Surface Improvement by Overlapping in Multipass FSP

Abstract

Friction stir processing (FSP) is an emerging metal-working technique based on the same fundaments as friction stir welding that allows local modification and control of microstructures, for the purpose of improving surface or in-volume mechanical properties. This paper aims to explore several applications of the FSP technology for surface improvement either by multipass FSP or surface reinforcement with silicon carbide particles. An AA5083-H111 alloy 8 mm thick was tested. Structural and mechanical differences were observed when overlapping by the advancing side (AS) direction or by the retreating side (RS) one. Hardness within the processed layer increased by 8.5 % and was seen to be approximately constant between passes. Toughness under bending was improved by 18 %. The production of particle-reinforced metal matrix composite materials (MMC) was investigated, as the severe plastic deformation inherent to the process promoted the dispersion of 12.5 μm median size SiC particles, resulting in a severe superficial hardness increase.