Investigation of mechanical properties of welding zone at CO2 Laser welded aluminium matrix composites

The aim of this study was the production of SiC particle reinforced Al based metal matrixcomposites by powder metallurgy (P/M) technique and investigation of their laser welded. Forthis purpose, homogenous powder mixtures were prepared by mixing 0, 5, 10, and 20 % weightratios of SiC particles with Al99, AlCu4MgSi ve AlMg1SiCu. Commercial same propertiesmaterials have been assured for comparision. The 10x10x60mm blanks were produced bypressing of powder mixtures in a floating single-effect die at 500 MPa pressure. Metal matrixcomposite (MMC) specimens were obtained at 400 C for 20 minutes and then the blanks in afurnace at 600 and 620 ºC for 40 minutes.Specimens have been tapered 5mm for good welding depth. Laser welding obtained on 2500 Wpower laser welding machine.Laser welding velocity have been selected 0,1; 0,3; 0,5 ve 0,7 m/min.The mechanical properties of the composite specimens were determined by measuring thedensity, hardness and transverse rupture strength values. Microstructure, machined surfaces,fractural sections and matrix/particle interface bonds were investigated by using optical andscanning electrone microscopes (SEM). The relationship between microstructure and laserwelding characteristics were determined. Protective gas has been used helium at 20 l/min. Thenlaser welding process, precipitation age hardening has been applied AlCu4MgSi-SiC veAlMg1SiCu-SiC composites. The density of the composites increased by increasing the ratio ofSiC reinforcing element. Nevertheless, the theoretical density (%) of the composites decreasedby increasing the SiC reinforcing ratio due to high porosity level. It was also found that thecompressibility behaviour negatively affected by increasing SiC reinforcing ratio.Experimental results showed that the transverse rupture strength decreased by increasing theSiC reinforcing ratio which resulted in an increase in hardness.Mechanical properties of specimens increased by precipitation age hardening has been appliedAlCu4MgSi-SiC ve AlMg1SiCu-SiC composites.oOn the Al99-SiC composites sintered at 600 C and laser welded at 0,3 m/min.by increase ofSiC ratio, hardness was increase from 47,7 HV to 98 HV.For AlCu4SiMg-SiC composites 0,5 m/min. laser welding velocity is good velocity for highhardness.oAt Laser welded AlMg1SiCu-SiC composites sintered on 600 C with increase of SiC ratiotransverse rupture strength wasnt change. Fracture of Al matrix is ductile fracture.XIII