Mechanical properties of Mo5SiB2 single crystals

Mo5SiB2 is a new refractory metal silicide with great potential for ultra-high temperature structural applications. We succeeded to grow high purity single crystals of Mo5SiB2 using an optical floating zone method. Single-crystal elastic constants at room temperature (RT) of the silicide were measured. Mo5SiB2. has less anisotropic single crystal elastic moduli and a lower shear modulus and a lower Debye temperature than MoSi2. Mo5SiB2, has a slightly higher bulk, shear. Young's moduli and Debye temperature than Mo5Si3, Mo5SiB3, has a RT Vickers hardness of around 18 GPa, which is much larger than those of Mo5Si3 and MoSi2 Fracture toughness around 2 Mparootm is comparable to those of Mo5Si3 and MoSi2. Compression tests were performed at 1500 degreesC. Slip was observed on [001](010) for [021] orientation. However, slip on <100>(001), which has been reported to be activated, was not observed. Mechanical properties of Mo5SiB2 single crystals are discussed in relation to the complex crystal structure of Mo5SiB2. (C) 2002 Elsevier Science B.V. All rights reserved.