Copper single crystal PSB morphology between 4.2 and 350 K

Abstract

For fatigue at temperatures from 4.2 to 350 K, crystals in saturation comprise PSB and matrix regions, however, details of PSB morphology are temperature-dependent. There are three main types of profile. Type I: at very low temperatrures, mildly bulged PSBs comprising smooth extrusions. Type II: from ≈15 to ≈250 K, triangular bulges reaching > 10 μm in height. Type III: above 300 K, non-bulged PSBs comprising both intrusions and extrusions. Transition regions with PSBs of mixed character are found between the distinct types. Room temperature is near the end of a transition region, PSB morphology therefore depends on fatigue conditions. PSB profile development is independent of fatigue environment; crack propagation is environment dependent. There is no correlation betwen PSB morphology and point defect mobility.