E.J. Palmiere

EBSD study of the orientation dependence of substructure characteristics in a model Fe−30wt%Ni alloy subjected to hot deformation

The aim of the present investigation was to determine the orientation dependence of substructure characteristics in an austenitic Fe−30wt%Ni model alloy subjected to hot plane strain compression. Deformation was carried out at a temperature of 950 °C using a strain rate of 10 s−1 to equivalent strain levels of approximately 0.2, 0.4, 0.6 and 0.8. The specimens obtained were analysed using a fully automatic electron backscatter diffraction technique. The crystallographic texture was characterized for all the strain levels studied and the subgrain structure was quantified in detail at a strain of 0.4. The substructure characteristics displayed pronounced orientation dependence. The major texture components, namely the copper, S, brass, Goss and rotated Goss, generally contained one or two prominent families of parallel larger‐angle extended subboundaries, the traces of which on the longitudinal viewing plane appeared systematically aligned along the {111} slip plane traces, bounding long microbands subdivided into slightly elongated subgrains by short lower‐angle transverse subboundaries. Relatively rare cube‐orientated grains displayed pronounced subdivision into coarse deformation bands containing large, low‐misorientated subgrains. The misorientation vectors across subboundaries largely showed a tendency to cluster around the sample transverse direction. Apart from the rotated Goss texture component, the stored energy levels for the remaining components were principally consistent with the corresponding Taylor factor values.

Grain size measurement by EBSD in complex hot deformed metal alloy microstructures

The measurement of grain size by EBSD has been studied to enable representative quantification of the microstructure of hot deformed metal alloys with a wide grain size distributions. Variation in measured grain size as a function of EBSD step size and noise reduction techniques has been assessed. Increasing the EBSD step size from 5% to 20% of the approximate mean grain size results in a change in calculated arithmetic mean grain size of approximately 15% and standard noise reduction techniques can produce a further change in reported size of up to 20%. The distribution of measured grain size is found not to be log‐normal, with a long tail of very small sizes in agreement with a computer simulation of linear intercept and areal grain size measurements through randomly oriented grains. Comparison of EBSD with optical measurements of grain size on the same samples shows that, because of the ability of EBSD to distinguish twins and resolve much smaller grains a difference of up to 50% in measured grain size results.

Influence of strain reversal on dynamic transformation in microalloyed steels deformed above the Ae3 temperature

In the present work, the effect of strain path reversals on dynamic transformation (DT) above Ae3 temperature was studied using an API grade X-70 microalloyed steel deformed by torsion with single and multiple strain path reversals. The results revealed the important role played by strain path reversals on influencing the evolution of austenite grain boundaries through inhomogeneous deformation, therefore, affecting DT behaviours. In addition to flow stress–strain analysis and microstructure investigation, finite element method combined with 3D digital materials representation approach was used to gain insights into the effects of deformation with strain path reversals on the development of microstructural features in the prior-austenite grains.

The effect of thermomechanical controlled processing on recrystallisation and subsequent deformation-induced ferrite transformation textures in microalloyed steels

The evolution of texture components for two experimental 0.06xa0wt% C steels, one containing 0.03xa0wt% Nb (Nb steel) and the second containing both 0.03xa0wt% Nb and 0.02xa0wt% Ti (Nb–Ti steel), was investigated following a new thermomechanical controlled process route, comprising first deformation, rapid reheat to 1200xa0°C and final deformation to various strains. Typical deformation textures were observed after first deformation for both steels. Following subsequent reheating to 1200xa0°C for various times, the recrystallisation textures consisted primarily of the α-

Softening Kinetics of Plain Carbon Steels Containing Dilute Nb Additions

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Modelling the nucleation, growth and coarsening kinetics of γ ″ (D0 22 ) precipitates in the Ni-base Alloy 625

011//RD texture fibre with a weak γ-{111}//ND texture fibre, similar to deformation textures, indicative of the dominance of a strain-induced boundary migration mechanism. The texture components after finish deformation were different from the rough deformation textures, with a strong α-

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800 °C

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