Papers by Keyword: Neutron Diffraction

Abstract: The stored energy during cold working has been estimated by two approaches. In the first approach, line broadening measurements were determined by neutron diffraction. The second approach is based on the model developed by Dillamore et al. [1]. Therefore, great attention has been paid to the influence of the deformation cell morphology, cell size and the eventual presence of orientation gradient inside the grains according to their orientation. Experimental results show this hierarchy E{111} <112> >E{111} <110>>E{001} <110>.

Abstract: This paper presents some ideas on incorporating output from advanced synchrotron and neutron scanning strain methods in improved assessment of the influence of weld process parameters on residual strains at welds and on their fatigue performance. It very briefly outlines two different cases involving synchrotron diffraction strain scanning of friction stir welds in a strain hardened aluminium alloy and neutron diffraction strain scanning of MIG welds in high strength steel.

Abstract: The corrosion resistance of sialons made from commercial powders (AlN, Al2O3 and Si3N4) and from powder precursor produced by carbothermal reduction and nitridation of raw aluminosilicate (pyrophyllite) in molten steel were investigated. The corroded zone in sialon made from raw pyrophyllite (P1) is more then two times deeper compared to the corroded zone of sialon made from commercial powders (C1). The corrosion zone of sample P1 is on the average 610 μm deep, while in sample C1 it is only 260 μm. The main corrosion products are γ-Al2O3 and iron silicides. The phase compositions were estimated by neutron Rietveld refinement.

Abstract: The layer growth of the A15 (Nb3Sn) superconducting phase produced by the internal tin method on model monofilament wires was studied by neutron diffraction and electron microscopy techniques. Different ratios of the inner part of the wire (Sn/Cu) and the effect of the addition of 1% of zirconium to niobium were studied. The high temperature heat treatment plays a key role on the A15 formation and on the cost of the final wires produced. Different temperatures in the range 650-725°C and different annealing times in the range 8-200 hrs have led to the preparation of 72 different samples. The neutron diffraction study has evidenced the different phases formed during the heating treatment and the electron microscopy study has evidenced a power law for the growth rate of the A15 phase. In both studies the addition of zirconium in niobium is very effective on the growth rate of the A15 phase.

Abstract: Although Friction Stir Welding (FSW) avoids many of the problems encountered when fusion welding high strength Al-alloys, it can still result in substantial residual stresses that have a detrimental impact on service life. An FE model has been developed to investigate the effectives of the mechanical tensioning technique for controlling residual stresses in FSWs. The model purely considered the heat input and the mechanical effects of the tool were ignored. Variables, such as tensioning level, heat input, and plate geometry, have been studied. Good general agreement was found between modelling results and residual stress measurements, justifying the assumption that the stress development is dominated by the thermal field. The results showed a progressive decrease in the residual stresses for increasing tensioning levels and, although affected by the heat input, a relatively low sensitivity to the welding variables. At tensioning levels greater than ~ 50% of the room temperature yield stress, tensile were replaced by compressive residual stresses within the weld.

Abstract: Dissimilar welded components joined with any kind of welding technologies gain an increasing interest due to significant improvements in engineering structures by using new materials (alloys) or new materials combinations. The present paper deals with laser welding of Al5083-H111 and Al6013-T6 and the characterization of the crystallographic texture. Fine grained Al5083 was joined with coarser grained Al6013.Whereas, Al6013 is strongly oriented dominated by a strong cube component and a much lower Goss component, the finer grained Al5083 shows a week deformation texture. The welding seam itself has a moderate cube texture with a minor <100> fiber texture in welding direction. A small texture variation about the texture strength and the volume fraction of the fiber component was observed along the weld. Results were obtained by neutron, hard X-ray and electron diffraction.

Abstract: Residual strain profiles in friction-stir processed (FSP) AZ31B magnesium-alloy plates were measured using neutron diffraction. Two different specimens were prepared to investigate the influences of the tool shoulder and the tool pin on the residual-strain profiles: (Case 1) a plate processed with both the stirring pin and tool shoulder, i.e., a regular FSP plate subjected to both the plastic deformation and frictional heating, and (Case 2) a plate processed only with the tool shoulder, i.e., subjected mainly to the frictional heating. The results show that the strain profiles of both cases are qualitatively quite similar. The longitudinal strain is mainly tensile with its maximum near the bead of the FSP plate. On the other hand, the transverse and normal strains are mildly compressive in both Cases 1 and 2.

Abstract: Textured Mg alloys exhibit tension – compression strength asymmetry due to mechanical twinning. The distinction arises as the material deforms primarily by slip in one direction and by twinning in the other. In-situ neutron diffraction during cyclic loading in tension and compression of extruded bar allows study of the effect of twinning on subsequent load reversals. The diffraction data reveal the texture evolution and internal stress development as a function of deformation. De-twinning resulted in complete texture reversal during initial cycles, but eventually “fatigued” resulting in some residual twin component.

Abstract: Magnetic field effect on a Heusler-type Ni2MnGa off-stoichiometric alloy having a martensitic transformation temperature around room temperature which is coincident with a Curie temperature has been investigated. The process of martensitic transformation of a single crystal was investigated by neutron diffraction under the magnetic field up to 8 [T]. It was found that the magnetic field, which is applied at a temperature near the transformation temperature, causes the martensitic transformation. The process of the transformation caused by the increase in magnetic field is quite similar to the process caused by the decrease in temperature.

Abstract: Dislocation density and crystallite size of steel wires with various carbon concentrations and drawing strains were determined by profile analyses for neutron diffraction profiles. The density is found to increase while the size decreases with increasing of carbon concentration and/or drawing strain. Both of the Bailey-Hirsch relation and Hall-Petch relation hold for the present results to suggest that these two are not independent., i.e., indicating an identical strengthening mechanism from a different point of view.