The effects of Sm and Zr amount on the properties of Mg-Cu-Sm-Zr alloys were systematically investigated. The results showed that the Mg99Cu alloy consist of-Mg matrix and Mg2Cu phase. After the addition of Sm and Zr, it was confirmed that Sm and Zr change the structure and distribution of Mg2Cu phase. In the meantime, the CuZr2 and CuSm phases which make a major contribution to mechanical properties were observed in the Mg-Cu-Sm-Zr alloys. The addition of Sm and Zr can also greatly refine the grains. The strength continuously increased due to the increase of Sm and Zr content. The elongation first increased within the range of 0-1.5%Sm 0-0.9%Zr, and the decreased. The alloys with 0.5wt%Sm and 1.9wt%Zr had the best combination of mechanical properties.
Small amounts of various alloying elements were added to a high strength Al-Zn-Mg-Cu alloy and their effects on the microstructure, mechanical properties, and casting characteristics were investigated. Silicon additions with or without extra Mg to the Al-Zn-Mg-Cu alloy could enhance the castability such as fluidity, feedability, and hot tearing resistance significantly while maintaining a high strength. However, in these alloys containing silicon the compositional adjustment was necessary to prevent the Mg2Si phase formation from degrading the precipitation of MgZn2 phase that is responsible for the high strength. Zr addition to the base alloy was also observed to improve the feedability without deteriorating the tensile strength.
Development and Estimate of Extruded High Strength Al-Zn-Mg-La System Alloys with High Stress Corrosion Cracking Resistance. III. Effects of Zr Addition on Microstructures and Mechanical Properties of Extruded Al-Zn-Mg-La System Alloys with High Stress Corrosion Cracking Resistance.