Papers by Author: Chun Huan Chen

Abstract: Cemented carbide YG30 and steel 1045 were welded with various Ni-Fe-C filling alloys via the Cemented carbide YG30 and steel 1045 were welded with various Ni-Fe-C filling alloys via the tungsten-inert-gas (TIG) arc welding. η phase formation at the welding joints was investigated via scanning electronic microscope (SEM), transmission electronic microscope (TEM) coupled with selected diffraction, and electron probe microanalysis methods. η phases in three different morphologies were identified and they appeared to form in different mechanisms. The η phase formed at the heat-affected zone (HAZ) exhibited a similar size to that of WC particles and its formation was mainly attributed to the inter diffusion among W, C and Fe, Co, Ni in solid-state γ phase. The large-size η phase near the interface between YG30 and weld bead was due to the coarsening of tiny η grains in the liquid weld bead. The small-size η phase was formed via precipitation from the γ phase during cooling. The η phase formation could be controlled by optimization of C and/or Ni concentration in the filling alloys.

Abstract: The linear friction welding (LFW) performance of hydrogenated Ti-6Al-4V alloy was investigated. The effects of hydrogen on macro-features and axial shortening as well as microstructure of Ti-6Al-4V alloy joints welded by LFW were analyzed. The mechanical properties of joints after dehydrogenation were also examined by tensile test at room temperature. The results indicated that the hydrogenated Ti-6Al-4V specimens containing 0.3~0.4 wt% hydrogen had a better microstructure and plastic deformation ability, which resulted in the optimum welding performance improvement of LFW. The critical power input of LFW could be lowered by addition of hydrogen to Ti-6Al-4V alloy. The results of tensile test showed that joints which experienced thermohydrogen processing possessed the same tensile strength and plasticity as original joints.