Ultrasonic Investigation of CMSX-6 Superalloy at Low and High Temperatures

Abstract
The elastic constants C₁₁, C₄₄ and C' have been measured as a function of temperature in a single crystal of CMSX-6 alloy and from these data the bulk, Young's and shear moduli have been deduced, together with the anisotropy factor A and the elastic constant C₁₂. The temperature coefficient of the elastic constants C₁₁ and C₄₄ becomes gradually more negative on approaching the melting point of the alloy. This softening effect is interpreted in terms of a negative contribution to the elastic stiffness of the material arising from thermal vacancies within the disordered γ phase. The anisotropy factor A is found to fall in the typical range of fcc metals and the Cauchy relationship (C₁₂ = C₄₄) appears to be approximately fulfilled, suggesting that the lattice cohesion is associated with a field of central forces.