共格和晶体取向关系,形成较高晶格错配度;跨尺度位错缠结的弥散强化相是由Al、Zn、Mg、Mn元素组成的平衡相。7A62合金的化学成分和微结构特征使其成为高强可焊的铝合金。

Composition design and trans-scale precipitates strengthening of high-strength weldable 7A62 Al-alloy

The effects of Zn content and mass ratio of Zn and Mg on the strength of the Al-Zn-Mg alloys were investigated in order to develop a high-strength weldable 7A62 Al-alloy.The hardening precipitates of the 7A62 Al-alloy treated by peak aging were investigated in detail by transmission electron microscopy(TEM and HREM).The results show that the strength of 7A62 alloy with m(Zn)/m(Mg)of 2?3 and Zn content of 6.84%(mass fraction)increases obviously.After peak ageing,this alloy has the precipitates with volume fraction of 60% and the size<10 nm,and has the dispersed particles with volume fraction of 10% and the size of 100?200 nm.The high density uniformity η′particles are the main strengthening precipitates in the matrix,and are semi-coherent or orientation relationships with the Al matrix,and form the high lattice mismatch.The trans-scale dispersed particles tangled by the dislocation are composed of Al,Zn,Mg,Mn elements.The new 7A62 aluminum alloy can become the high strength of weldable Al-Zn-Mg alloys due to the chemical composition and microstructure characteristics.