CONSOLIDATION AND MECHANICAL-PROPERTIES OF MOSI2-BASED MATERIALS

The consolidation behaviour of MoSi2 powder, MoSi2 blended with coarse and fine niobium powder, and MoSi2 blended with SiC whiskers during h ot isostatic pressing (HIP) was studied: The HIP model, developed by A shby and coworkers, was used to guide the choice of consolidation para meters (pressure, temperature and time). Literature information, exper imental measurements and, in some cases, the rule of mixtures estimate s were used to determine material property data required as input to t he HIP model program. Samples were subjected to HIP at 207 MPa in the temperature range 1200-1400 degrees C for 1 and 4 h, to produce compac ts with minimal porosity and desirable microstructures. Density measur ements by the Archimedes principle method were compared with model pre dictions. Matrix-reinforcement interfaces and secondary phases in the materials were studied. The compacts were machined to produce specimen s for room temperature fracture toughness testing. Single-edge-notched specimens were loaded monotonically to failure in a three-point bendi ng configuration. The fracture surface morphologies were analyzed by s canning electron microscopy. Fracture mechanisms were identified and c orrelated with consolidation parameters and microstructures.