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A low carbon steel was processed by Cold Rolling (CR) and Asymmetrical Rolling (ASR) at room temperature until 200 µm thickness reduction using multiple rolling passes of 25 µm. ASR process induced a soft curvature with a 45.7 mm length and 128.8 mm radius, while the CR process did not show any curvature. Materials showed differences in the strain path as well as in the texture and microstructure evolution, not only concerning the mode of deformation but also across the sheet thickness. The hardness and tensile tests indicated a higher strength after processing by ASR than CR for the same thickness reduction. Changes in dislocation densities and grain size were more pronounced in the surface neighborhoods of the material processed by ASR than the as-received (AR) and CR conditions, while the grain size and the dislocation densities of the CR material were more homogeneous across the sheet thickness. Synchrotron measurements allowed to build dislocations and crystal size distribution functions. These functions demonstrated that for the surface zones for ASR condition, high dislocation densities correspond to the grains developing rolling texture components. In contrast, the highest dislocations densities for the center zone formed inside the smallest crystals with shear texture orientations. By ASR, a heterogeneous material with hard surfaces was generated using multiple small thickness reductions in a narrow and thick sheet. In contrast, with CR, a homogeneous hardness increase was obtained throughout the sheet's thickness, avoiding curvature in the material. It was found that high and heterogeneous distributions of geometrically necessary dislocations (GNDs) across the sheet thickness were responsible for the ASR material additional hardening.

Materials characterization 175, 111044 (1-12) (2021). doi:10.1016/j.matchar.2021.111044, Texture modification during sheet rolling appears differently in binary Mg-RE (rare-earth) or Mg-Ca alloy, compared to their ternary counterparts containing Zn. The differences in texture development and the active deformation mechanisms under tensile loading were investigated in the binary alloys. These analyses are based on in-situ synchrotron experiments and electron backscatter diffraction measurements to reveal direct experimental evidence of the texture development and the active deformation mechanisms. Higher activations of nonbasal < a > and pyramidal < c+a > dislocations were found in the Nd or Ca containing Mg alloys, compared to the Mg-Zn alloy. The texture development shows an obvious feature, which is a broadening of the basal pole intensity distribution perpendicular to the loading direction and a strengthening of the pole at the loading direction in all examined sheets. This texture development relates to the higher activation of prismatic < a > slip. The addition of Zn in the Mg-RE or Mg-Ca alloys further promotes the activation of nonbasal < a > and pyramidal < c+a > dislocations. This enhanced prismatic < a > slip in the Zn containing ternary alloys is confirmed by EBSD misorientation analysis., Published by Science Direct, New York, NY

In this study, high energy synchrotron radiation was used to perform an in-situ diffraction experiment in medium Mn Fe-6Mn-0.5C-1Al alloy to study the elemental partitioning and consequent austenite phase evolution at different stages, namely, during heating, holding and cooling. It has been observed that the austenite phase fraction significantly increases on annealing at the inter-critical annealing temperature and remains stable at room temperature. The austenite phase stability at room temperature is due to the rapid partitioning of manganese (Mn) and carbon (C) during annealing. The relative change in d-spacing (Δd/d) during heating-cooling confirms the partitioning of alloying elements during inter-critical annealing.

Materials science and engineering / A 726, 143 - 153 (2018). doi:10.1016/j.msea.2018.04.036, Synchrotron X-ray diffraction technique has been used to estimate defect structure in terms of dislocationdensity, crystallite size and micro-strain in commercially pure titanium subjected to tension and cyclic deformationin stress and strain control mode. Statistical analysis of micro-texture data collected from electronbackscatter diffraction approximately from the same region as that of synchrotron X-ray has been used to correlateorientation dependent micro-strain and dislocation density with deformation microstructure and microtexture.Two different orientations, namely, A with prismatic-pyramidal and B with basal orientation along theloading axis has been considered. Weak initial texture yet significant anisotropy in hardening/softening responseand failure mode for monotonic tension and cyclic loading paths has been observed. Higher strain hardeningresponse of orientation A during monotonic tensile deformation can be attributed to the evolution of lowermicro-strain on basal orientation grains i.e, 〈0002〉ǁND along with extensive multi-variant twinning that alsorestricts crack propagation and delays failure in stress control mode. On the other hand, in strain control mode,orientation B shows higher fatigue life due to the generation of lower micro-strain in the basal orientation grainsand single variant twinning that can undergo detwinning easily is responsible for delayed crack nucleation andsubsequent failure., Published by Elsevier, Amsterdam

Residual stress determination in engineering components from diffraction strain measurements needs reliable diffraction elastic constants (DECs). From this sense, in situ uniaxial tensile loading experiment was performed on alpha titanium alloy Ti–2.5Cu at the HEMS beamline at DESY by means of a monochromatic synchrotron X-ray diffraction. A comparison between measured (polycrystal) and calculated (single crystal) DECs using for example the Kroner model was presented and discussed. The results revealed that the measured DECs slightly differ from the calculated ones. Furthermore, changes in the lattice parameters a and c as well as c/a ratio during tensile loading were also investigated.

Laser shock peening can potentially enhance fatigue life of titanium components by inducing compressive residual stresses in surface layers much deeper than caused by traditional shot peening (SP). In the present study, the high cycle fatigue (HCF) performance of α Ti-alloy Ti–2.5Cu, (α + β) Ti-alloy TIMETAL 54M and the metastable β Ti-alloy TIMETAL LCB was investigated after laser shock peening without coating (LPwC). The fatigue results were interpreted by examining the changes of surface morphology, microhardness and residual stress generated in the surface layer. Furthermore, thermal stability of residual stresses in aged Ti–2.5Cu, as an example, was evaluated after annealing LPwC-treated material at various elevated temperatures and exposure times by applying a Zener–Wert–Avrami approach. The depth profiles of residual stresses were obtained by means of synchrotron X-ray diffraction or by incremental hole drilling method. Results revealed that the HCF performance of Ti–2.5Cu and TIMETAL LCB was markedly improved after LPwC, while it was deteriorated in TIMETAL 54M. Compared to LPwC, better 10 7 fatigue strength of Ti–2.5Cu was obtained after ball-burnishing (BB). Moreover, LPwC-induced residual stresses are thermally more stable than shot peening-induced ones.

Superelastic cyclic behavior of NiTi wires was studied by cyclically deforming several samples at impact strain rates on the order of 10 s −1 , using an instrumented tensile-impact device. The stress–strain cycles were performed up to different maximum strain ratios in order to study the cyclic impact fatigue for the incomplete, complete stress-induced martensitic transformation, and for the elastoplastic deformation of the martensitic phase. Impact results show that the stress-induced martensitic transformation stresses decrease with the number of cycles, although this decrease is lower than that obtained in cycling fatigue experiments performed at low strain rates. This suggests that the increment of the dislocation density, responsible for the stress reduction, depends on the strain rate applied during deformation. Moreover, the near-adiabatic condition fulfilled when deforming at high strain rates, promoting higher stress-induced martensitic transformation stresses during cycling at impact than the ones reached at low strain rates. In addition, the dissipated energy per cycle is also affected by the strain rate, being at impact 10–15% lower than the values obtained when the deformation occurs in isothermal conditions, that is at strain rates lower than 10 −4 s −1 .