Effects of Nd content on thermal expansion behavior of Mg-Nd alloys

The effects of annealing temperature, thermal cycle times, precipitates, and Nd content on the thermal expansion behavior of as-extruded Mg-xNd (x=2, 4) binary alloys were investigated. It demonstrated that the coefficient of thermal expansion (CTE) of alloys decreased with the increasing of Nd content. The annealing treatment eliminated partial residual stress inside the alloy, which led to the CTEs of annealed samples higher than that of the unannealed samples at low temperature. However, it was opposite at high temperature after multiple thermal cycles due to the amount of Mg41Nd5 phase increased after annealing treatment. The results of the calculated cumulative residual strain of the Mg-Nd alloys with thermal cycling indicated that the alloys annealed at 325 ℃ has the best thermal stability. The rule of mixtures (ROM) and Kerner model were proposed to predict the CTEs of Mg-Nd alloys. It was found that the prediction of the Kerner model was agrees well with the experimental data of 1st thermal cycle of samples without internal stress.