Thermal expansion of the W5Si3 and T2 phases of the W–Si–B system investigated by high-temperature X-ray diffraction

The coefficients of thermal expansion (CTE) of the W₅Si₃ and T₂ phases of the W–Si–B system were determined using high-temperature X-ray diffraction in the 298–1273 K temperature interval. Alloys with nominal compositions 62.5W37.5Si (at%) and 58W21Si21B (at%) were prepared from high-purity materials through arc melting followed by heat treatment at 2073 K for 12 h under argon atmosphere. The highly different thermal expansion coefficients of W₅Si₃ along the a (5.0 × 10^?6 K^?1) and c (16.3 × 10^?6 K^?1) axes lead to a high thermal expansion anisotropy (α_c/α_a ? 3.3). On the other hand, the T₂-phase exhibits similar thermal expansion coefficients along the a (6.9 × 10^?6 K^?1) and c (7.6 × 10^?6 K^?1) axes, indicating a behavior close to isotropic (α_c/α_a ? 1.1).