Electron backscattering diffraction analysis of a reconstructed wootz damascus steel blade

The historical impact and subsequent fame of wootz weaponry in the ancient world has created interest in what has come to be seen as an advanced material even by modern standards. Ancient wootz artifacts are classed as high carbon (hypereutectoid) crucible steels and are characterised by high strength, hardness and wear resistance, but especially by their attractive surface pattern.

Effect of isothermal dissolution and re-precipitation of austenite on the mechanical properties of duplex structures

The hot deformation behaviour of a duplex ferritic/austenitic stainless steel was studied after different deformation conditions. The results showed a strange and interesting behaviour in the strength of the material during post-deformation studies. For most deformation conditions, the flow stress of the material was un-expectedly increased after annealing of deformed structures. This phenomenon implied that microstructural hardening occurred in the material during the interpass annealing rather than the expected softening. Also, an interesting change was observed where the morphology of the austenite phase changed from stringers or layers of austenite to a widmanstätten structure. The microstructural studies suggest that the austenite was dissolved and re-precipitated during the annealing process and the hardening was mostly associated with the change in the morphology of austenite.

Microstructure and properties of a C-Mn steel subjected to heavy plastic deformation

In the present paper an effect of severe plastic deformation (SPD) on the microstructural evolution and properties of a plain C-Mn steel was investigated. The SPD was accomplished by the MaxStrain system which deforms material along two perpendicular axes while the deformation along the third axis is fully constrained. The applied amounts of true strains were 5 and 20 in total. Deformation was conducted at room and 500°C temperatures. Some samples deformed at room temperature were subsequently annealed at 500°C. A microstructural analysis by SEM/EBSD was used for recognition the low- and high-angle grain boundaries. It was found that the collective effect of severe plastic deformation (true strain of 20) and further annealing promotes the formation of high-angle grain boundaries and uniform fine grained microstructure. The refinement of ferrite microstructure results in a significant increase in strength and hardness.

Texture and substructure development during post-dynamic softening in Ni-30%Fe austenite

The texture and substructure development during post-dynamic annealing of an austenitic Ni-30%Fe model alloy after complete dynamic recrystallization was investigated using electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). A novel mechanism of metadynamic softening is proposed based on the experimental investigation of the grain structure, crystallographic texture and dislocation substructure evolution. The initial softening stage involved rapid growth of the dynamically formed nuclei and migration of the mobile boundaries. The subboundaries within DRX grains progressively disintegrated through dislocation climb and dislocation annihilation, which ultimately led to the formation of dislocation-free grains, while the grain boundary migration gradually became slower. As a result, the DRX texture was largely preserved throughout the annealing process.

Wootz steel project by electron backscatter diffraction

The data is from an electron backscatter diffraction (EBSD) study of the microstructure of high carbon ‘Wootz’ steel. The objective of the study is to infer an unknown thermomechanical history from observation and analysis of the final microstructure in various ancient artefacts (swords and tools), and then compare the findings with heat treatments of the ancient artefacts and modern attempts at duplication of the structure. Electron backscatter data reveals the orientation relationships between various phases in the material, particularly cementite and ferrite.

Substructure development through dynamic recrystallisation in an austenitic Ni–30%Fe alloy

This data looks at the effect of grain boundary movement on the characteristics of substructure development within the DRX regime. Different thermo-mechanical processing routes were employed to produce a range of DRX grain sizes at a given deformation temperature. The development of dislocation substructure was investigated using electron back-scattered diffraction (EBSD) in conjunction with transmission electron microscopy (TEM).

The use of Fe-30% Ni and Fe-30% Ni-Nb alloys as model systems for studying the microstructural evolution during the hot deformation of austenite

The development of physically-based models of microstructural evolution during thermomechanical processing of metallic materials requires knowledge of the internal state variable data, such as microstructure, texture, and dislocation substructure characteristics, over a range of processing conditions. This is a particular problem for steels, where transformation of the austenite to a variety of transformation products eradicates the hot deformed microstructure. This article reports on a model Fe-30wt% Ni-based alloy, which retains a stable austenitic structure at room temperature, and has, therefore, been used to model the development of austenite microstructure during hot deformation of conventional low carbon-manganese steels. It also provides an excellent model alloy system for microalloy additions. Evolution of the microstructure and crystallographic texture was characterized in detail using optical microscopy, X-ray diffraction (XRD), SEM, EBSD, and TEM. The dislocation substructure has been quantified as a function of crystallographic texture component for a variety of deformation conditions for the Fe-30% Ni-based alloy. An extension to this study, as the use of a microalloyed Fe-30% Ni-Nb alloy in which the strain induced precipitation mechanism was studied directly. The work has shown that precipitation can occur at a much finer scale and higher number density than hitherto considered, but that pipe diffusion leads to rapid coarsening. The implications of this for model development are discussed.

Microstructural characterization of the austenite behaviour during metadynamic recrystallization

The work discusses the recent findings obtained from the microstructural characterization of an austenitic Ni-30%Fe model alloy during metadynamic recrystallization (MDRX) using both EBSD and TEM techniques. The characterization of the grain structure, texture and dislocation substructure evolution of the fully dynamically recrystallized (DRX) microstructure during post deformation annealing revealed a novel softening mechanism occurring under the current experimental conditions. It is proposed that the initial softening stage involves rapid growth of the dynamically formed nuclei and migration of the mobile boundaries in correspondence with the well-established MDRX mechanism. However, the sub-boundaries within DRX grains progressively disintegrate through dislocation climb and dislocation annihilation, which ultimately leads to the formation of dislocation-free grains. Consequently, the DRX texture largely remains preserved throughout the annealing process.

On the characteristics of substructure development through dynamic recrystallization

This body of data is the result of an investigation into the effect of grain boundary movement on the characteristics of substructure development in an austenitic Ni-30%Fe model alloy within the DRX regime. Different thermo-mechanical processing routes were employed to produce a range of DRX grain sizes at a given deformation temperature. The development of dislocation substructure was investigated using electron back-scattered diffraction (EBSD) in conjunction with transmission electron microscopy (TEM).

Role of microstructure in the low cycle fatigue of multi-phase steels

The low cycle fatigue (LCF) behaviour of several commercially-produced multiphase steels was studied; including dual-phase (DP) and transformation induced plasticity (TRIP). In addition, a novel TRIP980 hybrid microstructure was examined that consisted of coarse ferrite grains along with low temperature bainite regions interspersed with retained austenite. Fully reversed strain controlled fatigue tests were conducted on the different steels to determine the cyclic stress response and strain to failure. The effects of the cyclic deformation on the microstructures were analysed using electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). Results showed that the initial cyclic hardening behaviour and low cyclic softening ratio observed in the TRIP steels was not necessarily due to austenite to martensite transformation. Differences between the austenite transformation behaviour of the conventional and novel hybrid TRIP microstructures was related to the different surrounding phases and the size of the retained austenite.

Understanding of the bainite transformation in a nano-structured bainitic steel

A 0.79C-1.5Si-1.98Mn-0.98Cr-0.24Mo-1.06Al-1.58Co (wt%) steel was isothermally heat treated at 200°C for 10 days to form a nano-scale bainitic microstructure consisting of nanobainitic ferrite laths with high dislocation density and retained austenite films. The crystallographic analysis using TEM and EBSD revealed that the bainitic ferrite laths are close to the Nishiyama-Wassermann orientation relationship with the parent austenite. There was only one type of packet identified in a given transformed austenite grain. Each packet consisted of two different blocks having variants with the same habit plane, but different crystallographic orientations. The presence of fine C-rich clusters and Fe-C carbides with a wide range of compositions in bainitic ferrite was revealed by Three-dimensional Atom Probe Tomography (APT). The high carbon content of bainitic ferrite compared to the para-equilibrium level of carbon in ferrite, absence of segregation of carbon to the austenite/bainitic ferrite interface and absence of partitioning of substitutional elements between the retained austenite and bainitic ferrite were also found using APT.

Crystal orientation characterisation of electrodeposited nanocrystalline nickel alloy

The collection contains EBSD maps of annealed nanocrystalline Ni and Ni-Fe alloys. The maps show the variation of crystallographic texture across mesoscale colonies within these alloys.

Effective grain orientation on the substructure development of 304 stainless steel and NA-30% fe

This data is the result of an investigation into the effect of grain orientation on the substructure development of 304 stainless steel and a Ni-30wt.%Fe alloy. Both alloys have been used as model alloys to study the high temperature deformation of austenite. The development of the dislocation substructure as a function of strain, temperature and grain orientation was investigated using a combination of electron backscatterd diffraction (EBSD) and transmission electron microscopy (TEM).

Effect of grain size on deformation twinning in a magnesium alloy and commercial purity titanium

This data collection contains several optical microstructure images, EBSD maps and stress-strain curves. The research involves collecting data from samples with different grain sizes at several values of plastic strains to measure some important twinning parameters such as twin volume fraction and number of twins per grain. The aim of this study is to investigate the effect of grain size on deformation twinning behaviour in two hcp metals i.e. commercial purity titanium and AZ31 magnesium alloy.

Microstructural response of nanocrystalline Al to cyclic loading

The data is derived from an investigation into the microstructural changes of nanostructure Al (produced by cryo-rolling) in response to cyclic loading using electron microscopy and EBSD. The aim is to develop a better understanding of the deformation mechanisms in ultrafine grained/nanostructure metals under cyclic loading conditions.