Dry sliding tribological behavior of ultrasonic stir cast AZ31-B4C composites

Abstract

The current study deals with the tribological characterization of AZ31-B4C composites synthesized through ultrasonic vibration associated stir casting route. B4C particles with varying weight percentage (0.5–2.0 wt. %) are reinforced in magnesium alloy to produce the composites. Optical microscope (OM), scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDX) are utilized to characterize AZ31 alloy and composites so fabricated. Characterization illustrates the presence of boron carbide (B4C) and its effect on the grain refinement of composites. Micro hardness of composites is measured through Vickers's micro hardness tester. AZ31-B4C composites exhibit better hardness compared to AZ31 magnesium alloy. Micro hardness of AZ31- 2B4C composite is increased by about 49% compared to AZ31 alloy. Dry sliding tribological behavior is investigated using a pin-on-disc tribo-tester. Wear behavior of AZ31 alloy and AZ31-B4C composites is investigated under applied load of 10–40N and sliding speed of 0.1 to 0.4 m/s. The composites show better wear and friction behavior. Wear resistance of AZ31-2B4C composite is improved around 30% compared to base alloy when tested at 0.2 m/s sliding speed and 40N load. SEM and EDX analysis of worn-out surfaces reveal the wear mechanisms based on different sliding parameters. The wear morphology of pin samples reveals the presence of abrasion, oxidation, adhesion and delamination mechanism either occurring individually or in mixed mode on the pin surface.