Accession Number:

ADA272914

Title:

Strength and Toughness Improvement of Silicide Intermetallics by Nanophase and Microphase Reinforcements

Descriptive Note:

Final rept. 1 Apr 90-30 Apr 93,

Corporate Author:

MCDONNELL DOUGLAS AEROSPACE ST LOUIS MO

Report Date:

1993-10-01

Pagination or Media Count:

82.0

Abstract:

The HIP processing of MoSi2 and MoSi2 Nb powder, Nb wire, and Nb foil composites was optimized. The reaction between MOSi2 and Mo, W, Ta, and Nb reinforcements at 1700 deg C was examined. W, Ta, and Nb reinforcements formed complex, two layer reaction zones in contact with MoSi2. Reaction layer growth parameters were measured for Nb. Detailed HIP modeling and deformation mechanism mapping was carried out for MOSi2, MoSi2 Nb, and MoSi2 SiC. The results indicate 1400-1500 deg C to be optimal for producing 98 dense material. A sensitivity analysis was developed and demonstrated for HIP modeling of TiAl and MOSi2. Bend strengths of MoSi2, MoSi2 Nb powder, MOSi2 250 micrometer Nb wire, MoSi2 750 micrometers wire, and 200 micrometer Nb foil were measured between 20 and 1450 deg C in vacuum. Compositing with Nb significantly lowered elevated temperature strength. K1c was measured at 20 deg C for each composite and significant improvements were observed. Reinforcement morphology had a strong effect on toughness. Reinforcement morphologies listed in order of increasing potency are Nb powder, 250 micrometer Nb wire, 750 micrometer Nb wire, Nb foil. Quantitative comparison was made between theory and measurement of the toughness increase, and poor agreement was found. HIP reaction of MoSi2 and Ti powder was explored. Molybdenum disilicide, Ductile phase toughening, Fracture toughness, HIP Modeling, Deformation mechanism maps, Composites, High temperature intermetallics, HIP Reaction synthesis

Subject Categories:

  • Physical Chemistry
  • Laminates and Composite Materials
  • Manufacturing and Industrial Engineering and Control of Production Systems
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE