1. CAREER: The Stability and Influence of Metastable Retained Austenite During Fatigue of Advanced Steel Alloys Kip Findley, Colorado School of Mines, DMR 0955236 Advanced Steel Products and Processing Research Center Project Overview: Metastable metal alloys that take advantage of stress or strain induced microstructural changes are being implemented more widely in transportation and medical industries. However, there are several fundamental factors associated with fatigue loading of these alloys that could have major implications on their service in structural applications. Microstructures of TRIP steels. The green phase, retained austenite, transforms to a harder phase, martensite, during deformation, which changes the material mechanical properties. The amount of the transformation depends on size, morphology, location, and composition of retained austenite. Objectives: Characterize changes in microstructure during loading that affect fatigue performance of transformation induced plasticity (TRIP) steels. Develop models to predict the fatigue performance based on microscale changes in the structure. Advanced high strength steels, such as TRIP steels, are used in formed components in automobiles. The effects of pre-straining, meant to simulate forming strains, were assessed by pre-straining the alloys at room temperature and -20 °C followed by fatigue testing at room temperature. Pre-straining also transforms some of the austenite into martensite. The amount that is transformed is dependent on the amount of pre-strain and deformation temperature The fatigue results indicate that the fatigue response is independent of the pre-strain level. It is hypothesized that the fatigue behavior is controlled by the weakest phase in the microstructure, which is not significantly affected by austenite to martensite transformation during pre-straining.

2. CAREER: The Stability and Influence of Metastable Retained Austenite During Fatigue of Advanced Steel Alloys – Broader Impacts Kip Findley, Colorado School of Mines, DMR 0955236 Advanced Steel Products and Processing Research Center Broader Impacts The project team presented their work to sponsors of the Advanced Steel Processing and Products Research Center (ASPPRC), who is also supporting this work. The work has been presented at semi-annual meetings and visits to several sponsor companies. AK Steel and ArcelorMittal have enabled portions of this work by providing alloys and producing experimental heats of material. These interactions have provided the opportunity for the work to be validated and disseminated in a steel research community that includes users and producers of steel. An undergraduate laboratory module that explores stress and strain induced phase transformations for materials used in biomedical and automotive applications was improved through the insight gained from the research. Hydraulic grips, purchased through the grant, were implemented to improve the efficiency and data quality of a fatigue laboratory module. A middle school science teacher was hired (picture at right with PI) to develop elementary and middle school laboratories that demonstrate materials fundamentals and engineering design concepts. The modules were introduced to elementary school teachers at a workshop in the Bechtel K-5 Education Excellence Initiative program. The teacher will use one module in the fall of 2014 for her science course. The PI utiliized laboratory modules developed in previous years of the program at an outreach event for a STEM middle school that serves many students from underrepresented groups (pictures at right). The modules involved tensile and toughness testing. The Colorado School of Mines student Material Advantage Chapter cooperated on the outreach activity. Several undergraduate researchers, both from CSM and other institutions, have been hired to perform independent research projects within the program.