SignificanceShear bands critically control the strength and ductility in a wide range of structural, geological, and biological materials. The nondestructive three-dimensional structural probing of individual shear bands has hitherto not been possible for investigation at the critical mesoscopic length scales. The X-ray microdiffraction study reported in this work reveals the highly localized stress gradients and microscopic damage mechanisms across the fatigue shear bands. The resulting local strain gradients lead to severe stress concentrations at the submicrometer scale, causing an anomalous deviation of the classical Coffin−Manson rule for the high-cycle fatigue failure of metals. This work opens an avenue for harnessing the synchrotron-based, 3D spatially resolved X-ray for studying the heterogeneous deformation and fracture in bulk materials.

No abstract

No abstract

No abstract

Uni-axial tensile test was conducted at room temperature on a weak texture AZ31B magnesium alloy at different strain rate, from 2.8×10-5s-1 to 1.1×10-1s-1. The mechanical behavior was investigated. It was found that as strain rate is increased, flat character of the stress-strain curves can be found and {10-12} tension twinning is responsible for this phenomenon. The sample exhibites a brittle fracture at 1.1×10-1s-1 strain rate while exhibites a ductile fracture character at 2.8×10-5s-1 strain rate.