Evolution of the microstructure, texture and thermal conductivity of as-extruded ZM60 magnesium alloy in pre-compression

Abstract

A systematic study on the influence of pre-compression on the microstructure evolution, texture and thermal conductivity of as-extruded ZM60 alloy was performed. The results indicated that the lenticular shaped {10–12} extension twins were generated during the pre-compression along ED (extrusion direction), resulting in the formation of c-axis//ED texture component and the volume fraction of {10–12} extension twins increased as the pre-compression strains increased from zero to 8.3%. Such microstructure evolution led to a crystal orientation deflection of alloy, and the probability of electrons and phonons being scattered by defects in this direction became much lower, and the mean free path of electrons and phonons in this direction was improved, leading to an increase in the thermal conductivity of alloy. Upon further increase of pre-compression strain, a small amount of the {10–12}-{10–11} contraction twins and {10–12}-{10–11}-{10–12} ternary twins were observed, which introduced a reorientation of the c-axis of grains by ∼56° and ∼38°, respectively. So the mean free path of electrons and phonons decreased, due to the decrease of volume fraction of grains with c-axis parallel to ED, and the thermal conductivity of the alloy decreased. Therefore, the thermal conductivity of alloy first increased and then decreased with the increase of pre-compression strain, and the alloy with pre-compression strain of 8.3% showed the best thermal conductivity of 108.8 W/(m·K).