Enhanced mechanical and tribological properties of ultrasonically assisted stir-cast AA7075 metal matrix composites in challenging corrosive environments

Abstract

Aluminum-based metal matrix composites (AMMCs) find extensive applications in aerospace, automotive, defence and various sectors on account of remarkable mechanical properties, lightweight nature, and excellent dimensional stability. In this research, AA7075 matrix material was reinforced with tungsten carbide ceramic particles with various 0, 5, 10, 15 and 20 weight percentages (wt.%) with the use of Ultrasonic assisted stir casing setup. The stir casted AA7075 MMCs were subjected to XRD, SEM, and density test to analyse the presence of elements, microstructure and density. The tensile, micro hardness, and wear test were performed on AL7075 based MMCs after conducting NaCl based spray test at the condition of spray pressure of 1.2 kg/cm2, spray duration of 120 hours and PH value of 8.2 to determine the micro hardness, Ultimate Tensile Strength and wear resistance. The XRD test confirmed the presence of secondary phases such as Al2Cu, W2C, and MgZn2 with Al and WC phases. The SEM test confirmed the uniform dispersion and no more cluster formation upto 15wt.% WC addition and agglomeration of WC was occurred in the addition of 20wt.% of WC.. The enhancing of wt.% of WC enhanced the Micro hardness, UTS, wear and corrosion resistance up to 15 wt. % addition and decreases by the 20 wt.% WC addition. The higher tensile strength 312 MPa was obtained from AA7075/15wt.%WC composite. The lower wear rate 0.11 mg/m was obtained from AA7075/15wt.%WC at 1000 m sliding distance with 1.2 m/s sliding velocity. The improved mechanical and tribological properties were mainly depended on strengthening mechanisms such as load transfer mechanism and dislocation strengthening mechanism.