Microstructure and mechanical properties of gas-tungsten-arc (GTA)-welded Ti-15V-3Cr-3Sn-3Al alloy in direct current electrode negative mode are characterized. The thermal profile was measured during welding with continuous current (CC) and pulsed current (PC) at different frequencies. A single-step postweld aging of the welded samples at subtransus temperature was attempted to study precipitation of alpha phase. Two different morphologies of alpha phase are observed along with a partitioning of alloying elements into the two phases. Processing conditions for higher strength are identified and correlated with the thermal profile. Microstructure changes due to postweld heat treatment were characterized.

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In the current study, a novel approach that integrated in situ and ex situ reinforcement techniques was used to develop a hybrid AA7475 aluminium metal matrix composite (MMC). The primary objective of this study was to explore the viability of producing in situ TiB2 particles and adding ex situ B4C particles as reinforcements in the same melt of the aluminium alloy AA7475, with the intention of using these ceramic fillers to improve the mechanical properties of bare AA7475. For in situ particle synthesis, salts such as K2TiF6 and KBF4 were used and for ex situ, B4C particles are utilized. The aluminium MMC was prepared using stir casting method and characterized using ASTM standards. For comparison, composite with only in situ TiB2 particles and composite with only ex situ B4C particles were also fabricated. According to the results, the highest tensile strength of 156.57 MPa was achieved for the hybrid composite made using 5wt% of B4C and TiB2. Similarly, the highest hardness of 144.67 HV was observed for the same. However, the presence of both TiB2 and B4C improved the hardness together. The microstructure shows highly refined phases of the matrix and also the formation of precipitates and reinforcements clearly. The EDAX and XRD confirm the intermetallics formation and dispersion of particles within the matrix material. This aluminium composite with improved properties could be used in automotive, aircraft and in defense sectors where lightweight and high strength materials are required.

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