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Abstract: The W–15wt.% Cu composite powders were synthesized by a sol–gel method combining with hydrogen reduction. X-ray diffraction patterns show that pure W and Cu phases were obtained at a reduction temperature of 750°C for 2h. The particle size of such powder is in the range from 100 to 400nm and in each particle the W and Cu phases are seemingly mixed homogeneously in the nanometer scale. The powders were microwave sintered for 25min at different temperatures of 1050, 1150 and 1200°C, respectively. The results show that W–15wt.% Cu samples microwave sintered at 1200°C exhibit a relative density higher than 97% and an average particle size of W as small as 600nm. The thermal conductivity and the Vickers microhardness of the sintered W–15wt.% Cu samples are in the range from 140 to 187W/mK and from 235 to 347HV, respectively. [Copyright &y& Elsevier]

Abstract: The use of dual phase (DP) steels in the automobile industry unavoidably involves welding and dynamic loading. The aim of this investigation was to evaluate the microstructural change and mechanical properties of laser welded dissimilar DP600/DP980 steel joints. The dissimilar joints showed a significant microstructural change from nearly full martensite in the fusion zone (FZ) to the unchanged ferrite–martensite dual-phase microstructure in the base metal. The welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat-affected zone (HAZ). The dissimilar welded joints were observed to exhibit a distinctive unsymmetrical hardness profile, yield-point-like phenomenon, and single-stage work hardening characteristic, with yield strength and work hardening rate lying in-between those of DP600 and DP980 base metals, and ultimate tensile strength equivalent to that of DP600 base metal. Although the welded joints showed a lower fatigue limit than the base metals, the fatigue life of the welded joints at higher stress amplitudes was almost the same as that of the DP600 base metal. The welded joints failed in the soft zone at the DP600 side under tensile loading and fatigue loading at the higher stress amplitudes. Fatigue crack initiation occurred from the specimen surface and crack propagation was characterized by typical fatigue striation together with secondary cracks. [ABSTRACT FROM AUTHOR]

Abstract: Following laser hole sealing the hardness of CP1 Ti welds was found to be directly related to the microstructure. It was observed that welds made with electrolyte present had a microstructure which consisted mostly of the acicular alpha phase compared to welds made without electrolyte which had a mixed structure of serrated alpha, platelet alpha and acicular alpha phases. The hardest regions of welds made in the presence of electrolyte consisted of a fine colonized acicular alpha phase. Results from energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis further suggested that an increase in the composition of interstitial elements was the primary mechanism responsible for increased hardness when welding with electrolyte present. [Copyright &y& Elsevier]