Transformation Superplasticity of Intermetallic and Ceramic Matrix Composites
Abstract
Transformation superplasticity - defined as the capability of allotropic materials to deform rapidly and without fracture upon thermal cycling between their two phases - has been studied in a series of monolithic and composite materials systems: metals (Fe, Ti and Zr), metal matrix composites (Ti6Al4V-TiC, Ti6Al4V-TiB and Fe-TiC), intermetallic matrix composites (NiAl-ZrO2), ceramics (Bi2O3) and ceramic matrix composites (zirconia-based system). Often, samples were fabricated in house by powder processes and in all cases their microstructure was characterized before and after deformation. Tensile experiments demonstrated that samples deform more rapidly and to higher fracture strains when thermally cycled around their phase transformation than when held at a constant equivalent temperature. Furthermore, theoretical modeling was performed using both analytical closed- form solution methods and finite-element numerical methods, and good agreement with experimental data was obtained. Major transformation superplasticity milestones include: first complete study of zirconium, first demonstration in intermetallic systems (titanium aluminide and nickel aluminide), first demonstration in ceramic systems (bismuth oxide and zirconia), first numerical model (finite-element), new continuum model (at high stresses), first demonstration of whisker alignment (in Ti-6Al4V/TiB), first use of hydrogen (in Ti). Also, our collaboration with industry has resulted in a completed Phase I SBIR project as well as a subsequent Phase II project initiated in 2000 with NSF sponsorship, an important step towards commercialization of transformation superplasticity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 14, 2000
- Accession Number
- ADA384295
Entities
People
- David C. Dunand
Organizations
- Massachusetts Institute of Technology