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Abstract: The dense TiC–TiB2/Ni composite was successfully fabricated via a simple route where the pressure assisted self-propagating high-temperature synthesis (SHS) was directly ignited at 625°C with the incorporation of air. The ignition temperature in air was much lower than that in vacuum (1040°C). The composites made in air possessed the similar phase constituents and microstructure as well as comparable mechanical properties to those made in vacuum. The ignition temperature both in air and vacuum showed a significant dependence on Ni content and reactant particle size while the reaction products only showed a dependence on Ni content and B4C particle size, irrespective of Ti particle size. The density of the composite made in air and vacuum only depended on Ni content while the mechanical properties of the composites made in air and vacuum both showed a similar dependence on the Ni content and reactant particle size. [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]

Abstract: The morphologies of primary silicon were studied in detail with different cooling rates and melt overheating temperatures. According to the present results, the morphologies of primary silicon are a strong function of the solidification conditions such as cooling rate and melt overheating temperature. With the elevation of melt overheating temperature, the morphologies of primary silicon will change from star-like and other irregular primary silicon to octahedral primary silicon and the size of primary silicon will gradually decrease. On the other hand, it can be safe to deduce that the Si–Si cluster of larger size should be beneficial for the formation of the nucleus of star-like and other irregular primary silicon and the Si–Si cluster of smaller size should be beneficial for the formation of the nuclei of octahedral primary silicon. With increasing cooling rate, the size of primary silicon will gradually decrease. If the cooling rate is lower than a certain (or critical) cooling rate, the cooling rate will have hardly effect on the morphologies of primary silicon in the solid state. If the cooling rate is higher than a certain (or critical) cooling rate, the cooling rate will play an important role in determining the morphologies of primary silicon in the solid state. [Copyright &y& Elsevier]

Abstract: Steel matrix composite locally reinforced with in situ synthesis of TiC particulate in the sand mould was fabricated successfully using the self-propagating high-temperature synthesis (SHS) reaction of Ni–Ti–C system during casting. The DTA result indicates that TiC could be formed during the SHS reaction of Ni–Ti–C system and Ni serves as a reactant in the SHS reaction of Ni–Ti–C system. As-cast microstructure of TiC locally reinforced region reveals a relatively uniform distribution of TiC particulates. Ni could be a diluent that might prevent the diffusion of carbon between TiC grains in the process of fabricating the composite. Compared to those of unreinforced steel matrix, the hardness and the wear resistance of the TiC locally reinforced steel composite enhanced 67.6% and 349%, respectively. [Copyright &y& Elsevier]

Abstract: The reactive infiltration synthesis of steel matrix composite reinforced with in situ TiB2–TiC particulates by the self-propagating high-temperature synthesis (SHS) reaction of the Ni–Ti–B4C system during casting was investigated. The as-cast microstructures of the in situ processed composites reveal a uniform distribution of TiB2–TiC particulates with a fine size of ∼5.0μm. Although, microstructural characterization shows the absence of macro-pores and blowholes, the Ni content in the system has a significant effect on the presence of micro-porosity in the composites. Moreover, the results show that the densities of the composites are lower than those of medium carbon steel and high-speed (HS) steel. Although, the hardness values of the composites are significantly higher than that of medium steel and lower than that of HS steel, the wear resistance values of the composites are higher than those of medium steel and HS steel. [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: In this study, a new Al–P–Ti–TiC–Y modifier has been successfully designed to modify primary silicon in hypereutectic Al–20wt.%Si and Al–29wt.%Si alloys. The results show that the morphologies of primary silicon crystals are drastically changed from irregular morphologies, such as starlike (fivefold) and coarse platelet to regular morphologies. Statistical analysis shows that primary silicon sizes in modified Al–20wt.%Si and Al–29wt.%Si alloys (approximately 20 and 35 μm, respectively) are smaller than those in unmodified Al–20wt.%Si and Al–29wt.%Si alloys (approximately 100 and 250 μm, respectively). As compared with unmodified Al–20wt.%Si and Al–29wt.%Si alloys, the Brinell hardness values of modified Al–20wt.%Si and Al–29wt.%Si alloys are increased by 15.8% and 32%, respectively. The wear rates of the modified Al–20wt.%Si and Al–29wt.%Si alloys are lower than those of the unmodified Al–20wt.%Si and Al–29wt.%Si alloys (under loads ranging from 3 to 9 N), respectively. [Copyright &y& Elsevier]

Abstract: The modification of in situ formed Mg2Si in Mg–Si alloys with yttrium (Y) was investigated. As-cast microstructure analysis of Mg–5wt.% Si alloys indicates that all the primary Mg2Si crystals are surrounded by a layer of α-Mg dendritic halos, which is again surrounded by the eutectic Mg2Si+Mg structures. When the Y content is 0.1 or 0.4wt.%, the sizes of primary and eutectic Mg2Si do not significantly reduce in Mg–5wt.% Si alloys. When the Y content is 0.8wt.%, the mean size of primary Mg2Si decreases from more than 100μm to about 30μm or less; furthermore, the Chinese script type Mg2Si particle also exhibits modified morphology as a fine fiber. When the Y content is further increased to 1.2wt.%, the primary Mg2Si becomes coarser again and even larger than that in the unmodified alloy; however, the eutectic Mg2Si still exhibits modified morphology as a fine size. The size and amount of Mg–Y point compounds are increased with the increasing of Y content in the alloys. In addition to distributing in α-Mg phase, the Mg–Y point compounds are also present in primary Mg2Si dendritic crystal. In the unmodified alloy, the coarse primary Mg2Si is formed by the preferred growth that occurs at the tips of branches; however, when the alloy is modified with 0.8wt.% Y, the preferred growth manner of the primary Mg2Si was depressed, while another type of growth, isotropic growth manner, is enhanced in the modified alloy. [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]

Partial remelting behaviors of Mg–11Al–0.5Zn alloy and TiB2/Mg–11Al–0.5Zn composite are investigated by the isothermal holding at the temperatures of 510 and 545 °C. The result shows that, although, the TiB2 addition has no influence on the remelting characteristics of eutectic and liquidus temperatures of the composite, it has a great effect on the remaining liquid located at the grain boundary. With a processing temperature of 545 °C, the remaining liquid is dramatically decreased in the composite, compared with that in the unreinforced matrix alloy. Furthermore, the solid α-Mg grain size in the composite does not significantly reduce compared with that in the matrix alloy; however, the microhardness of the α-Mg grain is increased in the partial remelting microstructure in the composite. Although most of the TiB2 particulates are present in the remaining liquid phases distributed at the grain boundaries, some liquid islands are entrapped inside α-Mg grains. As a consequence, the TiB2 particulates can eventually reside within the grains after complete solidification. However, it is difficult that TiB2 particulate is directly incorporated (engulfed) into the Mg–11Al–0.5Zn matrix alloy during the regular solidification process. Furthermore, the DTA, SEM and XRD results reveal that no reaction occurs between the TiB2 particulate and matrix alloy during the partial remelting process, which indicates that TiB2 particulate is thermodynamically stable at the Mg–11Al–0.5Zn matrix alloy. [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]

The synthesis of in situ formed TiC/Mg(ZM5) composite utilizing the exothermic reaction of the preforms consisting of Al, C and Ti powders in molten magnesium was investigated. The result showed that the reactant particle size has a great effect on the reaction. For a nano-size Al and C, and micron-size Ti powders system, in situ TiC/Mg(ZM5) composite was fabricated successfully. [Copyright &y& Elsevier]

Magnesium reinforced by in situ particulates was synthesized utilizing the self-propagating high-temperature synthesis (SHS) reaction of Al–Ti–C preforms in molten magnesium. The result showed that the preform preheat temperature has a great effect on the SHS reaction. For a preheat temperature of 450 °C, in situ TiC/Mg composite was fabricated successfully. [Copyright &y& Elsevier]

Magnesium reinforced by in situ particulates was successfully synthesized utilizing the thermal explosion synthesis reaction of Mg–Al–Ti–C system preforms in molten magnesium. The results show that aluminum content of preforms has a great effect on the reaction and as long as it is chosen adequately, tailored TiCp/Mg composites can be fabricated. [Copyright &y& Elsevier]

A TiC particulate reinforced magnesium matrix composite (PRMMC) was fabricated by adding a TiC–Al master alloy processed via self-propagating high-temperature synthesis reaction into molten magnesium and using the semi-solid slurry stirring technique. The properties of the PRMMC are higher than those of the unreinforced magnesium alloy. [Copyright &y& Elsevier]

Abstract: Dense high volume fractions of different molar TiB2/TiC ratios reinforced Fe matrix composite were successfully fabricated through the SHS reaction assisted with pressure. The reaction mechanisms for three systems were dissolution–precipitation. The TiB2 morphology changed from plate-like to clubbed and further to cubic with decreasing TiB2/TiC ratios from 2:1 to 1:2. The composites with 2:1 and 1:1 ratios of TiB2/TiC have a similar highest Vickers hardness and flexural strength while the composite with 1:1 ratio of TiB2/TiC has the best fracture toughness. The improvement of the fracture toughness was attributed to the reduction of thermal stress and the modification of TiB2 morphology. The optimal ratio of TiB2/TiC was recommended to be 1:1. [Copyright &y& Elsevier]

Abstract: In the present study, the effect of Nd on primary silicon and eutectic silicon in hypereutectic Al-20wt.%Si alloy has been investigated. It has been concluded that Nd in Al–P–Ti–TiC–Nd modifier can modify not only eutectic silicon but also primary silicon in hypereutectic Al-20wt.%Si alloy. Statistical analysis shows that primary and eutectic silicon crystallite sizes (approximately 60μm and 40μm in length, respectively) in modified Al-20wt.%Si alloy with Al–P–Ti–TiC modifier are about seven- and two-times larger than those (approximately 22μm and 18μm in length, respectively) in modified Al-20wt.%Si alloy with Al–P–Ti–TiC–Nd modifier, respectively. [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]

Abstract: The dense TiC–TiB2/Ni composite was successfully fabricated through the pressure-assisted thermal explosion reaction from Ti, B4C and Ni powder blends in air. The ignition temperature (625 °C) in air was 415 °C lower than that in vacuum. The decreased ignition temperature resulted from a chemical oven mechanism in which the oxidation and nitrification of Ti and the oxidation of B4C released the heat and promoted the occurrence of the thermal explosion reaction. The composites prepared in air and vacuum had similar phase constituents and microstructure. Moreover, the composite prepared in air possessed comparable hardness, flexural strength and fracture toughness to the composite prepared in vacuum. [Copyright &y& Elsevier]

Abstract: The fabrication of medium carbon steel–matrix composites locally reinforced with in situ TiB2–TiC particulates using self-propagating high-temperature synthesis (SHS) reaction of Ni–Ti–B4C system during casting was investigated. X–ray diffraction (XRD) results reveal that the exotherm of 1042°C initiated by heat release of the solid state reaction in the differential thermal analysis (DTA) curve is an incomplete reaction in Ni–Ti–B4C system. As-cast microstructures of the in situ processed composites reveal a relatively uniform distribution of TiB2–TiC particulates in the locally reinforced regions. Furthermore, the particulate size and micro-porosity in the locally reinforced regions are significantly decreased with the increasing of the Ni content in the preforms. For a Ni content of 30 and 40wt.%, near fully dense composites locally reinforced with in situ TiB2 and TiC particulates can be fabricated. Although most of fine TiB2 and TiC particulates which form by the reaction–precipitation mechanism during SHS reaction are present in the locally reinforced region, some large particulates which form by the nucleation–growth mechanism during solidification are entrapped inside the Fe-rich region located in the reinforcing region or inside the matrix region nearby the interface between matrix and reinforcing region. The hardness of the reinforcing region in the composite is significantly higher than that of the unreinforced medium carbon steel. Furthermore, the hardness values of the composites synthesized from 30 to 40wt.% Ni–Ti–B4C systems are higher than those of the composites synthesized from 10 to 20wt.% Ni–Ti–B4C systems. [Copyright &y& Elsevier]

The precipitation kinetics during non-isothermal annealing of an Al-Mn alloy (AA3003) rolled over a large strain range ( ε = 0–2) has been investigated. Precipitation strengthening can overtake recovery softening when prestrained alloy was annealed below 573 K. The precipitate size distributions were similar in undeformed and prestrained alloys annealed at low temperature (673 K). We developed a coupled deformation-recovery-precipitation model for nucleation kinetics of heterogeneous precipitation. Strain-induced dislocations significantly promote nucleation at small and moderate strains while nucleation rate on sub-boundaries of higher misorientation increases by orders of magnitude with strain, and becomes dominant at large strains. [ABSTRACT FROM AUTHOR]

Abstract: In situ TiC particulates locally reinforced manganese (Mn) steel matrix composite was successfully fabricated via combustion synthesis of (Fe,Ti)–C system during casting. XRD results reveal that the phases of the composites consist of TiC, α-Fe and austenite. Microstructure of the locally reinforced manganese (Mn) steel matrix composite consists of three separate regions, i.e. a TiC particulate-reinforced region, a transition region, a steel matrix region. TiC particles in the reinforced region, having fine size of 2μm, are distributed uniformly. The hardness and wear resistance of the TiC particulates locally reinforced composites are much higher than those of quenched Mn13 steel. Furthermore, the microstructure formation mechanism of the composite was discussed. [Copyright &y& Elsevier]

Abstract: The microstructure, compression property and work-hardening effect of the NiAl-matrix composite reinforced by 5 vol.% ceramic particulates (TaB and TaB2) were investigated. The compression properties and work-hardening capacity (H c) under the different strain rates were also investigated. The NiAl-matrix composite has strong strain rate sensitivity. A high true ultimate strength of 1399 MPa, a true fracture strain of 18.7% and H c = 1.84 were obtained under the strain rate of 1.0 × 10−4 s−1. The good compression properties may be attributed to the refinement of the grain size and the good combination between the ceramic particulates and the NiAl-matrix. [Copyright &y& Elsevier]

Abstract: The microstructure, compression property and work-hardening effect of the NiAl-matrix composite with 1.7wt.% NbB2 and Nb x C (x =1 or 2) fabricated by the combustion synthesis and hot pressing technique have been investigated in the study. The NiAl-matrix composite has strong strain rate sensitivity. The yield strength of the NbB2–Nb x C/NiAl composite decreases while the fracture strain and the work-hardening capacity (H c) increase with decreasing strain rate. A high true ultimate strength of 1472MPa, a fracture strain of 20.1% and H c =1.41 were obtained under the strain rate of 2.0×10−5 s−1. [Copyright &y& Elsevier]

Abstract: Effect of C particle size on the mechanism of self-propagation high-temperature synthesis (SHS) in the Ni–Ti–C system was investigated. Fine C particle resulted in a traditional mechanism of dissolution-precipitation while coarse C particle made the reaction be controlled by a mechanism of the diffusion of C through the TiC x layer. The whole process can be described: C atoms diffusing through the TiC x layer dissolved into the Ni–Ti liquid and TiC were formed once the liquid became supersaturated. Simultaneously, the heat generated from the TiC formation made the unstable TiC x layer break up. However, with the spread of Ti–Ni liquid, a new TiC x layer was formed again at the interface between spreading liquid and C particle. This process cannot stop until all the C particles are consumed completely. [Copyright &y& Elsevier]

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: Creep behavior of the unmodified and modified cast Al–Cu alloys was investigated at temperatures from 393 to 483K in the tension test. The creep resistance ability of the Al–Cu alloy modified by Pr x O y is almost 3–5 times as high as that of the unmodified Al–Cu alloy, which is attributed to a large number of nano-scale θ′ precipitates with high thermal stability in the modified Al–Cu alloy restricting and impeding the dislocation movement during the creep. The induction of a threshold stress in the analysis leads to a stress exponent of 5, which suggests that the creep behavior of both the present alloys is associated with the lattice diffusion-controlled dislocation climb (n =5). [Copyright &y& Elsevier]

Abstract: Influence of Al addition on the products of self-propagating high-temperature synthesis (SHS) reaction in Al–Ti–Si system is investigated. When Al content is 0wt.%, the product only consists of Ti5Si3. When the Al addition is varied over the range of 5–15wt.%, the TiAl3 phase appears along with the Ti5Si3 phase. Besides Ti5Si3 and TiAl3, the transient phase Ti5Si4 is also detected in the final products when Al content increases over the range of 20–40wt.%. However, both the Ti5Si3 and Ti5Si4 phases disappear completely when Al content further increases to 50wt.%; only TiAl3 phase and trace of Al exist in the final products. Moreover, increase in Al content causes a decrease in Ti5Si3 and an increase in TiAl3 amount, which indicates that Al not only serves as a diluent but also participates in the SHS reaction process. Furthermore, the solubility of Si in TiAl3 increases significantly with Al addition increasing, while that of Al in Ti5Si3 mainly depends on the Al content in the Al–Ti–Si system. In addition, the Al incorporation has a great effect on the microstructure formation and evolution of the SHS reaction products. When Al content is less than 15wt.%, the final product mainly consists of Ti5Si3; however, which changes into Ti5(Si,Al)3 as Al content increases to 20–25wt.%, and then turns into another solid solution Ti(Al,Si)3 when Al content further increases to 30–50wt.%. Consequently, the microstructure evolution may be summarized as follows: Ti5Si3 →Ti5(Si,Al)3 →Ti(Al,Si)3. [Copyright &y& Elsevier]

Abstract: Influence of reactant (Cr, Ti and B4C) particle size on the SHS reaction products in 30wt.% Cr–Ti–B4C system has been investigated. Particle size of Cr powder has a significant effect on the phase compositions and microstructures of SHS reaction products. The SHS reaction in Cr–Ti–B4C system with nano-size Cr goes more complete and occurs more easily than that in the system with micron-size Cr. Increase in particle size of B4C powder has a little effect on the phase compositions of SHS reaction products, which consist of TiB2, TiC and Cr phases as well as transient phase Cr5B3 and a trace of C, but results in the increase of the amount of Cr5B3. Furthermore, the average sizes of TiB2 and TiC increase from ∼0.5 and ∼1μm to ∼2 and ∼3μm, respectively, as the B4C particle size increases from ∼3.5 to 40μm. Increase in particle size of Ti powder (∼38, ∼48 and ∼74μm) has little influence on the phase compositions of the products, as well as average sizes and morphologies of TiB2 and TiC. [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]

Abstract: The self-propagating high-temperature synthesis (SHS) reactions can take place in Cu–Ti–Si systems with Cu additions of 10–50wt.%, and the products only consist of Ti5Si3 and Cu phases, without any transient phase. In Ti–Si system, most of the Ti5Si3 grains synthesized exhibit the polygon-shaped coarse appearance with an obviously sintered morphology. When Cu content increases from 10 to 50wt.%, however, the Ti5Si3 exhibits cobblestone-like shape with a relatively smooth surface, and its average size decreases significantly from ∼15 to ∼2μm or less. The formation mechanism of Ti5Si3 in Cu–Ti–Si system is characterized by the solution, reaction and precipitation processes. Furthermore, the addition of Cu has a great influence on the volume change between green and reacted preforms. The volume change increases with Cu content increasing from 0 to 20wt.%, and then decreases with the content further increasing from 20 to 50wt.%. The addition of Cu to Ti–Si system significantly decreases the onset temperature of the reaction during differential scanning calorimetry process, which is even much lower than the α→β transition temperature of Ti (882°C), suggesting that the reaction could be greatly facilitated by Cu addition. As a result, the role of Cu serves not only as a diluent but also as a reactant and participates in the self-propagating high-temperature synthesis reaction process. [Copyright &y& Elsevier]

Abstract: The effect of Cr content on the self-propagating high temperature synthesis (SHS) reaction of Cr–Ti–C system has been investigated in this research. The thermodynamics calculation indicates that the TiC possesses higher thermodynamic stability than the Cr23C6, Cr7C3 and Cr3C2 phases, and the formation of TiC is the most exothermic. Additionally, the adiabatic combustion temperature (T ad) decreases with the increase of Cr content except for the phase transition regions. The XRD result shows that the type of products synthesized by SHS changes that a higher Cr content corresponds to higher chromium carbide. When Cr content is 10wt.%, only solid solution (Ti,Cr)Css is formed in the products. When Cr content increases to 20wt.%, besides (Ti,Cr)Css, the Cr7C3 phase is also detected. With the Cr content further increasing to 30 and 40wt.%, the products consist of (Ti,Cr)Css, Cr23C6, Cr7C3 and Cr, and therefore, much higher chromium carbide is synthesized. When Cr content reaches 50wt.%, however, the Cr7C3 disappears and the final products become (Ti,Cr)Css, Cr23C6 and Cr. Moreover, when Cr content increases from 10 to 20wt.%, the lattice parameter of (Ti,Cr)Css decreases, while it increases when the Cr content ranges from 20 to 50wt.%. Furthermore, the microstructure shows that the TiC particulate size decreases from ∼8 to ∼2μm with the increase of Cr content from 10 to 50wt.%, and the morphology shape of TiC particulate becomes more and more spherical. [Copyright &y& Elsevier]

Abstract: The SHS reaction behaviors of the Cu–Ti–B4C system with various Cu content were investigated. Theoretical calculation of the adiabatic temperatures reveals that the reaction in the Cu–Ti–B4C system is self-sustainable for the presence of 0–72.22wt.% Cu in the reactants without any preheat. With the increase of Cu content, the adiabatic temperatures, combustion temperatures and wave velocity decrease greatly, while the ignition time shows first a remarkable decrease and then an increase with the minimum value at 20wt.% Cu. Moreover, with the increase of Cu content, the sizes of the TiC and TiB2 grains decrease considerably. [Copyright &y& Elsevier]

Abstract: C particle size plays an important role in the ignition and combustion characteristics of the SHS reaction in the 20wt.% Ni–Ti–C system. When coarse C particles (∼38 and ∼75μm) are used, the SHS reactions consist of two different combustion stages with different brightness intensity of the combustion wave; XRD results indicate that the first and second combustion stages mainly correspond to the formation of Ni–Ti compounds and TiC ceramics, respectively. However, the final reaction is incomplete with a few Ni–Ti compounds and unreacted C. In contrast, when the fine C particle (∼1μm) is used, the SHS reaction consists of only one combustion stage with high brightness intensity of the combustion wave; XRD result indicates that final products consist of TiC and Ni, without any intermediate phase. With the decrease of C particle size, the wave velocities increase, and the ignition time becomes shorter. In addition, the morphology of TiC particulate changes to near-spherical, as C particle size decreases. [Copyright &y& Elsevier]

Abstract: The reaction path of TiC–TiB2 formation in 20 wt.% Cu–Ti–B4C powder mixtures was studied by using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Cu–Ti intermetallics (mainly Ti2Cu and TiCu) were formed initially via solid-state diffusion reactions between Cu and Ti particles; and then the Cu–Ti liquids were formed from the eutectic reaction between Ti2Cu and TiCu at about 965°C and the melting of the Ti2Cu. Cu–Ti liquid spread over the B4C and Ti particles, subsequently carbon and boron atoms from the bulk B4C continuously diffuse into the liquid phase to form liquid Cu–Ti–B–C. Finally, TiC and TiB2 particulates precipitate out of the saturated liquid. The exthermic reaction was complete after the addition of Cu. The results showed that Cu not only participated in the reaction, but changed the reaction path between Ti and B4C. [Copyright &y& Elsevier]

Abstract: The effect of Ni content on the products of Ni–Ti–B system via self-propagating high-temperature synthesis (SHS) reaction has been investigated in this research. The results show that the products of SHS reactions consist mainly of TiB2 and Ni. Besides, the transient phases of Ni4B3, Ni3B, NiB and Ni3Ti also exist in the final products, which means the SHS reactions of Ni–Ti–B system are incomplete. The change in the content of Ni within the chosen range from 30 to 70wt.% has little effect on the phase compositions of the final products. However, the sizes of TiB2 particulates have been greatly influenced by the Ni content. The average sizes of normal TiB2 particulates are nearly the same and about 4–6μm when Ni contents are 30, 40 and 50wt.%. Furthermore, TiB2 particulates in the products of these three systems present exaggerated growth and their sizes can even reach 10–15μm. The size of TiB2 particulates decreases dramatically to 1–2μm when Ni content increases to 60wt.% while to 0.6μm or less at 70wt.% Ni. The addition of Ni facilitates to form more liquid phases that are beneficial to TiB2 formation during SHS reaction process. The formation mechanism of TiB2 in Ni–Ti–B system can be characterized by the solution, reaction and precipitation processes. This can be further substantiated by the presence of remaining liquids, the typical hexagonal-prism morphology and the growth striation on (0001) crystal face of TiB2 particulates. [Copyright &y& Elsevier]

Abstract: The effects of different as-cast microstructures which were initially cast in graphite, metal, sand and firebrick moulds, respectively on the semisolid microstructure of AZ91D alloy, have been investigated during the strain-induced melt activation (SIMA) process. The experimental results showed that the moulds with high cooling capacity could produce the fine-grained as-cast microstructure in which the fine α-Mg dendrites were surrounded by a narrow layer of eutectic mixtures. After compressive deformation, in the fine-grained as-cast microstructure, the more systemic strain energy would be gradually accumulated and abundantly stored due to uniform inner crystal lattice distortion, so the recrystallization was easily induced by the stored strain energy at the elevated temperature. As a channel for the diffusion of atoms, the subgrain boundary along which Al element was enriched, foremost melted above the eutectic temperature and resulted in the separation of neighboring subgrains from primary dendrites. Therefore, the refining role of recrystallization on the microstructural evolution from dendrite to globular particles in morphology was easier to play in the fine-grained as-cast microstructure, which was advantageous for the production of fine-grained semisolid microstructure. Additionally, in the fine-grained as-cast microstructure, the melting fracture of narrow secondary dendritic arms was easy to occur in their roots, which also attributed to the production of fine globular grains in semisolid microstructure from primary dendrites. The finer dendrites in the initial as-cast alloy could evolve into the finer globular grains with relatively small grain size distribution range in the semisolid microstructure during partial remelting; therefore, the finer the dendrites in the initial as-cast microstructure, the better were the tensile properties of the evolved semisolid microstructure. [Copyright &y& Elsevier]

Abstract: The effect of Fe addition on the SHS reaction products of Fe–Ti–Si system was investigated. When Fe content is 0wt.%, the product only consists of Ti5Si3. As the Fe content ranges from 10 to 30wt.%, besides Ti5Si3 and Fe phases, the transient Fe2Ti is also found in the final products. With a further increasing Fe content of 40 or 50wt.%, however, in addition to Ti5Si3, Fe and Fe2Ti phases, the FeSi phase is also detected. Furthermore, the contents of Fe2Ti and FeSi phases as well as the solubility of Fe in Ti5Si3 also increase with the increasing of Fe content. This indicates that Fe not only serves as a diluent, but also participates in the SHS reaction process. Moreover, addition of Fe has a great effect on the microstructures of SHS reaction products. When Fe content is 10 or 20wt.%, the Ti5Si3 exhibits cobblestone-like shape. When Fe content is increased to 30wt.%, the Ti5Si3 particulates are finer and most of them are surrounded by the bonding agents. As the Fe content is further increased to 50wt.%, it is difficult to distinguish Ti5Si3 particulates from Fe and its compounds. The Ti5Si3 particulate sizes decrease from more than 6 to about 0.6μm or less when Fe content in the preforms ranges from 10 to 50wt.%. This is mainly due to the fact that the combustion temperature decreases with the increasing of Fe content. The addition of Fe provides more liquid phase for the Ti5Si3 formation during SHS reaction process. The formation mechanism of Ti5Si3 in Fe–Ti–Si system can be characterized by the solution, reaction and precipitation processes. This can be confirmed by the presence of bonding agents (remaining liquids), nearly spherical (cobblestone-like) morphology and relatively smooth surface of Ti5Si3 particulates, as well as the presence of growth striation on the surface of Ti5Si3 particulates. [Copyright &y& Elsevier]

Abstract: The solidification behavior of the cast TiB2 particulate reinforced AZ91 composite, including the cooling curve, microstructure and grain refinement effect, was investigated in the present study. Compared with the AZ91 alloy, the composite possessed lower nucleation temperature of primary α-Mg, almost the same eutectic reaction temperature and faster cooling rate during the total solidification time. The TiB2 particulates were pushed into the last solidified region and were surrounded by the eutectic Mg17Al12. The grain refinement effect in the TiB2/AZ91 composite can be attributed to the growth restriction effect exerted by TiB2 particulates and the faster cooling rate of the composite. [Copyright &y& Elsevier]

Abstract: The evolution process of TiC formation in the 20wt.% Cu–Ti–C powder mixtures was studied by using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The Ti x Cu y compounds (Ti2Cu, TiCu, Ti3Cu4 and TiCu4) formed initially via solid-state diffusion reactions between Cu and Ti particles; and then Ti2Cu and TiCu can form a Cu–Ti eutectic liquids at about 1233K. The unreacted Ti and C particles dissolved into the Cu–Ti liquids and led to the formation of Cu–Ti–C ternary liquids; subsequently, TiC particulates precipitated out of the saturated liquids. At the same time, also the formation of Ti2Cu occurred at the interface between the Cu–Ti liquids and the unreacted Ti particles. As the temperature increased further, the Ti2Cu melted and more Cu–Ti liquids formed; and then C particles continuously dissolved into the Cu–Ti–C liquids and TiC particulates gradually precipitated out of the saturated liquids. [Copyright &y& Elsevier]

Abstract: Reaction behaviors of self-propagating high-temperature synthesis (SHS) in the Ni–Ti–B4C systems with various Ni contents were investigated. The addition of Ni supports the initiation of ignition. Theoretical calculation of the adiabatic temperatures reveals that the reactions in the Ni–Ti–B4C systems are self-sustainable for the presence of 0–66.4wt% Ni in the reactants without any preheat. The Ni content plays a significant role in controlling reaction behavior and the constituents of the final products, but can not affect the ignition process greatly. With the increase of Ni content, combustion temperatures, wave velocities and ceramic particle sizes decrease, while the ignition time shows first a remarkable decrease and then an increase with the minimum value at 20wt% Ni. [Copyright &y& Elsevier]

Abstract: A metal matrix composite coating reinforced with TiC–TiB2 particulates has been successfully fabricated utilizing the in situ reaction of Al, Ti and B4C by the low oxygen partial pressure fusing technique to improve the wear resistance of Ti–6Al–4V alloy. The results show that increasing the B4C content is adverse to forming the coating for the formation of interfacial stress; however, the addition of TiC powder as a diluent can favor the formation of this coating and the addition of small amounts of Y2O3 can greatly improve the adhesion of the coating. After a pin-on-disc wear test, the wear mass loss of the coating is only about 1/12 that of the Ti–6Al–4V alloy and the wear mechanism of coating is a mixed type of slight peeling-off, adhesion and abrasion. [Copyright &y& Elsevier]

Abstract: An in situ AlTiSi ternary phase local reinforced aluminum MMCs composite was successfully fabricated by combustion synthesis and nonpressure infiltration course. XRD results show that the reinforced region of the composite is composed of Al and ternary AlTiSi phase with the composition closing to Ti(Al0.8Si0.2)3. The volume fraction of reinforcement can be controlled by adjusting Al content in compacts. SEM results show that the morphologies of the AlTiSi particles are polygonal and/or spherical. There exists some residual Ti surrounding by AlTiSi phase in the composites. In addition, there is some residual Si in the matrix in the form of Al–Si binary eutectic. The wettability between AlTiSi reinforcement and Al matrix is very good, and the reinforcement lies in the center of α-Al dendritic. [Copyright &y& Elsevier]

Abstract: The effect of Ti/C molar ratio on the SHS reaction of the Cr–Ti–C system was investigated. With the Ti/C ratio increasing, the type of products synthesized by SHS varied, and the amount of solid solution (Ti,Cr)Css increased in the final products; furthermore, also the lattice parameter of (Ti,Cr)Css increased due to the reduction in the solubility of Cr in TiC. Moreover, the combustion temperature increased, resulting in the increase of average grain size of (Ti,Cr)Css from ∼1 μm to ∼5 μm as well as the grain shape looked more and more like spherical. [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: The effect of predeformation on the α-Mg grains in the AZ91D alloys was investigated in different stages during the semisolid processing. The result showed that, with the increase of compressive ratio, the α-Mg dendrites in the as-cast microstructures gradually oriented themselves in the direction that was vertical to the compressive direction, and exhibited an obvious directional character. During the sequent heat treatment at 310°C for 20min, the recrystallization was induced in the deformed alloys by the increasingly accumulated systemic strain energy. The metallographical observation showed that the average size of recrystal α-Mg grains gradually reduced with the increase of compressive ratio. The reason might be that the nucleation to growth ratio of the renascent recrystal α-Mg grains gradually increased in the recrystallization process. Due to the recrystallization mechanism, the predeformation made the α-Mg grains particularly rounder and finer after the semisolid isothermal heat treatment at 560°C for 20min. The average diameter of the globular α-Mg grains in the semisolid microstructures also reduced with the increase of compressive ratio and this descending trend was almost similar to that in the recrystal microstructures, which further demonstrated that the recrystallization had an inevitable role on the evolution process of globular grains during SIMA process. While the compressive ratio surpassed 20%, the above descending trend was not so evident as that below 20%. In addition, the effect of predeformation on the tensile strength and elongation of the semisolid AZ91D alloys was also discussed in the present paper. [Copyright &y& Elsevier]

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]