镍对Al-Zn-Mg-Cu-RE超高强铝合金组织和硬度的影响

Effects of Ni on Hardness and Microstructure of Ultra High Strength Aluminum Alloy Al-Zn-Mg-Cu-RE

采用金相观察、布氏硬度测试、X-射线衍射、扫描电镜结合能谱分析等手段,研究了以稀土为晶粒细化剂的Al-Zn-Mg-Cu-Re超高强铝合金中添加合金元素镍后其组织和硬度的变化。结果表明,合金在铸态下的硬度大体上随镍含量的升高而升高,经T5热处理后在镍含量为0.25%时硬度达到最大值(138 HB)。通过检测发现镍在该合金中除中和铁生成Al9FeNi相外,还生成了强化相Al7Cu4Ni,在时效过程中起沉淀硬化作用。但过多的镍反而对该铝合金性能产生不良影响,初步认为镍在Al-Zn-Mg-Cu系铝合金中的加入量应控制在0.25%左右。

The microstructure and hardness of RE-grain-fined Al-Zn-Mg-Cu Aluminum alloy were researched and analyzed by means of optical microscope,hardness test,XRD ,SEM after nickel was added in the alloy. The results show that the alloy＇s hardness as-cast increases with the increase of nickel content, and the maximum hardness after T5 heat treatment is 138HB when nickel content is 0.25%. Phase AlgFeNi and Al7Cu4Ni are found in the grain boundaries, which acts on precipitation hardening in aging process.The nickel content in Al-Zn-Mg-Cu aluminum alloy should be limited to around 0.25% because more Ni has the worse effect on the property of the alloy.