Herein, the cause and change of micropores, the cause of the incipient melting structures, and the increase of the maximum homogenization temperature of a nickel-based single crystal (SC) superalloy during homogenization are researched. The results show that the micropores are generated because of unbalanced diffusion during homogenization and form incipient melting structures at high temperature because of the lack of rhenium (Re) and tungsten (W). With the diffusion of Re and W, the porosity is decreased from 0.169% to 0.06% and cannot be further decreased because of the existence of shrinkage pores, the maximum homogenization temperature is increased to more than 1350 C, and the rupture life at 1100 C/150 MPa is improved to 217 h.
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.
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