Effect of heat treatment on microstructure and wear behavior of in-situ formed Al 3003/Al3Zr+ Al3Ti composite fabricated via friction stir processing

In this article, in-situ formed hybrid surface composite of Al 3003/Al3Zr + Al3Ti was fabricated by friction stir processing (FSP). A rolled Al 3003-H14 aluminum alloy sheet and zirconium and titanium metal powders were used as reinforcements and six passes of FSP were applied. Then, FSPed samples were subjected to annealing heat treatment at 500 ºC for 4 hours. Wear behavior and the hardness of the base metal as well as FSPed samples before and after annealing was measured. Microstructural observation was performed using optical (OM) and scanning electron microscope (SEM), and phase formation was identified with X-Ray diffraction (XRD). Microstructural examination revealed that applying the FSP, resulted in fine and equiaxed grains with more uniform distribution of reinforcing particles. It was also observed that chemical reaction occurred at the interface between the aluminum matrix and the metallic powders, to form aluminides of Al3Zr and Al3Ti. The post annealing heat treatment activated these solid state reactions and more aluminides were formed. It was also found that, the maximum hardness and wear resistance were obtained by the FSPed and annealed hybrid composite sample.