Focus on U.S. Investment Immigration, focus on U.S. Technology development: Recently, U.S. scholars studied the effect of sampling direction on the cyclic fatigue, deformation, and fracture behavior of high-strength alloy steel Pyrowear 53.
Compared with other high-strength alloy steels with similar chemical compositions and processing techniques, alloy steel Pyrowear 53 has significantly higher strength, plasticity, and toughness. In this study, the provided alloy steel bars were sampled from both transverse and longitudinal directions, and then finely processed and treated in accordance with the metallographic standards for tensile testing and stress-controlled cyclic fatigue testing.
The study reached the following main conclusions: First, the microstructure of the high-strength alloy steel mainly consists of ferrite islands distributed on martensite and uniformly dispersed, fine alloy carbides. The alloy composition determines that there is a considerable amount of martensite in the microstructure, mainly consisting of nearly acicular, extremely fine lath martensite. Second, the elastic modulus of the steel in the transverse direction is 10% lower than in the longitudinal direction, while the yield strength is the same. Third, the stress fatigue life of the longitudinal sampling specimens is lower than that of the transverse specimens. Fourth, there is local stress concentration at the interface between the ferrite phase and the martensite phase, which is highly detrimental to the fatigue resistance of the steel. Fifth, the fatigue fracture exhibits the characteristics of a local ductile-brittle failure mechanism. Sixth, the fatigue zone is mainly composed of short crack initiation sites, early micro-crack propagation zones, and short and obvious crack stable propagation zones.
