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Abstract: Correlations between the grain orientations and elastic properties of plasma-nitrided polycrystalline 316L austenitic stainless steel are investigated. The grain orientations (h k l) in a delimited area were obtained from electron backscatter diffraction and related to hardness (Hhkl ) and elastic modulus (Ehkl ) maps obtained from large nanoindentation matrices. The influence of nitrogen concentration on the local mechanical properties has been studied by repeating these indentation matrices in the same area after successive partial removals of the nitrided layer. This nanoindentation tomography allowed the orientation, the shape and the surroundings of individual grains to be taken into account. The results show that plasma nitriding leads to a complete reversal of the elastic behaviour anisotropy: while the non-nitrided 316L austenitic stainless steel shows the typical elastic anisotropy of face-centred-cubic-type metals with a maximum of Ehkl for the oriented grains, the maximum of Ehkl is observed for the oriented grains in the nitrided layer. A similar anisotropy reversal is observed for the hardness Hhkl . These observations are discussed on the basis of the microstructural changes induced by the nitrogen incorporation. [Copyright &y& Elsevier]

Statistics on nanoindentation experiments performed on a fourth-generation Ni-based single-crystal superalloy reveal a bimodal hardness distribution, with two mean hardness values only 2.5% away from each other. Using a hardness cartography technique combined with the statistical analysis proved that the hardness values are not randomly distributed but correspond exactly to the dendrites and the interdendritic regions. In this context, hardness cartography is shown to push back the resolution limit of the nanoindentation test. [ABSTRACT FROM AUTHOR]

The HIPing of Ti-Al-1.9TiC and Ti-Al-0.2Sn-1.8TiC reactant mixtures yields Ti3AlC2 and Ti3Al0.8Sn0.2C2 solid solutions, respectively. Rietveld refinement gives a = 3.0786 ± 0.0001 Å and c = 18.589 ± 0.001 Å lattice parameters for Ti3AlC2 and a = 3.0837 ± 0.0001 Å and c = 18.621 ± 0.002 Å for Ti3Al0.8Sn0.2C2. Furthermore, about 2-3 vol% of Ti x Al y intermetallics is detected in Ti3Al0.8Sn0.2C2 solid solution. The intrinsic hardness, measured by nanoindention tests, is 11.4 ± 0.7 GPa for Ti3AlC2 and 10.2 ± 0.6 GPa for Ti3Al0.8Sn0.2C2. Furthermore, hardness values, measured by microindentation tests, are compared with the ones measured by nanoindentation. It is shown that microindentation and nanoindentation performed with large loads lead to underestimated hardness values as several grains are involved in the deformation process. Finally, Young's modulus of Ti3AlC2 and Ti3Al0.8Sn0.2C2 is 260 ± 10 and 250 ± 10 GPa, respectively. [ABSTRACT FROM AUTHOR]

The plasticity of Ti3SnC2, a recently synthesized MAX phase, was investigated. Localized deformation was induced by nanoindentation in a polycrystalline sample, and the resulting surface topography was observed by atomic force microscopy (AFM). For several grains, buckling around the indent was observed, in agreement with the kink band deformation process often reported for MAX-phase materials. For other grains, slip lines have been revealed by AFM. The corresponding slip systems have been identified through the determination of the local crystalline orientation by electron backscatter diffraction. First- and second-order pyramidal slip systems are shown to be active for some grain orientations, as well as dislocation interactions and cross slip from one system to the other. [ABSTRACT FROM AUTHOR]

The changes in anisotropic hardness and indentation modulus induced by plasma nitriding at 400°C of a 316L polycrystalline austenitic stainless steel are analyzed. The dependence of hardness and elastic modulus modifications on the crystallographic orientation is investigated through instrumented indentation and electron backscattering diffraction. Both hardness and indentation modulus exhibit an inverted anisotropy compared to the untreated 316L, likely associated with the presence of the N atoms in interstitial sites. [ABSTRACT FROM AUTHOR]