Seminar of Zhouwen Zhao from Michigan State University, entitle “Critical Resolved Shear Stresses (CRSS) of Hexagonal Titanium from Nanoindentation Optimization” – July 18th at 1:00 pm, in the Seminar Room


Titanium and its alloys are important engineering materials due to their low density, high strength, and good bio-compatibility. The study of critical resolved shear stress (CRSS) values of basal, prismatic, and pyramidal ⟨c + a⟩ slip systems has been a hot topic in the community as they form the basis of the description of crystal plasticity in such alloys. Experimental quantification of individual CRSS value by exclusive activation (conditions of single slip) is very difficult. An inverse methodology to establish CRSS values is through fitting simulated results to experimental counterparts. However, disagreement among CRSS ratios for commercially pure titanium by fitting against different experimental observations at room temperature has been reported [1]. It is also known that temperature and composition could alter the CRSS values or their relative order. This study aims at investigating the influence of temperature and composition on CRSS values in hexagonal titanium, that is to say, to identify parameter sets at ambient and higher temperatures for commercially pure titanium, Ti-3Al-2.5V, and Ti-6Al-4V using an efficient approach that is based on surface topography and load-displacement curve from nanoindentation. Quantitative assessment of possible sources that contribute to the deviation between simulated (using optimized parameters) and measured response from nanoindentation is carried out, such that sensitivity of the approach is established.

[1] H. Li, D. E. Mason, T. R. Bieler, C. J. Boehlert, and M. A. Crimp. Methodology for estimating the critical resolved shear stress ratios of α-phase Ti using EBSD-based trace analysis. Acta Materialia, 61(20):7555–7567, 2013. doi: 10.1016/j.actamat.2013.08.042.