Mo-Si-B三元系中T2相合金制备及其室温力学性能

通过放电等离子烧结(SPS)制备T2(Mo5SiB2)相合金,并采用SEM、XRD及压痕、压缩和三点弯曲等实验对合金的微观组织和室温力学性能进行表征。结果表明:SPS法以独特的等离子活化烧结方式制备出纯度高、致密且晶粒细小的T2相合金。该合金在室温压缩下几乎没有塑性变形,抗压强度为2907MPa;维氏硬度为17.86GPa,压痕法测得的断裂韧性为3.23MPa·m1/2,与三点弯曲法测得的3.34MPa·m1/2接近,沿{001}面发生解理断裂。共价键交替排列,是T2相室温脆性、高强度、高硬度的根本原因。

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·m1/2, similar to the averaged value of 3.34 MPa·m1/2 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