Fig. 5
a The yield stress of nanotwinned Pd (nt-Pd) with a grain size of 10 nm as a function of the temperature. The calculated average flow stresses of nanotwinned Pd with two different twin thicknesses λ = 0.67 and 2.23 nm along with fitting curves based on Eq. 1, revealing the existence of a softening temperature Ts, defined by the intersection between the two fitting curves. Stress-controlled hardening is revealed below Ts, while source-controlled softening is observed above Ts. b The calculated flow stresses of nanotwinned Cu (nt-Cu) with two different twin thicknesses λ = 0.63 and 1.04 nm along with the theoretical fitting curves. Nanotwinned Cu has lower Ts as compared to nanotwinned Pd
