Effect of Al Content on Microstructure and Stress Rupture Properties of Nickel Based Single Crystal Superalloy
The effects of Al content on the microstructure of as-cast and heat treatment specimens were investigated.The stress rupture of the alloy at high temperature was measured and the microstructure of stress rupture specimens was observed by SEM,EDS,and XRD.The results show that the as-cast microstructure of the alloy is composed of coarsening γ',fine γ' and γ.With the increase of Al content,the more coarsening γ' appears in the alloy and cannot be dissolved into γ matrix completely during solid solution heat-treating.The observation of microstructure indicates that the micro-cracks occur mainly at the coarsening γ'/γ interface during stress rupturing measuring and extends along γ'/γ interface,all these are harmful to the high temperature properties of the alloy.