Effect of Shielding Gas on Microstructures and Mechanical Properties of TC4 Titanium Alloy Ultranarrow Gap Welded Joint by Laser Welding with Filler Wire

A 20 mm thick TC4 titanium alloy plate was welded by ultranarrow gap laser welding with filler wire with Ar and He as shielding gas, respectively. A characterization analysis of the microstructures and mechanical properties of the welded joint was conducted with OM, SEM, XRD, and EBSD and through the microhardness test and tensile test. The results showed that HAZ of the welded joint formed with Ar as shielding gas was much wider than that with He, and weld microstructure composition with the two shielding gases was basically consistent; phase boundary of the weld metal obtained with Ar was clearer, with a larger misorientation between the laths; α′ martensite lath in weld metal prepared with He showed obvious preferred orientation distribution, and α′ martensite microstructure was much finer; the misorientation of α′ phase grain boundary of weld microstructure prepared with Ar was slightly less distributed in high angle grain boundary than that with He; tensile property of the welded joint prepared with He was better than that with Ar; the hardness of each zone of welded joint prepared with He was less fluctuated and the hardness value measured was slightly higher than that with Ar.

The Weld Microstructure and Mechanical Properties of the Alloy 52 and Its Variants with Applied Electromagnetic Stirring during Welding

This study investigated the impact of electromagnetic stirring (EMS) on nickel-base alloy welds prepared with the gas tungsten arc welding process. Alloy 52 and its variants, Alloy 52M and Alloy 52MSS, were carefully evaluated with their weld microstructure and mechanical properties. The results showed that the welds exhibited a typical microstructure of dendrites, and that the dendrites could be refined by electromagnetic stirring. Meanwhile, with an application of EMS, the precipitates became smaller and more evenly distributed in the inter-dendritic areas. Ti(N,C)s, Nb/(Nb,Si)Cs, and large-scale Laves phase with (Nb,Mo,Ti)Cs were the precipitates present in the Alloy 52, Alloy 52M, and Alloy 52MSS welds, respectively. With the refined microstructure, both Alloy 52 and Alloy 52M welds were observed to have an increase in their tensile strength, with a decrease in their elongations. Comparatively, for the Alloy 52MSS weld, the tensile strength was enhanced along with a slight increase in elongation. Deep and dense dimples were a dominant feature of low-Nb-additions welds, and dendrite-like features were found prevalent among the Alloy 52MSS welds. With EMS, the dimples of Alloy 52 welds and the dendrite-like features of Alloy 52MSS welds became finer, while the dimples of Alloy 52M welds grew coarser.

Structural investigation of the Plasma Transferred Arc hardfaced glass mold after operation

The paper presents the results of research aimed at detecting the causes of premature wear of molds for glass shaping, manifesting the formation of pits in the Plasma Transferred Arc pad-welds in which the working surface of the mold was shaped. The weld microstructure was tested, the chemical composition was determined in the pad-weld’s cross-section, linear and surface chemical distributions were made in the pad-weld’s cross-section, the surface morphology in damaged areas, and the chemical composition of surface inclusions were examined. The too high temperature of formed glass associated with wettability of the glass of the mold was indicated as the primary cause of premature mold wear.