Development of AA6061/316 stainless steel surface composites via friction stir processing: Effect of tool rotational speed

Abstract

Metallic and alloy particles are recognized as alternatives to ceramic reinforcements to improve the overall characteristics of Al metal matrix composites. The present study aimed to investigate the friction stir processing/manufacturing of the 316 stainless steel particles reinforced AA6061 Al matrix composites by varying the tool rotational speeds. The microstructure, tensile, hardness, wear, corrosion behavior, and shear punching tests of the composites were studied. The results showed that the friction stir processing route produced no particle-matrix reaction in the composite and dislocation entanglements were formed close to the inherent 316 stainless steel particles within the Al matrix. The improved mechanical action of the tool aided particle fragmentation as the average 316 stainless steel particle sizes decreased from 41.88 to 26.89 μm. As a result of the dynamic recrystallization and particle-assisted pinning effects, the mean grain sizes of the composite decreased from 7.48 to 4.31 μm when the tool rotational speed was raised. An increment in the tool rotational speed (800–1200 rpm) triggered a rise in the maximum shear force (1198–1562 N), tensile strength (200.09–279.98 MPa), and maximum hardness value (121–139 HV) of the composite while a favorable decrease in the composite's wear rate (0.63–0.20 mg/m) and the friction coefficient (0.38 ± 0.01–0.21 ± 0.01) ensued. The composite's improvement is attributable to the homogeneous spread of dislocation.