Product Code: ICA11_1103

Formation of Metal Matrix Composites and Intermetallic Phases on Aluminum AA1200 During Laser Alloying
Authors:
Luyolo Mabhali, CSIR National Laser Centre, University of Witwatersand; Pretoria Republic of South Africa
Sisa Pityana, CSIR National Laser Centre, Tshwane University of Technology; Pretoria Republic of South Africa
Natasha Sacks, University of the Witwatersrand; Johannesburg Republic of South Africa
Presented at ICALEO 2011

Laser surface alloying of aluminium AA 1200 was performed with a 4.4 kW Rofin Sinar Nd:YAG laser to improve its hardness and wear resistance. Alloying was carried out by depositing Ni, Ti and SiC powders with different weight ratios on the aluminium substrate at 10mm/s laser scanning speed. Surfaces reinforced with metal matrix composites and intermetallic phases were achieved after laser alloying. The phases observed in the microstructure depend on the composition of the alloying powder mixture. The reactions of Al with Ni resulted in the in situ formation of Al3Ni and Al3Ni2 intermetallic phases while Ti reacted with Al to form an Al3Ti intermetallic phase. Some of the SiC particles dissociated and reacted with either Al or Ti to form Al4C3, Al4SiC4, TiC or Ti3SiC2 phases. Si reacted with Ti to form a Ti5Si3 phase. Surface hardness increased with increasing Ni content in the alloying powder mixture and a maximum of 13 times that of aluminium was achieved when alloying with 80wt%Ni + 15wt%Ti + 5wt%SiC. The increase in hardness was attributed to the intermetallic phase formed in the alloyed surface especially the Al3Ni2 phase.