13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- subsurface crack initiation owing to the compensatory tension. Hence, it is anticipated that VHCF life of AISI 310 can be enhanced due to UNSM. 2. Materials and Experimental Methods Cold rolled cylindrical rods of 12mm diameter of AISI 310 were used in this study. AISI 310 is a commonly used material in heat exchangers, pipes and machinery parts. The material exhibits excellent high temperature properties with good ductility and weldability. It resists oxidation at elevated temperature and corrosion in moist conditions and dry environments. Metallographic sample were prepared up to 0.05 micron finish and etched with Aqua Regia Reagent (15 mL HCL + 5 mL HNO3 + 100 mL H20) for 120 sec. The grain size of the material was determined by quantitative metallography and was found to be ~10 um as shown in Fig. 1. The grains were equiaxed and showed a random orientation. Carbide particles were obtained on the grain boundaries of the material. Elastic–plastic properties of the material were obtained by tensile testing according to ASTM standard E8 and are given in Table 1. Vickers microhardness tester was used at 200g load. The average Vickers hardness of the material was found as 370HV. Figure 1. SEM Micrograph of the material. Carbide precipitates are prominent on the grain boundaries Table 1. Mechanical property data for AISI 310 Material E (GPa) σy (MPa) Gauge length (mm) Hardness (HV) E / σy AISI 310 205 850 25 370 240 The chemical composition of the material is shown in Table 2. X-ray diffraction (XRD) was used to obtain the details of the diffracting planes and their preferred orientation. Diffraction planes (111), (200) and (220) were obtained for the material. The crystallographic orientations of diffracting planes were measured and it was found that the grains were randomly oriented without any preferred orientation. More details of the XRD and texture results can be found elsewhere [18]. Table 2. Composition of AISI 310 steel Material C% Cr % Ni % Si % Mn % Cu % Mo% P% Fe % AISI 310 0.04 23.3-23.4 18.9- 1.8 - 1.21 - 0.3 0.13-0.15 0.03 Bal
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