Structure In Fusion Zone Research Articles

Basic study on laser welding of Ag-Pd-Cu-Au alloy. Part 3. Factors on mechanical properties

In case of laser welding of same metals, the mechanical properties of weld show a little difference from that of base metal. This article discribes metallurgical studies on several factors which affect mechanical properties of laser weld. In order to study about rapid thermal hysteresis, the changes of the age hardening curves in various solution treatment and of ageing temperature and time, a difference between fusion zone and base metal using X-ray diffractometer, thermal hysteresis around fusion zone, the change of metal component by evaporation and metallographic structure of fusion zone were examined. Additionally, the studies on the appearance of blowhole and crack, and on the area of heat affected zone were performed.Ageing curve of Ag-Pd-Cu-Au alloy varied with solution treatment temperature. The fusion zone by laser irradiation was one supersaturated solid solution, while solution treated base metal precipitated into two solid phases. The increase in temperature around the fusion zone was restricted only in very narrow area, and no heat affected zone was found. In fusion zone, silver component was decreased. Crack regarded as stress corroision crack and blow hole appeared in the weld.

Weldability and hot cracking in thorium-doped iridium alloys

Abstract Modified iridium alloys containing ≥ 100ppm Th were found to be very susceptible to cracking during gas tungsten-arc and electron-beam welding. However, the electron-beam welding process showed greater promise of success in welding these alloys, in particular Ir–0·3W doped with 200ppm Th and 50ppm Al. The weld ability of this particular alloy was extremely sensitive to the welding parameters, such as beam-focus condition and welding speed, and the resulting fusion-zone structure. At low speeds successful electron-beam welds were made over a narrow range of beam-focus conditions. However, at high speeds successful welds can be made over an extended range of focus conditions. The fusion-zone grain structure is also a strong function of welding speed and focus condition. Weld-metal cracking was found to be caused by the combined effects of heat-affected-zone liquation cracking and solidification cracking. Scanning electron microscopic analysis of the fractured surface revealed patches of low-melting...