Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

Microstructure and mechanical properties of newly developed aluminum–lithium alloy 2A97 welded by fiber laser

Abstract: The newly developed aluminum–lithium alloy 2A97 was for the first time joined by laser beam welding in order to meet the ever-increased long-term requirements of aerospace, aviation and armament industries. The weld appearance, microstructure, solute segregation, precipitate behavior, and their relationships with mechanical properties of welded joints were investigated. Sound joints with no crack and a few small porosities are obtained under appropriate heat inputs. As a result of heterogeneous nucleation involving the effect of Zr and Li, a non-dendritic equiaxed zone forms between partially melted zone and fusion zone. The crystal morphologies in fusion zone vary from columnar dendrite to equiaxed dendrite, with the increase of constitutional supercooling. Solute segregation leads to the variations of Cu content in grain interior and boundary, as well as the weak ability of re-precipitation of fusion zone. Most precipitates in the base metal dissolve during welding, and fusion zone contains a decreased quantity of δ ′, β ′, θ ′, and T 1 . The ultimate tensile strength of laser welded joints is 83.4% of that of the base metal, and can meet the application requirements from related industries, but the ductility still needs to be improved. Welding defects and loss of solid solution/precipitation hardened structure lead to the degradation of mechanical properties. Tensile fracture occurs in weld with the brittle intergranular dominated mode and premature failure occurs and extends in the equiaxed zone.

Effect of heat input on heat affected zone cracking in laser welded ATI Allvac 718Plus superalloy

Abstract: The heat affected zones (HAZs) of low and high heat input laser welds of a newly developed superalloy, ATI Allvac 718Plus, were studied. Low heat input welds suffered significant HAZ grain boundary liquation cracking, while no cracking was observed in spite of a more extensive HAZ intergranular liquation in the higher heat input welds. Combination of lower welding stresses generated during cooling, and relaxation of these stresses by thick intergranular liquid were suggested to be the factors that contributed to the absence of cracking in the high heat input welds. Further, healing of some of the HAZ cracks in lower heat input welds by fusion zone interdendritic liquid occurred through liquid backfilling.

Microstructure and mechanical properties of AA7075(T6) hybrid laser/GMA welds

Abstract: The weldability of AA7075 using a hybrid laser/gas metal arc (GMA) welding process was examined. After welding process optimisation, the influence of filler wire composition, natural ageing, artificial ageing and a short duration solution heat treatment was investigated to enhance weld microstructural and mechanical properties. Results show that after a short solution heat treatment, a large fraction of the dendrite boundaries in the weld fusion zone dissolved in the primary phase. Tensile tests and micro-hardness tests show that the weld has a comparable strength to the T6 base alloy when welding with an AA2319 consumable. Fracture surfaces observed under a scanning electron microscope indicate a large number of fine ductile type voids and larger sized dimples. The improved ductility of the weld together with the strength comparable to the base alloy make the weld more formable than none solution heat-treated welds.

Penetration increase of AISI 304 using ultrasonic assisted tungsten inert gas welding

Abstract: Ultrasonic assisted tungsten inert gas (U-TIG) welding method was developed. Both U-TIG and conventional TIG welding of AISI 304 stainless steel with 5 mm thickness were experimentally studied in this paper. The results show that the penetration depth is increased up to 300% for weld made with U-TIG welding compared with conventional TIG welding. Ultrasonic energy enhances arc push force, causes a continual high frequency oscillation in the arc plasma and increases welding penetration. These effects are thought to be responsible for enhancing the welding efficiency and improving the appearance of stainless steel weld joints.