Temperature-affected nano-deformation behavior of nanometals in ultrahigh-strain-rate formation processes.

As metal forming processes move toward high speed, high throughput, high precision and small scale with temperature dependence, clarifying the fundamental nano-deformation behavior of metals is critical for the optimization of manufacturing processes, and the control of nano-optical, electrical, mechanical or surface properties. Unfortunately, limited by the time scale and sample size, the effect of temperature on the deformation behavior of nano-metals during the ultrahigh-strain-rate forming process remains largely unexplored. This study demonstrates the nonlinear effect of temperature on the formability of nano-metals for the first time. Temperatures below 673 K facilitated the formability of nano-metals benefiting from the temperature-promoted dislocation proliferation process, whereas temperatures above 673 K weakened the plasticity of the nano-metal due to the activation of phase transformation. Frequent phase transition activation and accelerated dislocation annihilation at high temperatures reduced interstitial transport channels and delayed atomic transfer. Based on the temperature response of nano-metals in deformation mechanisms, defect evolution behavior and formability, the constitutive model and nano-deformation mechanism map of nano-metals in ultrahigh-strain-rate forming processes are proposed. The objective of this work is to provide basic support for the reasonable matching of nano-forming technology and processing temperature, and the determination of the optimal process window through fundamental nano-deformation behavior exploration.