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Abstract: Reaction behaviors and products of thermal explosion reaction from Ni–Ti–C system under air and Ar atmosphere were investigated, respectively. The ignition temperature for the thermal explosion reaction under air is much lower than that under Ar atmosphere. Under two atmospheres, increasing the Ni content and Ti particle size can increase the ignition temperature, respectively. Under air, increasing Ni and C particle sizes can decrease the ignition temperature, but the opposite results are achieved under Ar atmosphere. The reaction products are mainly dependent on the C particle size under two atmospheres. [Copyright &y& Elsevier]

Abstract: The effect of Al–P–Ti–TiC–Nd2O3 modifier on the microstructure and mechanical properties of hypereutectic Al–20wt.%Si alloy has been investigated. It has been concluded that Nd2O3 in Al–P–Ti–TiC–Nd2O3 modifier can modify primary silicon in hypereutectic Al–Si alloys. Statistical analysis shows that primary silicon size (approximately average 38μm) in modified Al–20wt.%Si alloy with Al–P–Ti–TiC modifier is larger than that (approximately average 20μm) in modified Al–20wt.%Si alloy with Al–P–Ti–TiC–Nd2O3 modifier. Compared with primary silicon modified with Al–P–Ti–TiC modifier, Primary silicon modified with Al–P–Ti–TiC–Nd2O3 modifier has the smaller size at different holding times such as 10, 60 and 120min. The internal defects in coarser primary silicon particles play an important role in determining the tensile strength and elongation of the materials. Coarser primary silicon particles in unmodified Al–Si alloys can degrade the loading bearing capacity of the materials. Modification can eliminate the internal defects to a great extent and improve the tensile strength and elongation of hypereutectic Al–Si alloys. Compared with unmodified and heat-treated Al–20wt.%Si alloy, the tensile strength of the modified with Al–P–Ti–TiC–Nd2O3 modifier and heat-treated Al–20wt.%Si alloy increases by 20%. [Copyright &y& Elsevier]

Abstract: Single crystals of Co50Ni20FeGa29 with B2 phase have been obtained in a deep supercooling condition. The interface-facets and the segregation effect lead to the formation of ordered defects that store a directional internal stress. These defects give to a large energy barrier that leads to a very sharp martensitic transformation within a temperature window of only 2K. The single crystals show good shape memory effect and superelasticity, which are anisotropic between the growth direction [001] and its equivalent direction [010]. The anisotropic behaviors are attributed to the directional internal stress caused by the ordered defects. [Copyright &y& Elsevier]

Abstract: In the Co39Ni33Al28 alloy, the ferromagnetic shape memory effect was investigated. A martensitic transformation (MT) occurred in the Co39Ni33Al28 alloy when the temperature was lower than the martensitic start transformation temperature, M S =233K. The morphologies and microstructures of the martensitic phase characterized by transmission electron microscope (TEM) showed a new 28-layered (28M) modulated martensite consisting of pinstripes and co-existing with the non-modulated martensite. Anomalies in magnetic properties and strain emerging around the MT have been briefly discussed. [Copyright &y& Elsevier]

Abstract: The solid-state reaction behavior of the Al–Ti–C powder mixture compacts was investigated. The results showed that the TiC/Al composite was synthesized by the solid-state diffusion reaction in a vacuum electric resistance furnace at a heating temperature of 600±2°C, with a holding time for 3h. The TiC particulate was fine and irregular, with a mean size of 2μm. [Copyright &y& Elsevier]

Abstract: The modification effect of KBF4 on the primary and eutectic Mg2Si in Mg–Si alloy is better than that of K2TiF6. This may be the reason of the presence of B in melts. However, the modification effect of KBF4 is greatly weakened by the simultaneous addition of K2TiF6 due to the decreasing of B content in the melts by the formation of TiB and TiB2. [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: Magnesium metal matrix composites (MMCs) reinforced with 10, 20 and 30 vol.% TiB2 particulates, respectively, were fabricated by powder metallurgy. The microstructure, porosity, hardness and abrasive wear behavior of the composites were evaluated. Microstructural characterization of Mg MMCs showed generally uniform reinforcement distribution. As compared with pure Mg, the hardness (HB) values of Mg MMCs reinforced with 10, 20 and 30 vol.% TiB2 particulates were increased by 41%, 106% and 181%, respectively. The abrasive wear tests showed that the wear resistance of Mg MMCs is increased with the increasing of the reinforcement volume fraction. This was due to the strong particulate-matrix bonding and high hardness of the TiB2 particulate. [Copyright &y& Elsevier]

A TiB2 particulate reinforced magnesium matrix composite (MMCs) was fabricated by adding a TiB2–Al master alloy processed via self-propagating high-temperature synthesis (SHS) reaction in Al–Ti–B system into molten magnesium and using the stir casting technique. The results showed that the TiB2–Al master alloy and TiB2/Mg composite contained a certain amount of transient TiAl3 phase. When the Al–Ti–B system was incorporated with an appropriate C, TiB2 and TiC reinforcing phases were simultaneously synthesized and the TiAl3 phase was almost completely eliminated. [Copyright &y& Elsevier]

Abstract: The Mg–30B2O3 modifier with the composition of Mg and B2O3, sintered in the temperature range between 250 and 450°C, has been developed as a low-cost and effective modifier for hypereutectic Mg–Si alloys. With 0.2–1.0wt.% B (introduced in the form of Mg–30B2O3), the morphology of the primary Mg2Si transforms from coarse dendrite shape into fine polyhedral shape with the size about 10μm. The modification mechanism of B2O3 is attributed to the adsorption and poisoning manners due to the presence of B in the melts by the decomposition of B2O3. [Copyright &y& Elsevier]

Abstract: The effects of different processing parameters, such as heating rate, isothermal temperature and isothermal holding time, on the semisolid microstructures of the AZ91D alloy during partial remelting had been investigated in the present paper. The experimental result showed that the high heating rate shortened the growth process of renascent recrystal grains in the deformed alloys, which ultimately attributed to refine the globular α-Mg grains in the evolved semisolid microstructure. The liquid volume fraction f L of the semisolid slurry gradually enlarged with the elevating of isothermal temperature during partial remelting. The isothermal temperature between 560°C and 580°C for 30min was adequate for the AZ91D to produce an ideal semisolid slurry with liquid fraction range between 32% and 52%. During the partial remelting, it would experience a relatively long holding time that the liquid and solid phases reached a state of dynamic equilibrium in the semisolid slurry. For the AZ91D alloy, the isothermal holding time of 30min was relatively adequate for the present experiment. During the partial remelting, the primary irregular grains gradually spherodized under a function of interface curvature. Oswald ripening mechanism, a dissolution and reprecipitation diffusion-controlled growth, could account for the coarsening of globular grains in the present experiment. The spheroidization and coarsening evolution processes of solid particles in the semisolid slurry were deduced and elucidated by the corresponding simulant formulae in the present paper. [Copyright &y& Elsevier]

A method is proposed to estimate quantitatively the shifting distance of the eutectic point in a horizontal direction (under non-equilibrium solidification condition). The shifting distances of the eutectic point in Al–20wt.%Si alloys under the non-equilibrium solidification condition are 0.4 and 0.9wt.% in a horizontal direction towards higher silicon contents with the addition of 0 and 3wt.% master alloys (Al–20wt.%Y2O3), respectively. [Copyright &y& Elsevier]

The effect of predeformation on the semisolid microstructure of Mg–9Al–0.6Zn (AZ91D) alloy is investigated. The results indicate that finer, more globular semisolid microstructure was attained in more heavily deformed alloys after heat treatment at 560 °C for 20 min. Furthermore, the liquid islands in the grains also become less with the increase in the compression ratio. It is mainly because the microstructural evolution mechanisms are different in alloys with various compression ratios. The heavy predeformation leads to the occurrence of the recrystallization, and the amount of recrystallization increases with the increase of the compression ratio. These recrystallization grains can easily give rise to the small initial grains that evolve towards a globular and small morphology rapidly during isothermal heat treatment at semisolid temperature of 560 °C. Moreover, there are also no liquid islands in the final grains after evolution. In addition to the recrystallization evolution mechanism, there are two other microstructural evolution mechanisms—melting and combining of dendritic arms, which are both discussed in this paper. [Copyright &y& Elsevier]