Fundamental Investigations of Impurity Effects in alpha-Titanium
Abstract
Funds are provided to investigate and model the effects of oxygen, aluminum, and other alloying elements on the deformation behavior of titanium.This project addresses directly the PE 0601153N objectives for furthering basic research efforts including scientific study and experimentation directed toward increasing knowledge and understanding in national security related aspects of physical, engineering, environmental, and life sciences. The research described in this proposal will integrate state-of-the-art experimental and computational approaches to understand the effects of O interstitial and Al substitutional solutes on dislocation-mediated deformation of a-Ti-Al-O alloys. A primary focus of the work is to understand the microscopic origins of planar-slip behavior observed in a-Ti(O) and a-Ti(Al) systems. Our prior work, suggests that the mechanisms underlying this effect in these two systems is likely to be different, with SRO playing an important role in a-Ti(Al) and oxygen interstitial shuffling being important for a-Ti(O). The proposed experimental work will develop a more quantitative understanding of planar slip behavior, through studies of deformation microstructures in a-Ti-Al-O alloys deformed under varying strain rates and temperatures. This experimental work will exploit novel electron microscopy techniques that enable characterization of the state of chemical SRO, residual strains, and the thickness of planar slip bands. Computational work will aim to use atomistic and quantum mechanical DFT calculations to understand the connection between solute content, dislocation core configurations, and elementary processes of dislocation slip and cross-slip. The results of these calculations will be used in mesoscale models to explore planar versus wavy slip behavior, for direct comparisons with the experimental observations. Through this integrated approach our aim is to identify the mechanisms underlying the formation of planar slip bands and how they can be mitigated through alloy design strategies, such as selective introduction of substitutional solute alloying additions. The formation of planar slip bands has been reported in the literature to correlate with decreases in toughness and fatigue strength, and increased susceptibility to stress-corrosion cracking. Thus, our work aimed at designing alloys that are less prone to form these slip bands holds the promise of designing a-Ti alloys that are less susceptible to the enhancement of such failure processes by small changes in oxygen-interstitial content.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912376
Entities
People
- Mark Asta
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents