Elastic moduli of MoSi₂-based materials

We prepared MoSi₂, two-phase MoSi₂/Mo₅Si₃, and (Mo, W)Si₂ solid-solution alloy powders by mechanically alloying mixtures of elemental molybdenum, silicon, and tungsten. These powders were consolidated by hot-pressing them at 1500 °C in graphite dies. We measured the elastic moduli of these alloys by a recently developed technique for non-contact ultrasonic spectroscopy. Second-phase Mo₅Si₃ additions to MoSi₂ result in decreased values for G and E, whereas alloying MoSi₂ with WSi₂ results in increased values for G and E. An analysis of these Young's moduli and of data from the literature for various intermetallic alloys suggests that for any given alloy system, the Young's moduli for its various intermetallics as a function of density fall on a straight line. Further, the lines for the different alloy systems are approximately parallel.