The influence of temperature on strength: are concentrated BCC alloys different than elements and dilute alloys? (06/12/22)
Speaker and Affliation:
Dr Daniel B. Miracle
Senior Scientist,
Materials and Manufacturing Directorate
Air Force Research Laboratory
Wright-Patterson AFB, OH 45324
When?
06th December, 2022 (Tuesday), 11:30 AM (India Standard Time)
Venue
KPA Auditorium, Department of Materials Engineering
Abstract
The influence of temperature on strength in BCC metals and alloys is not simple. Thermally-dependent regions are seen at both low and high temperatures where strength drops quickly with increasing temperature, and an intermediate plateau region is usually seen between them where strength is relatively insensitive to temperature. Together, the complex (three or more principal elements) and concentrated (principal elements of at least 5-10 at. % each) nature of refractory complex, concentrated alloys (RCCAs) may introduce important differences in deformation and strengthening mechanisms compared to BCC elements and dilute BCC alloys. For example, the relative mobility of screw and edge dislocations may be much different in some RCCAs compared to traditional BCC materials, and new models have been needed to accurately predict strength. Early datasets were insufficient to scope the thermal dependence of strength in RCCAs broadly as a class of materials, but increasing availability of data now make such a study feasible. The objective of this work is to answer the question, “is the temperature dependence of strength similar or different for RCCAs as a class of materials compared to BCC elements and conventional, dilute BCC alloys?” To answer this question, we evaluate strength vs. temperature by curating and analyzing a large dataset of results collected from the literature. This dataset includes stress vs temperature for 68 distinct RCCAs, six refractory elements, and six conventional (usually dilute) refractory alloys. Both single-phase and multi-phase RCCAs are included in the dataset and are analyzed separately. We evaluate the transition temperatures between the thermally-dependent and plateau regimes for RCCAs and compare to refractory elements and commercial alloys. The rate at which stress degrades with temperature is also evaluated, especially within the intermediate temperature regime. From this work, general features and trends for the temperature-dependent strength of RCCAs are established and described.