Effect of La Addition on the Microstructures and Mechanical Properties of 7075 Aluminum Alloy

Proper homogenization, solution and aging technologies of the Al-Zn-Mg-Cu-La alloy were studied in this paper. After 46 /24h homogenization, the dendrite segregation and non-equilibrium phase of the alloy were basically eliminated. At the early stage of aging, the hardness and strength of the alloy increase rapidly, the peak hardness and strength are achieved after 120 aging for 13 h, then maintained at a high level for a long time. The results indicate that the mechanical properties of the A1-Zn-Mg-Cu alloy can be obviously improved by La addition. When the La content is 0.12 wt%，the strength increment is the largest, the tensile strength can be increased by 6.4%, while the elongation is increased by 26%．