Friction stir selective alloying of different Al% particulate reinforced to AZ31 Mg for enhanced mechanical and metallurgical properties

Abstract

An attempt was made to selectively alloying Mg base matrix with 3%, 6% and 9% volume of Al particulates respectively, using friction stir selective alloying (FSSA). The objective of this investigation is to enhancing the mechanical and metallurgical properties of AZ31 Mg using solid state alloying process. Tensile properties revealed an enhanced strength of 249.4 MPa at 6% Al alloying sample and which is 95% strength of base material. The fractography detects a ductile fracture consisting of dimples, cup and cone shape counterparts with the fracture initiation area and propagation direction. Hardness indentation depicts improved micro-hardness properties and 185% of base alloy in case of 6% alloying due to presence of favorable reinforcing intermetallic particles in the stir area. The hardness relatively varies corresponding to % of Al alloying element at the stir zone. The 6% alloying sample gives best mechanical properties compared to the 3% and 9% alloying. Line scan/mapping technique detects the uniform distribution of the alloying elements. The EDX analysis spot formation of different intermetallic phases, namely AlMg, Al12Mg17 and Mg2Al3. The XRD analysis also informs the intermetallic phase formation and well agrees with EDX analysis. Alloying at different Al% to the Mg base matrix helps in microstructural modification, including uniform dispersion of the alloying element, finer grain and minimum assembled particles at the stir zone leads to improved metallurgical and mechanical properties. The stirred zone consists of metal matrix solid solution of martensitic structure and relatively finer grain compared to base alloy.