Microstructure, High-temperature Tensile and Tribological Behavior of Zn/Cr Composites

To enhance the high-temperature strength and wear resistance of pure zinc, Zn-matrix composites containing 5, 10, and 20 vol% Cr particles were fabricated through melt stirring followed by high pressure die casting (HPDC). Theoretical calculations for Cr particle engulfment during solidification were confirmed by microstructural analysis. Cr particles could effectively refine the grains of pure zinc. As a result, the room temperature (RT) strength increased by adding up to 10 vol% Cr into the zinc matrix. The strengthening effect of Cr particles at 110 °C was even higher than that at RT. It was found that ductile dimple fracture with ripples on the dimple walls was responsible for increased ductility of the zinc and Zn/Cr composite at high temperatures. Results of wear tests for pure zinc showed that increasing the test temperature from RT to 110 °C led to severely fluctuant friction due to the enhanced adhesion. Cr particles stabilized the friction trace of zinc and reduced the mean coefficient of friction, leading to improved wear resistance, especially at high temperatures. At 110 °C, the lowest wear damage was observed for the Zn/20Cr composite, while severe delamination resulted in an excessive mass loss in pure zinc samples.