In situ synthesis of aluminium matrix surface composites by friction stirprocessing

Al matrix surface composite layers reinforced with in situ synthesized Al3Ni and TiC compounds were produced on Al 1050 sheets by friction stir processing (FSP). Effects of traverse speed, rotational speed and heat treatment on the microstructure and hardness of specimens were studied. FSP induced reaction between mechanically alloyed (MA) Ni-Ti-C powders and aluminium matrix was investigated. Microstructural evaluation of the samples was conducted by optical microscopy (OM) and scanning electron microscopy (SEM) of the cross-sections of surface composite layers fabricated by FSP. X-ray diffractometery (XRD) was used to study the structural evolutions. Hardness profiles were obtained from microhardness measurements across the cross-sections of FSPed samples. Improved distribution of Ni-Ti-C particles and smoother hardness profile observed at 1400 rpm and 40 mm min-1 rotational and traverse speeds, respectively. Defect-free in situ composites containing Al3Ni and TiC reinforcements were successfully produced after two passes of FSP at optimum speed. Surface composite layers obtained from FSP showedincreased hardness up to about 60 VHN.

Keywords:

Al matrix composites , In situ synthesis , Friction stir processing , Microstructure