Determination of Creep Mechanisms and Modeling Low Temperature(<0.25Tm) Creep of Two-Phase Titanium Alloys

University Of Maryland, College Park, College Park MD

Investigators

Abstract

TECHNICAL SUMMARY: Two-phase alloys in general and &#945;-&#946; titanium alloys in particular are technologically important. The attractive properties of titanium alloys include high strength to weight ratio, excellent corrosion resistance and biocompatibility. For these reasons, they are used in a number of high technology areas. In many of these applications, components are subjected to constant loads over extended periods of time at low temperatures (<0.25Tm). Recently, many unexpected results have been reported which are of great importance in designing and in selecting titanium alloys for various applications. For example, it has been shown that twinning, which has traditionally been known to be a very fast deformation mechanism, can occur very slowly. Further, due to twinning, the single-phase &#945; and &#946; titanium alloys can creep (i.e. plastically deform) at low temperatures. It was also found that the deformation mechanisms of the two-phase &#945;-&#946; titanium alloys can be quite different than those of the single phase alloys due to interactions between phases. The exact reasons for this behavior are not known. The aim of this investigation is to systematically study the low temperature creep of &#945;-&#946; titanium alloys as a function of volume fraction and morphology of &#945; and &#946; phases; using three different Ti-V alloys as the model systems. Crystallographic modeling as well as three-dimensional anisotropic finite element modeling will be used to determine the interactions between phases. Scanning electron microscopy and transmission electron microscopy will be used to determine the deformation mechanisms. Based on these results, optimal microstructures for improved low temperature creep resistance will be identified. NON-TECHNICAL SUMMARY: In a number of applications, loads are applied on structural members at low temperatures such as room temperature. At times, loads are applied on these structures over extended periods of time, which can result in time-dependent deformation, i.e. creep. This investigation focuses on determining optimal chemistry and microstructures of two-phase structural materials such as titanium alloys for low temperature creep resistance. The results will be widely publicized through participation in various technical conferences and publication in reputed journals. While this study of low temperature creep deformation is based on two-phase titanium alloys, the results are expected to contribute to the wide field of composite materials in general. During this investigation, graduate students will be trained in advanced modeling and experimental techniques. These graduate students will then go on to take up technical positions in industry, government, or education. In addition to participation in various national and international conferences, this project also promotes outreach to the community and diversity through such activities as the Materials Advantage Student Chapter. The Principal Investigator is the founding faculty advisor for the University of Maryland, College Park Materials Advantage Student Chapter. This chapter actively participates in open-houses at the University to educate the public on materials science. Further, this chapter encourages both undergraduate and graduate students to participate in the various national professional society meetings.