A study of processing and parametric optimization of wear-resistant AZ91-TiB2composite fabricated by ultrasonic-assisted stir casting process

Abstract

In the present research, a lightweight and wear-resistant TiB2 reinforced AZ91D Mg metal matrix composite was developed using an ultrasonic-assisted stir casting process for aerospace and automobile applications. Stirrer speed, ultrasonic power, and TiB2 reinforcement concentration were considered the input process parameters, which were optimized with the help of Taguchi's L9 orthogonal array, followed by grey relational analysis to develop the composite with high hardness and wear resistance. Pin-on-disc sliding wear testing was conducted to evaluate the wear resistance of the composites fabricated at different process parameter settings. SEM, EDS, and XRD examined the microstructure, wear mechanisms, elemental composition, and different phases in the developed composites. The microhardness of the specimens was determined using a Vickers microhardness tester. The results revealed that the process parameter setting with a stirrer speed of 400 rpm, 1500 W of ultrasonic power, and 3 wt% of TiB2 reinforcement concentration had the highest grey relational grade, which resulted in the development of a composite material exhibiting the high microhardness and minimum wear. The microstructural investigation revealed that the ultrasonic agitation of the liquid melt resulted in nearly uniform dispersion of the TiB2 reinforcement particulates in the composite. During the sliding wear test, the material removal in the composite specimens occurred due to the adhesion, oxidation, delamination, pull-out of reinforcement particles, and eruption of the Mg alloy matrix.