Microstructural characterization and properties of in situ Al-Al ₃ Ni/TiC hybrid composite fabricated by friction stir processing using reactive powder

Microstructural evolutions during in-situ fabrication of Al-Al ₃ Ni/TiC hybrid composite by friction stir processing (FSP) of AA1050 alloy with inserting reactive powder were investigated. Reactive powder was prepared by double step mechanical alloying (MA) of elemental Ni, Ti and C powders for a total duration of 20 h. Mechanical activation of pre-milled powders resulted in the in situ synthesis of Al ₃ Ni/TiC particles in Al matrix during FSP. By increasing the number of FSP passes, a more uniform distribution of reinforcing particles along with higher degree of in situ reaction could be achieved. Complete reaction of MAed powders was attained after 6 FSP passes which resulted in the formation of Al ₃ Ni and TiC reinforcing particles in Al matrix. In situ composite obtained from with 6 FSP passes exhibited phase stability during high temperature exposure. Al-Al ₃ Ni/TiC hybrid composite showed superior hardness of 70 HV and ultimate tensile strength of 179 MPa compared to those of AA1050 (25 HV, 84 MPa) and FSPed AA1050 without powder addition (30 HV, 90 MPa).