Fabrication and optimization of AA7075- 7%SiC surface composites using RSM technique via friction stir processing

Abstract

Alteration of surface properties of low-strength alloys using friction stir processing (FSP) has been under development for the last three decades. Using FSP, surface composites of metal can be obtained with modified surface properties by inserting reinforcement particles (RPs). Despite having a good strength-to-weight ratio, Al alloys have limited uses due to their weaker surface properties. In this work, AA7075 alloy was used as the matrix to enhance its surface properties by reinforcing SiC particles (07 % by volume) using FSP. The tool speeds, i.e., traverse and rotational speed and no. of passes of the FSP were used as the independent input parameters or factors, and these factors were varied in three levels. The remaining parameters, like tool geometry, tilt angle, axial force, quantity of RPs etc., were kept constant. The selection of independent factors, their working limits and the value of other constant parameters were fixed by conducting trial experiments and examining the latest literature. Tensile strength and microhardness of the fabricated composites were used as responses, and the effects of the three factors on these responses were studied with a central composite design (20 runs) of RSM (response surface methodology). Analysis of variance (ANOVA) developed mathematical equations for finding the responses and suggested that the designed models were significant for both the responses. The maximum microhardness of 155 HV and the maximum strength of 617 MPa were obtained for the run 1 (rotational speed- 730 rpm, traverse speed- 65 mm/min, number of passes- 3).

Keywords

• FSP
• Surface metal matrix composite (SMMC)
• Microhardness
• UTS