Effect of Alloying and Thermo-Mechanical Processing on the Deformation of Hexagonal Close-Packed Alloys

North Carolina State University, Raleigh NC

Investigators

Abstract

Hexagonal close-packed (HCP) metals such as titanium, magnesium and zirconium alloys are commonly used for structural applications in energy, transportation and biomedical technologies, and a thorough understanding of their mechanical integrity is central for their in-service sustainability. Correlating fine-scale structure of the alloys with their resistance to deformation at service temperatures will allow for new understanding of the mechanisms that control alloy performance, and can provide guidance for design of high-strength, durable components. This award supports fundamental scientific research to understand the role of alloy composition and structure on mechanical properties in zirconium-based alloys. The research brings experimental testing together with computational modeling to predict the behavior of these alloys based on the new knowledge of their composition, structure, and how these relate to properties and performance in service. The work will lead to new scientific understanding that can be applied to a number of important alloy systems, and will provide excellent educational opportunities for students participating in the research. Particular emphasis is placed on broadening participation in scientific research through engagement in K-12 outreach programs which will allow high school students the opportunity to participate in the research, along with undergraduate and graduate students. This research addresses the influence of thermo-mechanical treatment and alloying on creep anisotropy of zirconium alloys with emphasis on niobium addition and heat treatment. The addition of niobium as an alloying element has been shown to lend better performance and durability, and this research aims to understand the phenomena controlling this behavior. Creep anisotropies in these alloys will be investigated in the different regimes such as power-law and viscous creep, as well as at high stresses in the power-law breakdown region. Corresponding deformation microstructures will be characterized for a thorough understanding of the underlying creep mechanisms and the biaxial creep anisotropy. The knowledge derived from this research can be applied to understand the plastic deformation mechanisms of other HCP alloys at high temperatures, and can provide robust tools to predict dimensional changes in service. This research involves both experimental and modeling approaches, and the findings will be integrated into classroom teaching for training the next generation of Engineers.