Experimental evaluation of critical resolved shear stress for the first-order pyramidal c + a slip in commercially pure Ti by micropillar compression method
Kyosuke Kishida, Jim Geum Kim, Tadashige Nagae, Haruyuki Inui
Abstract
The plastic deformation behavior of commercially pure Ti single crystals has been investigated by uniaxial micropillar compression tests as a function of crystal orientation and specimen size at room temperature. {101¯1} (first-order) pyramidal c+a slip and prism a slip are activated in micropillar specimens with the [0001] and [21¯1¯0] orientations, respectively. {101¯1} pyramidal c+a slip has never been observed to operate as a major deformation mode in compression tests of ‘bulk’ single crystals at room temperature, in which {112¯2}<112¯3¯> twinning is usually observed. The CRSS values for {101¯1} pyramidal c+a slip and prism a slip increase with the decrease in the specimen size, following an inverse power-law relationship with a power-law exponent of about 0.06 and 0.59, respectively. The extrapolation of the inverse power-law relationship up to the ‘bulk’ specimen size estimated from the CRSS values of prism a slip gives the ‘bulk’ CRSS value for {101¯1} pyramidal c+a slip to be 580-635 MPa, which is by far higher than those for any other deformation modes operative at room temperature.