PRET: A University-Industry Partnership Research and Transition of Gamnma Titanium Aluminides
Abstract
Cooling rates during casting have been shown to significantly influence yield strength, for the processing related research, tensile ductility and property variability in three different TiA1 alloys. Variations in ductility are most sensitive to extrinsic defects such as porosity or the presence of large grains oriented for easy straining. A technique for quantitative analysis of surface connected porosity has been developed. Additionally, in the area of induction skull melting, fundamental information on the kinetics of aluminum vaporization has been established. Important differences in melt superheat and skull weight have been observed after casting in different melt atmospheres. A comprehensive study of the effect of preheat, stress-relief temperature, Al level and postweld heat treatment on the structure and properties of electron beam welds has also been completed. For deformation-related work, it has been found that the local plastic strain to failure increases significantly as the volume of plastically strained materials decreases based on the testing of notched and unnotched specimens. Moreover, plastic strain capabilities of even 0.8% have been found sufficient to blunt elastic stress concentrations up to Kt = 2.3. Strain mapping procedures developed in this program demonstrate that crack initiation is associated with groups of grains with intense plastic straining.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1999
- Accession Number
- ADA397432
Entities
People
- Paul S. Steif
- Tresa M. Pollock
Organizations
- Carnegie Institute of Technology