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Tungsten carbide (WC) particle reinforced Ni3Al intermetallic matrix composites (WC–Ni3Al) was first fabricated by in situ thermite reaction. The microstructure and high temperature wear resistance of the WC-Ni3Al composite have been studied. The WC-Ni3Al composite contains Ni3Al, WC and B2 phases, and the volume fraction of Ni3Al, WC and B2 were 55.27%, 10.67% and 34.06%, respectively. The WC-Ni3Al composite exhibits excellent friction and wear resistance. Our findings have important engineering implications for the preparation of intermetallic matrix composites.

Intermetallic compounds (NiAl) are potential high-temperature structure materials due to their exceptional physical and thermo-mechanical properties. NiAl offer a wide range of applications which stem from aerospace to automobile industry but their utilization is restricted owing to low ductility and fracture toughness. However, carbon nanotubes (CNTs) have been recognized to impact strength and improve mechanical properties in metal matrices because of their superior tensile strength, high aspect ratio, low density, and elastic modulus. This has contributed to advance developments of novel materials. In recent times, CNTs have been a focus of immense research due to presence of sp2 C–C bonds in their outer shells, with continuous cylindrical shape which significantly contributed to their superior characteristics. The processing methods of integrating CNTs in metal matrices as well as maintaining their structural integrity through the powder metallurgy routes are reviewed. The mechanical properties, microstructure evolutions, effect of CNT addition, and sintering mechanism are also articulated in this review. [ABSTRACT FROM AUTHOR]

Intermetallic matrix composites reinforced with ceramic particles have received a great deal of attention. Iron aluminide is known to be a good material for the matrix in such composites. Two processes were used to fabricate FeAl-TiB2 intermetallic matrix composites. One was liquid melt in-situ mixing, and the other was arc melting and suction casting processes. FeAl-TiB2 IMCs obtained by two different methods were investigated to elucidate the influence of TiB2 content. In both methods, the grain size in the FeAl alloy decreased with the presence of titanium diboride. The grain size of in-situFeAl-TiB2 IMCs became smaller than that of arc FeAl-TiB2 IMCs. Significant increase in fracture stress and hardness was achieved in the composites. The in-situ process gives clean, contamination-free matrix/reinforcement interface which maintained good bonding causing high load bearing capability. This contributed to the increase in the mechanical properties of composites. [ABSTRACT FROM AUTHOR]

Densification behavior of sub micron tungsten carbide composites based on boron doped Fe60Al40 and Ni3Al binders were investigated. Soft cobalt binder phase in WC hard metals was replaced by harder and tougher Fe60Al40 and Ni3Al intermetallics with boron level up to 0.1wt%. Intermetallic binders were prepared in ultrafine form under controlled atmosphere using ring grinding, blended with sub micron WC powder and then uniaxilly hot pressed under 20 MPa pressure in argon atmosphere for 4 minutes duration at temperatures of 1450 °C, 1500 °C and 1550 °C. It was found that the density of composites increased significantly and WC grain size increased slightly with increase in sintering temperature. The composites exhibited highest density (about 99.5 %TD) and minimal grain growth in WC at sintering temperature of 1500 °C. The presence of boron was found to facilitate densification during liquid phase sintering and boron also resulted in achieving uniform microstructure with continuous binder phase, nearly full density and high faceted features in the structure. [ABSTRACT FROM AUTHOR]

B2–NiTi and Ti3Al based single and dual phase intermetallic matrix composites (IMC) with TiC reinforcement were laser alloyed using Ni/Al–VC, Al–VC and Al–Cr3C2 powder mixtures. A sufficient amount of Ti from the substrate reacted with the injected alloy powder mixture to form Ti based intermetallics and TiC. The coatings were characterised by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and energy dispersive spectroscopy (EDS). The erosion resistance of the alloyed layers was characterised by high speed particle laden liquid impact erosion tests. The high work hardening ability of Ti3Al IMC strengthened by TiC reinforcement improved the erosion resistance up to a factor of 139. Compared to the single phase IMC, the dual phase IMC coatings were found not to be suitable for applications similar to the present test conditions due to possibly preferential removal of secondary precipitates. An attempt has been made to identify the influence of different depth sensing indentation (DSI) derived mechanical properties to the erosion resistance of the alloyed layers. The correlation indicates the combined contribution of hardness, strain hardening exponent, surface elasticity and yield strength on improving the erosion resistance. [ABSTRACT FROM AUTHOR]

γ-TiAl and α2-Ti3Al intermetallic matrix composites (IMC) with TiC reinforcement was laser alloyed on a Ti-6AI-4V substrate. Two different starting powder mixtures based on Al-VC and Al-Cr3C2 was used to improve the toughness and ductility of the matrix. In one of the powder mixtures, AI-VC, the laser process parameters were varied to produce γ-TiAl /α2-Ti3Al and α2-Ti3Al matrix in the surface of Ti-6AI-4V. The coatings were characterised by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and energy-dispersive spectroscopy (EDS). The cross-sectional microhardness of the tested specimens was measured before and after cavitation to identify any work hardening. In a vibratory cavitation erosion test the alloyed layer, which contains predominantly α2-Ti3Al in the matrix showed an improved erosion resistance by a factor of up to 5.2. Preferential removal of more brittle y-TiAl in the multi-phase γ-TiAl/α2→Ti3Al IMC coating is believed to have a destructive influence on the coating performance. Over the range of process parameters investigated, an improvement in hardness favours a high erosion resistance. All alloyed layers failed by brittle fracture with varying severity. [ABSTRACT FROM AUTHOR]

Abstract: Fe3Al-based composites reinforced with micron-sized titanium carbide, tetragonal zirconia and nano-scaled alumina particles were hot-pressed, and the room temperature mechanical properties were investigated. Results show that nano-Al2O3 is not an efficient ceramic for the enhancement of mechanical properties of Fe3Al, primarily due to its inhomogeneous distribution and severe agglomeration within the matrix as well as the weak interfacial bonding. By contrast, Fe3Al/5 wt.% ZrO2 composite had a strength as high as 1361 MPa and a fracture toughness of 19.0 MPa . The enhancing effect is attributed to the low thermal expansion mismatch between ZrO2 and Fe3Al matrix, and to the stress-induced transformation of ZrO2 particles. The flexural strength and fracture toughness for Fe3Al/10 wt.% TiC composite was 1086 and 20.0 MPa , respectively. The mechanical properties of Fe3Al/TiC composites decreased with TiC content above 10 wt.% due to the suppression of plastic deformation, residual porosity and interfacial debonding. [Copyright &y& Elsevier]

TiC-20 wt% NiAl and TiC-40 wt% NiAl composite materials were produced by self-propagating high-temperature synthesis (SHS) and hot isostatic pressing (HIP). In the SHS method the reacted powders were compacted by uniaxial pressing immediately after the reaction. The microstructure of the materials produced by SHS consisted of spherical carbides embedded in the NiAl matrix, whereas the microstructure of the materials produced by HIPing was more irregular. A maximum hardness of 2010 HV was measured for the material produced by HIP and a maximum fracture toughness of 10.5 MPa m was measured for materials produced by SHS. High-temperature resistance was investigated by exposing the materials to 800°C in air for 110 h. The results obtained showed that the TiC + NiAl composite materials can be recommended for use in environments consisting of oxidizing atmosphere at temperatures around 800°C where high wear resistance is required. [ABSTRACT FROM AUTHOR]

This paper presents a numerical and experimental analysis of manufacturing of intermetallic ceramic composites by powder metallurgy techniques. The scope of the paper includes the formulation and development of an original numerical model of powder metallurgy of two-phase material within the framework of the discrete element method, simulations of powder metallurgy processes for different combinations of process parameters, and a verification of the numerical model based on own experimental results. Intermetallic-based composite NiAl–Al 2 O 3 has been selected as representative material for experimental and numerical studies in this investigation. Special emphasis was given to the interactions between the intermetallic and ceramic particles by formulating the special model for adhesive contact bond. In order to properly represent a real microstructure of a two-phase sintered body, a discrete element specimen was generated using a special algorithm. Numerical validation showed the correct numerical representation of a sintered two-phase composite specimen. Finally, micromechanical analysis was performed to explain the macroscopic behavior of the sintered sample. The evolution of the coordination number, a number of equilibrium contacts, and the distribution of the cohesive neck size with respect to time are presented. [ABSTRACT FROM AUTHOR]