Widely used for structural materials in nuclear engineering, 316L austenitic stainless steel undergoes very high cycle fatigue (VHCF) throughout its service life. Since defects caused by service conditions are unavoidable in many engineering components during service life, the effects should be properly understood. In the present study, the effect of surface defects on the VHCF behavior were investigated on solution annealed (SA) and cold-worked (CW) 316L. Surface defects were artificially created using indentation. The VHCF test was conducted using an ultrasonic fatigue testing system. The results showed that the fatigue crack initiation was independent of the indent with the applied range of depth in this research. Furthermore, the critical depth of the indent was evaluated based on an empirical formula (Murakami’s model). In the case of SA 316L, the VHCF strength was not affected when the indent depth was less than 40 μm, which is consistent with the value obtained from the empirical formula. In the case of 20% CW 316L, the VHCF strength was not affected when the indent depth was less than 80 μm. The experimental results, i.e., the critical depth of the indent, were much larger than the results obtained from the empirical formula, and might have been caused by the plastic deformation, residual stress, and probable deformation-induced martensite transition around the indent.

Titanium alloys are usually subjected to hot deformation to optimize its microstructure and mechanical property. In the hot forming process, such as extrusion, texture is of great importance to both manufacturing and performance. In this study, an alpha-beta titanium was used to study the texture evolution during hot extrusion. Large area electronic backscattering scan was used to examine grain orientation distribution. Experimentally measured alpha and beta textures were compared with a rate-dependent crystal plasticity based simulation. The model is capable of predicting the deformation textures of both alpha and beta phases at extrusion temperature. The model also takes into account the transformation of metastable beta phase to alpha phase in the cooling process, considering variant selection. The transformation texture components mostly have [0001] along extrusion direction, forming the primary component of alpha extruded texture. The model works well in predicting hot deformation texture of titanium alloy.