Thermal expansion of the V@@d5@Si@@d3@ and T@@d2@ phases of the V-Si-B system investigated by high- temperature X-ray diffraction

• Published in: Intermetallics Vol. 17; no. 10; pp. 792 - 795
• Main Authors: Rodrigues, Geovani, Nunes, Carlos Angelo, Suzuki, Paulo Atsushi, Coelho, Gilberto Carvalho
• Format: Journal Article
• Language: English
• Published: 01.10.2009
• ISSN: 0966-9795
• DOI: 10.1016/j.intermet.2009.03.006

The thermal expansion anisotropy of the V@@d5@Si@@d3@ and T@@d2@-phase of the V-Si-B system were determined by high-temperature X-ray diffraction from 298 to 1273 K. Alloys with nominal compositions V@@d62.5@Si@@d37.5@ (V@@d5@Si@@d3@ phase) and V@@d63@Si@@d12@B@@d25@ (T@@d2@-phase) were prepared from high- purity materials through arc-melting followed by heat-treatment at 1873 K by 24 h, under argon atmosphere. The V@@d5@Si@@d3@ phase exhibits thermal expansion anisotropy equals to 1.3, with thermal expansion coefficients along the @@ia@ and @@ic@-axis equal to 9.3 x 10@@u-6@ K@@u-1@ and 11.7 x 10@@u-6@ K@@u-1@, respectively. Similarly, the thermal expansion anisotropy value of the T@@d2@-phase is 0.9 with thermal expansion coefficients equal to 8.8 x 10@@u-6@ K@@u-1@ and 8.3 x 10@@u-6@ K@@u-1@, along the @@ia@ and @@ic@-axis respectively. Compared to other isostructural silicides of the 5:3 type and the Ti@@d5@Si@@d3@ phase, the V@@d5@Si@@d3@ phase presents lower thermal expansion anisotropy. The T@@d2@-phase present in the V-Si-B system exhibits low thermal expansion anisotropy, as the T@@d2@-phase of the Mo-Si-B, Nb-Si-B and W- Si-B systems.