Study on the Thermal Expansion Behavior of Mg-3RE Alloys and Mg-3Y/SiCp Composites

The high coefficient of thermal expansion (CTE) of magnesium alloys leads to poor thermal dimensional stability and limits its application in the electronic field. This work focused on understanding the effect of rare earth (RE) on the thermal expansion behavior of Mg and attempted to tailor the CTE with SiC particulates. Composites were manufactured by gravity casting with ultrasonic dispersion treatment. The effect of 3 wt.% RE (Sm, Nd, Gd, Y) on the microstructure and thermal expansion behavior of the Mg alloys was explored. Adding RE can lead to the formation of RE-containing second phases and marginally decreased the CTE of magnesium. The CTEs of Mg-3Sm, Mg-3Nd, Mg-3Gd and Mg-3Y alloys were 27.3 × 10 −6 /°C, 27.0 × 10 −6 /°C, 27.2 × 10 −6 /°C and 27.8 × 10 −6 /°C, respectively. The influence of SiC p on the thermal expansion behavior of Mg-3Y was also investigated. The SiC p promoted the precipitation of Mg 24 Y 5 phase in the extruded Mg-3Y/SiC p composites and significantly reduced the CTE. The CTEs of Mg/3SiC, Mg-3Y/1SiC, Mg-3Y/3SiC and Mg-3Y/5SiC were 27.4 × 10 −6 /°C, 26.8 × 10 −6 /°C, 26.6 × 10 −6 /°C and 23.3 × 10 −6 /°C, respectively. Rule of mixture, the Turner model and the Kerner model were utilized to predict the CTE of the Mg-3Y/ x SiC p ( x = 1, 3, 5) composites. The predictions of the Kerner model show a better correlation with the experimental results.