Constitutive modeling of flow stress during hot deformation of Sn-Al-Zn-Cu-Mg multi-principal-element alloy

Reports on the constitutive modeling during elevated temperature deformation of multi-principal-element alloys (MPEA) are scant and the correlation of constitutive relationships with the established creep theories remained to be unraveled. In response, in the present work, the high-temperature constitutive behavior of a new MPEA containing Sn, Zn, Cu, Al, and Mg was studied based on the hot compression tests. In the microstructure of the alloy, beta-Sn as the matrix phase along with the Zn, alpha-Al, Mg2Sn, and Al4.2Cu3.2Zn0.7 phases were observed. The deformation activation energy was found to be near the lattice self-diffusion activation energy of beta-Sn (108.9 kJ/mol). However, basic constitutive analysis resulted in the stress exponents of similar to 15.5, which was related to the interference of other phases with the hot deformation mechanism in this alloy. Via consideration of a threshold stress (sigma(th)), and proposing a unique method for calculation of sigma(th), the stress exponent of similar to 5 was obtained. Based on creep theories, the glide and climb of dislocations in the climb-controlled regime was found to be responsible for hot deformation of this alloy. Accordingly, a reliable and physically-based constitutive equation was proposed for prediction of hot flow stress.