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.

Effect of Nd-YAG laser welding on the functional properties of the Ni–49.6at.%Ti

Abstract: Laser welding technology is applied successfully for joining several metallic compounds. Using a Nd-YAG source the process is suitable for precision welding of low thickness metallic sheets. In this work a Nd:YAG laser was used for welding 0.54 mm thick tapes of Ni–49.6at.%Ti shape memory alloy (SMA). Two different microstructural states of the material were chosen (fully recrystallized and partial annealed after 30% cold working) to investigate pseudoelastic and shape recovery behaviours. For the two different metallurgical conditions the mechanical properties of both reference and laser welded samples were tested at several temperatures by stress–strain measurements. A systematic comparison of the results was carried out. Moreover, differential scanning calorimeter (DSC) investigations on samples taken from the heat affected zone and hardness measurements allowed further clarification that the modification was induced by the welding procedure. The results obtained on the fully recrystallized material indicate that the stress-induced martensite and the recovery mechanisms are weakly modified by the presence of the welding zone while the pseudoelastic properties of the partial annealed material are strongly affected.

Effect of vacuum on penetration and defects in laser welding

Abstract: The effect of vacuum on weld penetration and porosity formation was investigated in high-power cw CO2 and YAG laser welding. It was consequently confirmed in welding with both lasers that the penetration was slightly deeper in aluminum alloys and austenitic stainless steel with a decrease in the ambient pressure. It was also revealed that no porosity was present in the materials welded at lower pressures. The reason for no porosity formation in vacuum was examined by observing keyhole behavior, bubble and porosity formation situation, and liquid flow in the molten pool during high-power YAG laser welding under various conditions through the microfocused x-ray real-time observation system. It was confirmed in the coaxial Ar or He shielding gas that a lot of bubbles were generated near the bottom part of the molten pool from the tip of a fluctuated keyhole and resulted in large pores. On the other hand, under the vacuum conditions, no bubbles were formed in the melt pool from the keyhole, although the middl...

Joint properties of friction stir welded AZ31B– H24 magnesium alloy

Abstract: The weldability of friction stir welded hot rolled AZ31B-H24 magnesium alloy sheet, 4 mm in thickness, was evaluated, varying welding parameters such as tool rotation speed and travel welding speed. Sound welding conditions depended mainly on sufficient heat input during the welding process. Insufficient heat input, which was generated in the case of higher travel speed and lower rotation speed, caused an inner void or lack of bonding in the stir zone. The microstructure of the weld zone was composed of five regions: base metal, heat affected zone, thermomechanically affected zone, stir zone I and stir zone II. Unlike the general feature of friction stir welded aluminium alloys, the grain size of the weld zone was larger than that of the base metal. Stir zones I and II were characterised by partial dynamic recrystallisation and full dynamic recrystallisation, respectively. The hardness of the weld zone was lower than that of the base metal owing to grain growth. A wider range of defect free weldin...