Formation of metal matrix composites and intermetallic phases on aluminium AA1200 during laser alloying

Abstract

Laser surface alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve it 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 reinfrorced with ceramics 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. Some of the SiC particles dissociated and reacted with wither 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 phases formed in the alloyed surface especially the Al3Ni2 phase.Laser surface alloying of aluminium AA1200 was performed with a 4.4kW Rofin Sinar Nd:YAG laser to improve it 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 reinfrorced with ceramics 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. Some of the SiC particles dissociated and reacted with wither 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 phases formed in th...