Effect of composition of welding wire on microstructure and mechanical properties of weld metal in SiC particle reinforced 6061Al matrix composite

The SiC_p/6061 Al alloy composite was welded by usingM1G and pulsed-MIG welding with Al-Si or Al-Mg filler metal.The micro-structure of weld metal was investigated with OM and TEM,and the properties of weld metal were investigated with MTS-810 testing system.The results showed that when welding with Al-Mg filler metal,serious reaction between Al matrix and SiC particles occurred in the molten pool,and a quantity of large-size acicular Al₄C₃ formed in the weld metal.With Al-Si filler metal used,the interfacial reaction between Al matrix and SiC particles was alleviated remarkable,only a little small-size acicular Al₄C₃ was tound in the MIG weld,while no acicular Al₄C₃ phase was found in the pulsed-MIG weld.It was also found that Si in welding wire can prevent from the formation of hot-crack in weld.The mechanical testing resuits showed that tensile strengths and elongation of welds deposited with Al-Si filler metal was higher than those of welds deposited with of Al-Mg filler metal.With the same welding wire used,the tensile strength and elongation of welds deposited with pulsed-MIG was high than those of welds deposited with MIG.