Development and characterization studies on magnesium alloy (RZ 5) surface metal matrix composites through friction stir processing

Abstract

Surface metal matrix composite is produced on the as cast Magnesium Rare Earth alloy – RZ 5 by single pass friction stir processing using various micro/nano sized reinforcement particles namely Boron Carbide (B4C), Multi Walled Carbon Nano Tubes (MWCNTs), and a mixture of ZrO2 + Al2O3 particles. Fine grained metal matrix composites having the grain size ranging 0.8 µm to 1.87 µm are achieved. Grain boundary pinning by the reinforcement particles has resulted in the transformation of coarse grained (∼81 µm) base material into fine grained (<1 µm) metal matrix composite. Finer grain structure and the presence of reinforcements at the stir zone have resulted in increased and improved mechanical properties of the developed composites. Microhardness ranging between 125 HV and 403 HV is achieved. Uni-axial Tensile Testing of the developed composites exhibited improvement in tensile strength. Metal matrix composites developed using various reinforcements exhibited an increase in strength ranges between 250 MPa and 320 MPa. Keywords: Friction stir processing, Magnesium Rare Earth alloy – RZ 5, B4C, MWCNT, ZrO2+Al2O3, Microhardness, Grain boundary pinning