PROCESSING, MICROSTRUCTURE, AND ELEVATED-TEMPERATURE MECHANICAL-PROPERTIES OF MOSI2 CONTAINING ER2MO3SI4 AND ER2O3 PARTICLES

[摘要] Powders of MoSi2 containing Er2Mo3Si4 and Er2O3 particles were produced by ball milling are-melted buttons of MoSi2 containing 20 vol.% Er2Mo3Si4. Two composites with grain diameters of 9 and 16 mu m were produced by hot pressing the powders to 98% of theoretical density at 1565 degrees C and 1650 degrees C respectively. Some evidence of mechanical alloying was observed, but the majority of the Er2Mo3Si4 and Er2O3 particles were situated on grain boundaries. Compressive decremental step-strain rate tests were performed in the homologous temperature range of 0.54 T-m to 0.7 T-m (1100-1400 degrees C) for strain rates ranging from 5 x 10(-4) s(-1) to 1 x 10(-6) s(-1). Nominal values for the stress exponent, n, and the activation energy for creep, Q, were determined using a constitutive equation for power-law creep. Below 1200 degrees C, creep was controlled by dislocation climb and glide mechanisms with n approximate to 4.5 and Q = 425 +/- 15 kJ mol(-1). Ar 1300 degrees C and above, the creep resistance was shown to be grain size dependent with creep resistance increasing with larger grain size.

[发布日期] 1994-12-20