This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (À60°C) in order to obtain a different volume fraction of strain-induced martensite (up to~70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (a¢ fi c). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted-strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.
et al.. Multireflection grazing incidence diffraction used for stress measurementsin surface layers. Thin Solid Films, Elsevier, 2013, 530, pp.a b s t r a c t
Keywords:Residual stress X-ray diffraction Synchrotron radiation Grazing incidence method The geometry based on the multireflection grazing incidence X-ray diffraction can be applied to measure residual stresses. Using this method, it is possible to perform a non-destructive analysis of the heterogeneous stresses for different and well defined volumes below the surface of the sample (range of several μm). As the result, the average values of stresses weighted by absorption of X-ray radiation are measured. In this work the stress profiles as a function of penetration depth were determined for mechanically polished Al sample. Measurements and verification of the method were performed using classical X-ray diffractometer and synchrotron radiation with different wavelengths.
The multireflection grazing‐incidence X‐ray diffraction (MGIXD) method is commonly used to determine a stress gradient in thin surface layers (about 1–20 µm for metals). In this article, the development of MGIXD to enable the determination not only of stresses but also of the c/a ratio and the a0 strain‐free lattice parameter in hexagonal polycrystalline materials is presented and tested. The new procedure was applied for the results of measurements performed using a laboratory X‐ray diffractometer and synchrotron radiation. The evolution of stresses and lattice parameters with depth was determined for Ti and Ti‐alloy samples subjected to different mechanical surface treatments. A very good agreement of the results obtained using three different wavelengths of synchrotron radiation as well as classical X‐rays (Cu Kα radiation) was found.
is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tMulti-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al-Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al-Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin 2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined.
Multireflection grazing-incidence X-ray diffraction was used to investigate the structure and residual stress gradients in the near-surface region of mechanically treated titanium samples. The development of this method by using a white synchrotron beam during an energy dispersive diffraction experiment is proposed.
International audienceMultireflection grazing-incidence X-ray diffraction (MGIXD) was used to determine the stress- and strain-free lattice parameter in the surface layer of mechanically treated (polished and ground) tungsten and austenitic steel. It was shown that reliable diffraction stress analysis is possible only when an appropriate grain interaction model is applied to an anisotropic sample. Therefore, verification of the X-ray stress factors (XSFs) was accomplished by measuring relative lattice strains during an in situ tensile test. The results obtained using the MGIXD and standard methods ( and geometries) show that the Reuss and free-surface grain interaction models agree with the experimental data. Moreover, a new interpretation of the MGIXD results was proposed and applied for the first time to measure the probability of stacking faults as a function of penetration depth for a polished and ground austenitic sample. The XSF models verified in the tensile test were used in the analysis of residual stress components
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