FeCoSiBNbCu bulk metallic glass with large compressive deformability studied by time-resolved synchrotron Xray diffraction J. Appl. Phys. 115, 053520 (2014); 10.1063/1.4864671Fracture mechanism of some brittle metallic glasses
The relations between fatigue strength and other mechanical properties especially the tensile strength of metallic materials are reviewed. After analyzing the numerous fatigue data available, the qualitative or quantitative relations between fatigue strength and hardness, strength (tensile strength and yield strength) and toughness (static toughness and impact toughness) are established. Among these relations, the general relation between fatigue strength σw and tensile strength σb, σw = σb(C − P ⋅ σb), where C and P are parameters, (hereafter, the general fatigue formula) can well predict the fatigue strength with increasing the tensile strength in a wide range for many materials such as conventional metallic materials, newly developed materials and engineering components. On the basis of the experimental results of many materials, the fatigue damage mechanism, especially for high‐strength steels, is proposed. It is suggested that the general fatigue formula can provide a new clue to predict the fatigue strength and design the materials by adjusting material parameters P and C adequately.
Three typical interactions of persistent slip bands (PSBs) with different types of grain boundaries (GBs) were investigated and analyzed in fatigued copper crystals. The results show that PSBs cannot transfer through all types of large-angle GBs, regardless of their orientation with respect to the stress axis. Secondary slip was often observed near the GBs, leading to strain incompatibility. When the slip systems of the two adjacent crystals are coplanar, the transmission of a PSB across a GB strongly depends on the slip directions of the two adjacent crystals. It was found that only the low-angle GBs can be passed through by PSBs, and accordingly they are insensitive to intergranular fatigue cracking. For a special copper bicrystal with coplanar slip systems, the ladderlike dislocation arrangements within the adjacent PSBs become discontinuous and a dislocation-affected-zone appears near the GB due to the difference in the slip direction of the two adjacent crystals. Therefore, the necessary conditions for the transmission of a PSB across a GB are that the neighboring grains have a coplanar slip system and identical slip directions.
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