Processing, Microstructure, and Elevated Temperature Mechanical Properties of MoSi₂ Containing Er₂Mo₃Si4 and Er₂O₃ Particles


Powders of MoSi2 containing Er2Mo3Si4 and Er2O3 particles were produced by abll milling rice-melted buttons of MoSi2 containing 20 vol.% Er2Mo3Si4. Two composites with grain diameters of 9 and 16 μm were produced by hot pressing the powders to 98% of theoretical density at 1565 °C and 1650 °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 Tm to 0.7 Tm (1100-1400 °C) for strain rates ranging from 5 × 10-4 s-1 to 1 × 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 °C, creep was controlled by dislocation climb and glide mechanisms with n ≈ 4.5 and Q 425 ± 15 kJ mol-1. At 1300 °C and above, the creep resistance was shown to be grain size dependent with creep resistance increasing with larger grain size. © 1994.


Materials Science and Engineering

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© 1994 Elsevier, All rights reserved.