Aluminum Alloy Tailoring Tailor Welded Blanks, Laser Welding Technology

Tailor-welded Blanks are comprised of two or more separate pieces of sheet mental with different materiel and different thickness that have been welded together previous to stamping. The use of Tailor-welded Steel Blanks in Automobile industry has gotten a great economic efficiency. But Tailor-welded Aluminum Blanks have still not been used in automobile. There are many difficulties in Laser welding of Aluminum Blanks. Laser welding of Tailor-welded Blanks with butt joint is more difficult than lap joint. Because the laser beam is very sensitive to the groove gap and the welding blanks have different materiel and different thickness, there are more problems in butt welding of Tailor-welded Blanks, such as difficulty of weld molding, odds in heated and stress centralization.In this thesis, laser welding of tailored blanks with different thickness of two kinds of materials (5A02 and 5A06) with metal powder and without metal powder were carried out. Influence factors on laser absorption geometry and quality of weldment (surface coating, type of aluminum alloys, power of laser apparatus, weld speed and defocused distance etc) were also analyzed. Meanwhile, the causes of porosity and cracking were described. As well as, mechanical properties (tensile strength and hardness)were test. Micro structural characteristics and fractography were observed by SEM.The result of test indicated that the metal powder of Mg and Al can improve absorbability of aluminum alloys. The width of aluminum 5A02 and 5A06 alloys welds with metal power was wider than that with not metal power, when using the same weld condition. The hardness of 5A02 and 5A06 welds with metal power was harder than that without metal power, because the magnesium of metal powder can amend the loss of magnesium. The longitudinal tension PM specimen of Tailor Welded Blanks of 5A02 and 5A06 were all fractured on the thinner base metal, which indicated that welds were eligibility. The fracture of the longitudinal tension PM specimen was toughness fracture.