Preparation of in-situ ZrB2/A356 composites and high-temperature tribological studies

Abstract

The ZrB2/A356 composite material was prepared by using chemical in situ reaction technology. The high-temperature friction and wear test of ZrB2/A356 aluminum matrix composites was carried out. The friction and wear test temperatures were normal temperatures, 50 °C, 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C. XRD, TEM, SEM, and XPS were used to analyze the microstructure, phase and the formation of surface compounds of the composites under different wear temperatures. The results show that the composite phase is composed of ZrB2 and ɑ-Al, and there is a small amount of Al-Si eutectic phase; ZrB2 particles are small, hexagonal nearly elliptical, flocculent and well bonded to the matrix; Combined with the stress-strain curve and tensile fracture morphology analysis, the composite material is a ductile fracture, and the plasticity of the A356 alloy is higher than that of the composite material; The wear properties of composites are susceptible to temperature changes, and the wear rate is small below 200 °C. The wear mechanism is mainly oxidative wear and abrasive wear. When the temperature reaches above 250 °C, the wear rate begins to rise sharply, and a large number of plastic deformation traces and wear debris appear on the surface of the wear spot, and the surface of the wear debris adheres to the protrusions. The primary wear mechanism is adhesive wear. In the stages of oxidative wear, and abrasive wear, although the friction coefficient changes, it is stable. But in the adhesive wear stage, the friction coefficient becomes very unstable and a sharp peak appears. XPS analysis showed that the compounds formed in the wear scar were mainly Al2O3.