|About this Abstract
||2016 TMS Annual Meeting & Exhibition
||Mechanical Behavior at the Nanoscale III
||W-1: A Tale of Two Mechanisms: Strain-softening Versus Strain-hardening in Single Crystals under Small Stressed Volumes
||Yanfei Gao, Hongbin Bei
|On-Site Speaker (Planned)
Mechanical tests of defect-free single crystals exhibit strengths near the theoretical limit, and a pre-strain will lead to pre-existing defects that serve as the weakest links and reduce the measured strength. A pre-strain before testing a bulk sample will lead to strain hardening, in which the dislocation density increase makes it harder for plastic deformation to progress. The competition and synergy of the above strain-softening and strain-hardening mechanisms are systematically studied by nanoindentation pop-in tests at small scales (~micrometer) on Mo single crystals with different degrees of pre-strains and with a number of indenter radii. The primary effect of pre-strain is to shift the deformation mechanism from the homogeneous dislocation nucleation to a stochastic behavior, while the strain hardening behavior plays a secondary role. A master plot of pop-in strength versus indenter radius (normalized by pre-existing defect density) provides the critical guidance in interpreting a vast of small-scale mechanical tests.
||Planned: A print-only volume