Preparation and Room Temperature Mechanical Properties of T2 Alloy in the Mo-Si-B System

The intermetallic T2 (Mo5SiB8) alloy was prepared by sparking plasma sintering (SPS). The microstructure and room temperature mechanical properties were characterized by SEM, XRD as well as indentation, compression and notched three-point bending tests. The results show that SPS, a unique plasma activation sintering approach, favors the formation of pure T2 alloy with a dense and fine-grained microstructure. Almost no plastic deformation is observed in the true strain-stress curve of the T2 alloy after room temperature compression and the alloy has a compressive strength of 2907 MPa. The Vickers hardness is 17.86 GPa, while the averaged fracture toughness determined from indentation crack lengths is 3.23 MPa.m(1/2), similar to the averaged value of 3.34 MPa.m(1/2) from single edge notch bend specimens. The cleavage fracture occurs across {001} planes of the T2 alloy in the three-point bending tests at room temperature. For the T2 alloy, the contribution to room temperature brittleness, high strength and high hardness is mainly derived from the covalent bonds which arrange alternately in the T2 phase.