K. Linga Murty, North Carolina State University DMR 0412583

1. Effect Of Alloying And Heat Treatment On The Biaxial Creep Behavior Of Titanium Alloys K. Linga Murty, North Carolina State University DMR 0412583 • The main objectives of this project are to a) study the effect of alloying and heat treatment on the mechanical and creep anisotropy of Ti alloys, b) investigate the effect of biaxial loading on creep characteristics, c) investigate deformation microstructures with particular emphasis on dislocation substructure formation during creep, and d) develop microstructure-based creep constitutive equations. • Creep tests performed under uniaxial loading on Ti32.5 revealed subgrain formation at lower stresses and random distribution at high stresses (Fig-top) very similar to those on hoop creep in this alloy under biaxial loading (Fig-bottom). • Creep studies to-date on cp-Ti sheet revealed grain boundary sliding (GBS) at low stresses with the characteristic n=2 and the activation energy for grain boundary diffusion while dislocation climb was identified at higher stresses. These results are similar to those reported earlier on hoop creep Ti32.5 alloy under biaxial loading (Fig-bottom). • A threshold stress based model was developed to explain creep of nanocrystalline materials that agreed with experimental results of impression creep on nc-aluminum (23nm) processed through high precision torsion of compacted ball-milled powders (S. Gollapudi et al, MSE, A527, 2010, pp.5773-5781). 243MPa 352MPa

2. Summer 2008 Summer 2009 Effect Of Alloying And Heat Treatment On The Biaxial Creep Behavior Of Titanium Alloys K. Linga Murty, North Carolina State University DMR 041258# Summer 2010 High with grad student, PI and an REU