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The binary tetragonal intermetallic compound Mo5Si3 has significant thermal expansion anisotropy (TEA) with the coefficient of thermal expansion (CTE) of the c-axis (αc) more than double that of the a-axis (αa). Since boron has been shown to improve the oxidation stability of alloys near this composition, we explore the effect of adding boron on the thermal expansion anisotropy of Mo5+ySi3−yBx (T1) and subsequently the adjoining phases in thermal equilibrium. Powder X-ray diffraction was conducted at high temperatures using high energy (>40 keV) synchrotron X-rays. All of the intermetallics in this system (Mo5SiB2, MoSi2, MoB and Mo3Si) have moderate CTE values ranging from 7.17 ppm/°C for the cubic Mo3Si to nearly 14 ppm/°C for the c-axis of Mo5Si3B. The nearly isotropic TEA for Mo5B2Si was confirmed. The variability of the TEA of Mo5Si3B from 1.83 to 2.43 is explained in terms of the site occupancy and the change of the inter-atomic spacing of the Mo atom chains along the c-axis. [Copyright &y& Elsevier]

Abstract: The pure NiAl intermetallic compound was fabricated by the combustion synthesis and hot pressing technique. Microstructure examination showed that the NiAl intermetallic compound contained fine grains. Analysis of the X-ray diffraction and the HRTEM studies showed that the phase in the intermetallics was the only NiAl phase. The NiAl showed prominent compression properties. The true ultimate compression strength and the fracture strain of the NiAl are 1002−94 +72 MPa and 21.6−1.8 +1.8%, respectively. The work-hardening capacity (H c) is 1.40−0.07 +0.09 and the Vickers micro-hardness is 360−19 +15 HV. The finer grains, the high density dislocation and the seriously distorted lattices in the matrix, and the intense interactions between dislocations contribute to the prominent compression properties. [Copyright &y& Elsevier]