Formation of M_(n+1)AX_n phases in Ti–Cr–Al–C systems by self-propagating high-temperature synthesis

In this paper, phase composition of the Mn+1-AXnphases by self-propagating high-temperature synthesis(SHS) was determined using Ti, Cr, Al, and carbon black as raw materials. And, phase composition and microstructures of the Mn+1AXnphases-contained bulk by SHS with the pseudo-hot isostatic pressing(SHS/PHIP) were investigated in Ti–Cr–Al–C systems raw materials. Rietveld XRD refinement was introduced to study the lattice parameters and phase composition of the resultant phases from the SHSed and SHS/PHIPed samples. Ti2 AlCx,Ti3AlC2x, and Cr2 AlCxby SHS were detected in the Ti–Cr–Al–C systems, as well as the binary carbide of TiC and intermetallics. The mechanical properties of the synthesized bulk samples were determined, exhibiting a high strength and toughness compared with the typical monolithic Mn+1AXnphase ceramics. It is indicated that the samples prepared by SHS/PHIP are identified to be a strategy for improving the mechanical properties of monolithic Mn+1AXnphase.     

Synthesis of ZrC Nanoparticles in the ZrO_2–Mg–C–Fe System Through Mechanically Activated Self-Propagating High-Temperature Synthesis

ZrC nanoparticles in the matrix of Fe were produced by the mechanically activated self-propagating hightemperature method using ZrO2/C/Mg/Fe powder mixtures. The effects of milling time, Fe content, and combustion temperature as well as the formation route for synthesizing ZrC powder particles were studied. The samples were characterized by XRD, SEM, TEM, and DTA. The XRD results revealed that, after 18 h of mechanical activation, ZrO2/ZC/Mg/Fe reacted with the self-propagating combustion(SHS) mode at 870 °C producing the ZrC–Fe nanocomposite. It was also found that both mechanical activation and Fe content played key roles in the ZrC synthesis temperature. With a Fe content of(5–40) wt%, the SHS reaction proceeded favorably and both the ZrC formation temperature and the adiabatic temperature(Tad) decreased. The Mg O content was removed from the final products using a leaching test process by dissolving in hydrochloric and acetic acids.