Effect of Rare Earth Upon As-Cast Microstructure and High Temperature Performance of ZA40 Alloy
In testing comparison, this study is made on the modification effect of 0.05 wt.% La-rich rare earth (RE) upon as-cast microstructure, mechanical properties of materials at high temperatures (100, 150, 200°C) and wear resistance under different temperatures (100and 200°C) of ZA40 alloy containing Si. The addition of RE shows that it can not only effectively refine Al-rich and Cu-rich phase, but also reduce the amount of needle-like eutectic silicon, and then make the size of massive primary silicon phase smaller. Thus, there are the improvement of strength, ductility and wear resistance of materials at high temperature. The analyses are also conducted on the mechanism of underlying RE elements.
Hot deformation and processing map of ZA27 alloy
The hot deformation behavior of ZA27 alloy were investigated by compressive tests on Gleeble-1500 thermal-mechanical simulating tester in the temperatures range of 200-350 ℃,strain rate range of 0.01-5 s-1 and engineering strain of 60%.Based on Murty criterion,the processing map for the ZA27 alloy was obtained.The results show that the flow stress decreases with the increase of temperature,while increases with the increase of strain rate.The flow instability regimes appear at two different regimes: at the temperature of 200-210 ℃and the strain of 0.01-0.1 s-1,as well as at the temperature of 250-350 ℃ and the strain rate of 1-5 s-1.The dynamic recrystallization is the main reason for flow softening and stable flow.The hot deformation of ZA27 alloy can be carried out safely in the region with a strain rate of 0.1-1 s-1 and temperature range of 250-350 ℃.
The Lunar Rocks
Book on lunar rocks covering pre-Apollo lunar scientific knowledge, Apollo and future lunar mission planning, lunar mineralogy, petrology and geochemistry, etc