Mn含量对高饱和度Al-8Zn-1.8Mg-1.4Cu合金强度的影响

通过透射电镜(TEM与HRTEM)、室温拉伸测试、JMatPro模拟等手段,研究了0.4%与0.8%的Mn对高饱和度Al-8Zn-1.8Mg-1.4Cu合金锻件抗拉强度、屈服强度的影响。结果表明,当合金中含有0.4%与0.8%的Mn时,合金抗拉强度分别达到545、553MPa,较基体合金分别提高7.9%和9.5%,屈服强度分别达到448、469MPa,较基体合金分别提高16.3%和17.4%;向Al-8Zn-1.8Mg-1.4Cu合金中添加Mn元素,经过固溶时效热处理后合金中形成Al6Mn析出相,Al6Mn析出相以棒条状存在于晶粒内外,其数量随Mn含量提高而增多;固溶时效后,Al6Mn析出相与铝基体以非共格形式存在,以弥散强化方式提高合金强度;另外,Mn原子会置换铝基体中的Al原子,导致面心立方铝基体晶格发生膨胀、晶格常数变大,产生晶格畸变,实现固溶强化。

Effects of Mn Content on Strength of the High Saturation Al-8Zn-1.8Mg-1.4Cu Alloy

The effects of 0.4%and 0.8%Mn element content on the tensile strength and yield strength of highsaturation Al-8Zn-1.8Mg-1.4Cu alloy forgings were investigated by means of transmission electron microscopy,high resolution transmission electron microscopy,room temperature tensile testing and JMatPro software.The results reveal that with 0.4%and 0.8%Mn addition,the tensile strength of the Al-8Zn-1.8Mg-1.4Cu alloy reaches 545 MPa and 553 MPa,respectively,which is increased by 7.9%and 9.5%compared with that of the matrix alloy,and the yield strength reaches 448 MPa and 469 MPa,which is increased by 16.3%and 17.4%compared with that of the matrix alloy.The Al6Mn precipitate phase can be formed in the solution heat treatment alloy with the Mn addition after solid solution and ageing treatment,where the Al6Mn precipitate phase exists in the shape of a rod inside and outside the grains,and the amounts are increased with the increase of the Mn content.In addition,the precipitated phase of Al6Mn exists in a non-coherent form with the aluminum matrix after solution heat treatment,and the strength of the alloy is enhanced by dispersion of Al6Mn phases.The Mn atom can replace the Al atom in the aluminum matrix,resulting in the lattice expansion of the face-centered cubic aluminum matrix and the lattice constant increase,so leading to lattice distortion and solid solution strengthening.