Nanosized TiCu powders were synthesized by high energy ball milling of micron-sized Ti and Cu powders. Dense TiCu could be consolidated by high frequency induction sintering method within 1 min using both horizontally milled elemental powders of Ti+Cu and mechanically synthesized powders of TiCu. The consolidation was accomplished under the combined effect of induced current and applied mechanical pressure. The grain size, sintering behavior and hardness of TiCu sintered from both powders were examined.
Nanopowder of Fe 2 O 3 , Al, Cr and Si was fabricated by high energy ball milling. A dense nanostuctured A 2 O 3 and 6.06Fe 0.33 Cr 0.16 Al 0.23 Si 0.29 composite was simultaneously synthesized and consolidated using high frequency induction heated sintering method within 1 minute from mechanically activated powders of Fe 2 O 3 , Al, Cr and Si. The grain sizes of Al 2 O 3 and Fe 0.33 Cr 0.16 Al 0.23 Si 0.29 in composite are 80 and 18 nm, respectively.
We previously reported that the electrical explosion of Cr-plated Ti wires in N 2 gas produced nanoparticles composed of cube-shaped TiN, sphere-shaped Cr 2 N and extremely fine (Ti,Cr)N particles. In this study, the mixture powders were consolidated by pulsed current activated sintering (PCAS). A near-full density compact could be obtained within five minutes at 1600°C. The shrinkage-time profile revealed an abnormally high contraction of the compact at 1500°C after the typical sintering period observed at temperatures between 700 to 1300°C. The sudden shrinkage at 1500°C turned out to be the consequence of the eutectic melting of Cr 2 N particles which decomposed to Cr and N 2 . The metallic Cr phase was located mostly at triple points and grain boundaries prohibiting the grain growth of TiN grains. The microhardness of the compact (13.6 GPa) was lower than that of pure TiN compact (16.2 GPa) due to the soft Cr phase. Nevertheless, the fracture toughness of the compact (6.6 MPa·m 1/2 ) was higher than that of the pure TiN compact (6.0 MPa·m 1/2 ) probably because the metallic Cr along grain boundary may deter the crack propagation.
In the case of cemented TiCN, Ni or Co is added as a binder for the formation of composite structures. However, the high cost of Ni or Co and the low corrosion resistance of the TiCNNi cermet have generated interest in recent years for alternative binder phases. In this study, TiAl was used as a binder and consolidated by the high-frequency induction heated sintering (HFIHS) method. Highly dense TiCNTiAl with a relative density of up to 100% was obtained within 2 min by HFIHS under a pressure of 80 MPa. The method was found to enable not only the rapid densification but also the inhibition of grain growth preserving the nano-scale microstructure. The average grain sizes of the sintered TiCN and TiCNTiAl were lower than 100 nm. The addition of TiAl to TiCN enhanced the hardness and toughness due to increase of relative density.
Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. Attention has been directed to the application of nanomaterials as they possess high strength, high hardness and excellent ductility and toughness. A one-step synthesis and consolidation of nanostructured Mg 0.6 Al 0.8 Ti 1.6 O 5 was achieved by pulsed current activated heating using the stoichometric mixture of MgO, Al 2 O 3 and TiO 2 powders. Before sintering, the powder mixture was high-energy ball milled for 10 h. From the milled nanopowder mixture, a highly dense nanostructured Mg 0.6 Al 0.8 Ti 1.6 O 5 compound could be obtained within one minute under the simultaneous application of 80 MPa pressure and an pulsed current. The advantage of this process is that it allows an instant densification to the near theoretical density while sustaining the nanosized microstructure of raw powders. The sintering behavior, microstructure and mechanical properties of Mg 0.6 Al 0.8 Ti 1.6 O 5 were evaluated.
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