Effects of Stacking Fault Energy on the Deformation Mechanisms and Mechanical Properties of Face-Centered Cubic Metals

Stacking fault energy（SFE） can play a crucial role in plastic deformation and damage mechanisms of face-centered cubic（fcc） metals. This study mainly summarized the following results:（1）With the reduction of SFE, the slip mode of fcc metals gradually changes from a facile cross-slip wavy mode to a planar mode until deformation twinning occurs;（2） The concept of effective SFE is applied to investigate the variation of SFE with dislocation density in the fcc metals, with the increase in dislocation density, the effective SFE increases;（3） The reduction of SFE is not the only factor determining the formation of deformation twins in fcc metals. In terms of calculating the competition between simulated slipping and twinning using the first principles, the critical criterion for forming deformation twinning in fcc metals was established;（4） The fatigue dislocation configuration of high-, medium-, and low-SFE fcc metals were analyzed and the judgment conditions for forming regular persistent slip bands（PSBs） are proposed;（5） With the increase in Al content, the SFE of Cu-Al alloy decreases, resulting in a simultaneous increasing trend in the tensile strength and the uniform elongation due to the increasing planar slip degree;（6） The exponential strain-hardening model can accurately describe the tensile strain-hardening process of Cu-Al alloys. The quantitative relationship among yield strength, tensile strength, and uniform elongation of Cu-Al alloy with different alloy compositions and microstructure states was successfully predicted;（7） With the increase in Al content, the fatigue strength of Cu-Al alloy is improved. Increasing Al content at the same strain amplitude will enhance its low-cycle fatigue life. Based on the experimental results above, it is shown that the alloy composition affects the deformation and damage mechanisms, and the evolution process of microscopic defects（dislocations, twins） in fcc metals and alloys. Thus, it drastically affects the tensile and fatigue properties of the fcc metals and alloys. These results provide experimental evidence and a theoretical basis for improving the mechanical properties and service reliability of fcc metals and alloys via alloy designing.