Investigation of Stresses Induced Due to the Mismatch of the Coefficients of Thermal Expansion of the Matrix and the Strengthening Particle in Aluminum-Based Composites

Abstract

An experimental and theoretical investigation of the strength properties of aluminum alloys strengthened by dispersed nanoparticles, as well as the determination of the significance of various mechanisms responsible for the strengthening of the material, was carried out. Results of experimental investigation demonstrate that the hardening of aluminum alloy A356 by Al2O3 and ScF3 nanoparticles leads to an increase in the yield strength, ultimate tensile strength, and plasticity. Despite the similar size of Al2O3 and ScF3 nanoparticles, the physicomechanical properties of nanoparticles significantly affect the possibility of increasing the mechanical properties of the A356 aluminum alloy. A physicomathematical model of the occurrence of thermal stresses was developed caused by the mismatch of the coefficients of thermal expansion (CTEs) of the matrix and strengthening particles on the basis of the fundamental principles of mechanics of a deformable solid and taking into account the elastic properties of not only the matrix, but also the particle. The forming of thermal stresses induced due to the mismatch of the coefficients of thermal expansion of the matrix and the strengthening particle in aluminum-based composites was investigated. In the case of thermal deformation of dispersion-hardened alloys, when the CTE of the matrix and particles noticeably differ, an additional stress field is created in the vicinity of the strengthening particle. Thermal stresses increase the effective particle size. This phenomenon can significantly affect the result of the assessment of the yield strength. The strengthening caused by thermal mismatch makes the largest contribution to the yield strength improvement. The yield strength increments due to Nardon×Prewo and Orowan mechanisms are much lower.