OVERVIEW

1. Determination of Creep Mechanisms and Modeling Low Temperature Creep of Two-Phase Titanium AlloysSreeramamurthy Ankem, University of Maryland, College Park, DMR 0906994 INTELLECTUAL MERIT OVERVIEW Titanium alloys have many applications including aerospace, naval, biomedical, and nuclear. Often, titanium components are subject to loading for long periods of time at low temperatures. Titanium has long been known to creep, i.e.: time-dependent permanent deformation, at low temperatures. Therefore, it is important to understand the mechanisms of creep deformation to predict the mechanical reliability of the structures and to design advanced materials with improved creep resistance. (a) (b) APPROACH Mechanical Testing, TEM & SEM Microscopy, Crystallographic Modeling, FEM modeling, and Modeling of deformation mechanisms based on thermodynamics, kinetics and mechanics of materials principles. RESULTS Previously the PI has shown that twinning is a major mechanism in creep deformation of an alpha Ti-1.6V alloy. In this part of the investigation the effect of strain rate on twinning was studied. It was found that the twin density increases with strain rate but the twin thickness decreases with strain rate as shown. A decrease in twin thickness can be explained based on the recent theories by the PI and his co-investigators where they have shown that twin growth is controlled by the diffusion of oxygen. The effect of strain rate on (a) twin density and (b) twin thickness on α Ti-1.6V alloy at room temperature strained to 3%.

2. Determination of Creep Mechanisms and Modeling Low Temperature Creep of Two-Phase Titanium Alloys Sreeramamurthy Ankem, University of Maryland, College Park, DMR 0906994 BROADER IMPACTS Teaching, training, and outreach will be an integral part of the investigation. The undergraduate and graduate students will learn research, analytical, and communication skills by working in the laboratory and contributing to papers and presentations. The PI has an excellent track record in supporting under-represented minorities and undergraduate students. EDUCATION A graduate student, Mr. Zane Wyatt is involved with this project. In addition, two undergraduate students, Mr. Alexander Kao and Ms. Ninoska Moratin (a minority student), were also involved with this project during the summer of 2009. OUTREACH The findings of this investigation are scheduled to be presented at various national and international conferences in the near future. In addition, research papers based on these results will be submitted to various journals for publication. The PI interacts with undergraduate and graduate students as the founding and current faculty advisor for the Materials Advantage Student Chapter at the University of Maryland, College Park. This chapter has received many awards from the national chapter of TMS/ASM, including Chapter of Excellence Awards and just this year, won the “Membership Challenge-Most Students Recruited” Award. Through this chapter the students are very active in participating at various national conferences of the ASM and TMS professional societies.