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Abstract: The TiB2 particulate reinforced magnesium matrix composites (MMCs) were fabricated by adding a TiB2–Al master alloy processed via self-propagating high-temperature synthesis (SHS) reaction of Al–Ti–B systems with the different molar ratio of Ti to B (n Ti:n B =1:2 and n Ti:n B =1:2.5, respectively) to molten magnesium and using the semisolid slurry stirring technique. When the molar ratio of Ti to B is 1:2 in TiB2–Al master alloy, the TiB2–Al master alloy and TiB2p/AZ91 composites contained a certain amount of transient TiAl3 phase; however, when the molar ratio of Ti to B is 1:2.5, the TiAl3 phase was almost completely eliminated and the distribution of TiB2 particulates generally appeared to be more homogeneous throughout the magnesium matrix. [Copyright &y& Elsevier]

Magnesium metal matrix composites (MMCs) reinforced with various fractions of 10, 15 and 20 vol.% B4C particulates fabricated by powder metallurgy (P/M) technique were investigated. Microstructure characterization of the composites revealed necklace distribution of B4C particulates in the matrix material and the presence of minimal micro-porosity. The X-ray diffraction (XRD) showed the formation of MgO and MgB2 in B4C/Mg composites. Moreover, the results revealed that the hardness and wear resistance of the composites were higher than those of as-cast Mg ingot and increased with increasing amount of B4C particulates from 10 to 20 vol.%. [Copyright &y& Elsevier]

Abstract: Addition of Al can lead to the invalidation of KBF4 modification on the primary Mg2Si in Mg–5Si alloys and thus promote the preferred growth of the primary Mg2Si dendrite crystal. This may be due to the decrease or exhaustion of B in the melts by the formation of AlB x . [Copyright &y& Elsevier]

The synthesis of in situ formed TiB2/Mg composite utilizing the self-propagating high-temperature synthesis (SHS) reaction that occurred between the molten magnesium and green preforms consisting of Al, Ti and B powders was investigated. The result shows that it is feasible that the smelting temperature of the magnesium matrix alloy is selected at 860 °C, which is slightly higher than the exothermic reaction temperature of 852 °C on the DTA curve, prepared for the SHS reaction in the Al–Ti–B system. An as-cast microstructure of the composite reveals a relatively uniform distribution of TiB2 particulates with hexagonal or rectangular size of ∼2.0 μm. Furthermore, an analysis of the powders extracted from the TiB2/Mg composite confirms that a small amount of blocky TiAl3 phase is also present in the composite. [Copyright &y& Elsevier]

The effect of Al content on the self-propagating high-temperature synthesis (SHS) reaction of the Al–Ti–C preform in molten magnesium was investigated. As the Al content in the preforms was increased over the range of 20–40 wt.%, the TiC particulate sizes decreased from ∼5.0 to ∼1.0 μm. Microstructural characterization of the TiC/Mg (AZ91D) composite showed relatively uniform distribution of TiC particulates in the matrix material and the presence of minimal micro-porosity. [Copyright &y& Elsevier]