Theoretical Characterization of the Temperature and Grain Size-Dependent Yield Strength of Fine-Grained Metals

Due to the characteristics of high strength and high toughness, fine-grained metals have a high application value in aerospace and defense industries. There are numerous studies to characterize the effects of temperature or grain size on yield strength separately. However, the model that can consider the combined effects of temperature and grain size is rarely reported. Herein, based on the temperature-dependent yield strength model and elastic modulus model established by the force-heat equivalence energy density principle, and considering the effect of grain boundary sliding, a temperature and grain size-dependent yield strength model of fine-grained metals which can take grain boundary sliding into account is developed. The model can predict the yield strength of fine-grained metals using an easily obtained yield strength at the coarse-grain size and an arbitrary reference temperature (usually room temperature). The predictions are in good agreement with all the available experimental data, which verifies the rationality of the proposed model. The quantitative influences of Young's modulus and fracture toughness on the yield strength at different temperatures and grain sizes are discussed, and useful suggestions for the preparation of fine-grained metals with higher yield strength from 77 K to 0.4 T-m are put forward.