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Twenty different iron ore pellets, consisting primarily of Hematite (Fe2O3) phase, were subjected to 'simulated' reduction studies. A wide range of reduction time periods, Rt of 122 to 211 minutes, were obtained. Detailed microstructural characterizations were then conducted at different locations of ten selected specimens. The Rt did not relate with initial phase mix or chemistry but determined the final iron (Fe) to Wüstite (FeO1−x) ratio. In particular, numerical Rt values defined the relative presence of a bright Fe-rich rim. Further, relative density or porosity before the reduction scaled, as expected, with Rt. However, this was tenuous. The correlation appeared excellent in the post-reduction-densified specimens. This indicated the role of 'acquired porosity' and transformation strain. Several other microstructural parameters also scaled with Rt. These included grain size and crystallographic texture and estimated dislocation density. Lower Rt specimens had, in general, finer Fe2O3 and coarser Fe grains, but weaker crystallographic textures of Fe2O3 and FeO1−x. However, the most striking correlation appeared between Rt and post-reduction dislocation density. The acquired defect density, representing the transformation strain, appeared to be the controlling feature for the reduction of iron ore pellets. [ABSTRACT FROM AUTHOR]

This study showed significant improvements in resistance to oxidation of iron (Fe) with copper (Cu: 0–3.4 weight %) or phosphorous (P: 0–0.12 weight %) alloying. All these binary alloys had bcc ferrite structure and maintained (i) a homo-epitaxy with the oxide (magnetite–Fe3O4) phase below 843 K and (ii) a pseudo-epitaxy with pro-eutectoid magnetite > 843 K. The epitaxial growth, in particular, introduced dislocations, residual stress, and misfit strain in the 'thin' (a few hundred nanometer) oxide film. These were stronger for oxides on near ND||<111> Fe grains, but reduced noticeably with an increase in Cu or P content. The reduced epitaxial strain, residual stress and associated dislocations, appeared to correlate with the improved oxidation resistance—relating alloying and metal-oxide crystallography to oxidation resistance in dilute Fe–Cu and Fe–P binary alloys. [ABSTRACT FROM AUTHOR]

Super duplex stainless steel specimens were subjected to controlled (in a deformation simulator) thermal and thermal plus deformation treatments. The objective was to relate the corrosion performance with hot (1000-1300°C) deformed microstructures. The microstructural evolutions were quantified with extensive microtextural characterization and measurements of phase-specific micro-hardness. The corrosion behavior was investigated by anodic polarization and phase-specific selective dissolution methods. Though the thermal treatment imposed an increasing degradation in corrosion performance with holding temperature, the associated deformation at that temperature brought a non-monotonic behavior. The best corrosion performance (or the lowest passivation current density) was noted in the specimen deformed at ~1100°C. This superior corrosion behavior was attributed to the grain size refinement in the austenite phase. Finally, a combination of transmission Kikuchi diffraction (TKD) plus transmission electron microscopy (TEM) clearly related the grain size refinement to discontinuous dynamic recrystallization. The overall corrosion behavior was shown to be determined by a balance between decreasing austenite fraction and dynamic recrystallization-induced grain size refinement of the austenite phase. [ABSTRACT FROM AUTHOR]

Thirty-five 'apparently' recrystallized specimens were produced through a combination of cold rolling and recrystallization annealing. They had a range of average grain size (dav:18-467 μm), grain orientation spread (GOS: 0.31 to 1.24 deg) and volume fraction of ND||<111> ( V f N D | | < 111 > : 0.15-0.69). The GOS value, for individual grains or for an entire specimen, represented presence of 'remnant' cold work – existence of geometrically necessary dislocations and 'minor' orientation gradients. The resistance to aqueous corrosion was determined by this 'remnant' cold work, and not by average grain size or crystallographic texture. The role of mesoscopic distribution in plastic deformation, and the features of deformed microstructure, were then explored on the resistance to aqueous corrosion. Progressive plastic deformation, through laboratory cold rolling, brought reproducible non-monotonic corrosion responses. In particular, an increase in corrosion resistance (0 to 30 pct rolled) was followed by a drop (30-40 pct) and then an increase (> 40 pct rolling). These changes originated from the evolution in deformed microstructures: formation of near boundary orientation gradients and creation of low and high angle boundaries, respectively. A combination of microtexture and non-contact profilometry clearly established that deformation induced near boundary orientation gradients and grain-interior high angle grain boundaries provided resistance to aqueous corrosion, while low angle boundaries were detrimental. [ABSTRACT FROM AUTHOR]

This study involved hot working, mimicking the first strand of a compact strip production, of grain-oriented (GO) and non-grain-oriented (NGO) electrical steel. The as-cast microstructures, between the grades, were similar: large (~ 550 μm average diameter and 1 to 7 mm length) columnar grains with ND//〈001〉 fiber texture. However, the developments in hot-worked microstructures were remarkably different. Firstly, the GO had higher carbon (0.06 vs 0.003 weight pct)—which led to the presence of austenite phase at the hot working temperatures. The GO also showed dynamic recrystallization (DRx) and the presence of Goss (110)〈001〉 grains in the hot-worked state. These were absent in the NGO. Further, the majority (~ 95 pct) of the Goss grains, in the hot-worked GO, originated from dynamic recrystallization (DRx) in the ferrite phase, surrounding the harder prior austenite regions. This study thus identified DRx by particle-stimulated nucleation as the primary source of Goss orientation in the hot-worked GO. [ABSTRACT FROM AUTHOR]

A super duplex stainless steel was subjected to solution annealing at 1323 K. This led to grain coarsening, 'limited' (~ 7 pct by area) austenite-to-ferrite phase transformation and changes in phase-specific chemistry. No changes in the phase boundary nature or galvanic coupling between phases were, however, noted. The general corrosion behavior was determined by the electrochemical performance of the individual phases. The corrosion performance of the ferrite phase degraded monotonically with annealing time. This was related to a combined effect of grain coarsening and dilution in alloying (chromium and molybdenum content) elements. Corrosion of the austenite phase was, however, non-monotonic: as the effects of grain coarsening was counter-balanced, at least during the initial stages of annealing, by relative molybdenum enrichment. This study thus provided clear experimental data relating phase-specific corrosion performance with annealing induced changes in grain size and local chemistry in a super duplex stainless steel. [ABSTRACT FROM AUTHOR]

The serrated flow behavior of Al-Li, Al-Cu and Al-Cu-Li alloys was studied in solution-treated condition under a range of strain rates at ambient temperature. The serration behavior and the decrease in stress (i.e., the stress drop) in serrated flow curves are found to be dependent on both the magnitude of the strain rate and the nature and amounts of alloying elements present in these alloys. The underlying mechanisms behind the occurrence of serrations in these alloys are understood to be due to the interaction of solutes, both Cu and Li, with the dislocations. [ABSTRACT FROM AUTHOR]

Mechanical properties at ambient and cryogenic temperatures of Al-Cu-Li alloy are required for design and fabrication of liquid hydrogen and liquid oxygen tanks of satellite launch vehicles. In the present work, bead-on-sheet, friction stir welding was carried out with three different rotation speeds. The yield and strain hardening behaviors of the welds were evaluated in temperature range of 20 K to 298 K. Both yield stress and strain hardening ability in the specimen increased with decrease in testing temperature. The dependence of yield stress on temperature was modeled on the basis of thermally activated dislocation mobility, while that of strain hardening was modeled on the temperature dependence of dynamic recovery rate parameter. The recovery parameter followed an Arrhenius-type relationship with temperature. The model parameters determined from the experimental data were further used to simulate the stress–strain curves at different sub-zero temperatures for the friction stir welds. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Reduction of Iron Ore Pellets: A Microstructural Perspective" published in the journal Metallurgical & Materials Transactions. The correction states that A. Sarkar and V. Chavan are co-first authors of the article, which was not mentioned in the original online version. The correction has been made to the article. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. The article was authored by A. Sarkar, V. Chavan, N. N. Pai, A. Prakash, B. Hazra, P. Raut, D. Sunilkumar, C. Sivananda, S. Kundu, S. Nag, S. Basu, and I. Samajdar. [Extracted from the article]

The serrations in tensile stress–strain curves for Al-Cu-Li-based AA2198 alloy sheets were studied in various temper conditions. The alloy exhibited typical Portevin-Le-Chatelier effects with intense serrations in the stress–strain curves. This was observed in the solution-treated condition, while the intensity and frequency of serrations decreased upon aging. Detailed microscopic examination together with thermal stability studies showed the absence of δ′ (i.e., metastable Al3Li) precipitate in the alloy. As a result, the shearing of δ' precipitates by dislocations during plastic deformation did not occur in the present alloy. The quasistatic tensile testing as a function of test temperature, strain rate and temper condition and the acoustic emission study confirmed that the combined interaction of copper and lithium atoms with mobile dislocations is the underlying mechanism for the plastic instability in this alloy. The alloy displayed significant anisotropic behavior in terms of mechanical properties and serration characteristics, and these observations are related to the difference in the effective grain size of the samples in various orientations. [ABSTRACT FROM AUTHOR]

Fully recrystallized hexagonal Zirconium was subjected to controlled hot compression tests. Deformation above 723 K showed both flow saturation, characteristic of dynamic recovery, and also the presence of fine equiaxed grains, indicating dynamic recrystallization (DRx). Though data from relative work hardening were inconclusive, a combination of transmission Kikuchi diffraction plus transmission electron microscopy clearly confirmed the presence of DRx grains. A separation between the deformed and the DRx grains was not possible with microtexture or nano-indentation data. Local internal friction measurements (or tanδ values), however, clearly distinguished the DRx grains from both statically recrystallized (SRex) and the hot deformed grains. [ABSTRACT FROM AUTHOR]

Ductile-to-brittle transition in a low-alloy bainitic steel used as reactor pressure vessel material coincided with the change in brittle facet plane normal(s). Experimentally, it changed from ~ {100} facets at low temperatures to off-{100} planes at the higher temperatures. And such a change was also associated with brittle-to-ductile transition in the fracture mode. Molecular dynamics simulations, however, showed that the intrinsic cleavage plane remained {100} at all temperatures. Activation of atomistic mechanisms of crack kinking and dislocation pile-up, at higher temperatures, followed by the creation of atomistic ledges at the free surface resulted in the appearance of off-{100} facets. [ABSTRACT FROM AUTHOR]

Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys. [ABSTRACT FROM AUTHOR]

This article reports the occasional (< 10 pct of the actual production) delamination of pearlitic wires subjected to a drawing strain of ~ 2.5. The original wire rods which exhibited post-drawing delamination had noticeably lower axial alignment of the pearlite: 22 ± 5 pct vs 34 ± 4 pct in the nondelaminated wires. Although all wires had similar through-thickness texture and stress gradients, delaminated wires had stronger gradients in composition and higher hardness across the ferrite-cementite interface. Carbide dissolution and formation of supersaturated ferrite were clearly correlated with delamination, which could be effectively mitigated by controlled laboratory annealing at 673 K. Direct observations on samples subjected to simple shear revealed significant differences in shear localizations. These were controlled by pearlite morphology and interlamellar spacing. Prior-drawing microstructure of coarse misaligned pearlite thus emerged as a critical factor in the wire drawing-induced delamination of the pearlitic wires. [ABSTRACT FROM AUTHOR]

Eutectoid wire rods were subjected to controlled thermo-mechanical processing (TMP). Both increased cooling rate and applied stress during the austenite-to-pearlite decomposition produced significant changes in the microstructure: major increases in the pearlite’s axial alignment and minor decreases in the interlamellar spacing. The pearlite alignment was correlated with changes in the ferrite crystallographic texture and the state of residual stress. Microstructural engineering, improved axial alignment of pearlite, through controlled TMP gave a fourfold increase in torsional ductility. TMP of eutectoid steel thus appears to have interesting technological possibilities. [ABSTRACT FROM AUTHOR]

Near eutectoid fully pearlitic wire rod (5.5 mm diameter) was taken through six stages of wire drawing (drawing strains of 0 to 2.47). The as-drawn (AD) wires were further laboratory annealed (LA) to re-austenitize and reform the pearlite. AD and LA grades, for respective wire diameters, had similar pearlite microstructure: interlamellar spacing ( λ) and pearlite alignment with the wire axis. However, LA grade had lower hardness (for both phases) and slightly lower fiber texture and residual stresses in ferrite. Surprisingly, essentially identical tensile yield strengths in AD and LA wires, measured at equivalent spacing, were found. The work hardened AD had, as expected, higher torsional yield strengths and lower tensile and torsional ductilities than LA. In both wires, stronger pearlite alignment gave significantly increased torsional ductility. [ABSTRACT FROM AUTHOR]

Through-thickness microstructure development and residual stress evolution were explored in a part-pilgered Zircaloy-4 tube. Clear gradients in microstructure and residual stress were experimentally established at different locations. Such locations were considered along the axial length and also across the wall thickness. These were naturally subjected to different von Mises effective strains and were reflected on strain/microstructural gradients. The deformation gradients were also simulated with a three-dimensional elastoplastic finite element model. The model used both isotropic and anisotropic yielding. Though deformation gradients were similar with both yielding criteria, the anisotropic yielding provided a better match with experimental residual stress gradients. [ABSTRACT FROM AUTHOR]

Experimental forming limit curves (FLCs) were determined for two different grades of low-carbon steel: interstitial free (IF) and drawing quality (DQ). The grades had different interstitial content, clear differences in microstructural evolution, and differences in experimental FLCs. Microstructural evolution was generalized in terms of developments in crystallographic texture and in-grain misorientations. These were extrapolated further into dynamic values of normal anisotropy ( $$ \overline{r} $$ ) and strain hardening exponent ( n), respectively. FLCs were simulated by finite element (FE) analysis. Simulations were conducted using constant (or initial) and dynamic material properties (namely, $$ \overline{r} $$ and n). Simulations using the dynamic variation in the material properties showed better comparison to the experimental FLCs. [ABSTRACT FROM AUTHOR]

A commercial magnesium alloy was processed through multi-pass and multi-directional (unidirectional, reverse, and transverse tool movements) friction stir processing (FSP). Based on the FSP location, the dominant prior-deformation basal texture was shifted along the arc of a hypothetical ellipse. The patterns of deformation texture developments were captured by viscoplastic self-consistent modeling with appropriate velocity gradients. The simulated textures, however, had two clear deficiencies. The simulations involved shear strains of 0.8 to 1.0, significantly lower than those expected in the FSP. Even at such low shear, the simulated textures were significantly stronger. Microstructural observations also revealed the presence of ultra-fine grains with relatively weak crystallographic texture. Combinations of ultra-fine grain superplasticity followed by grain coarsening were proposed as the possible mechanism for the microstructural evolution during FSP. [ABSTRACT FROM AUTHOR]

Deformation twinning was directly observed in three commercial zirconium alloy samples during split channel die plane-strain compression. One pair of samples had similar starting texture but different grain size distributions, while another pair had similar grain size distribution but different starting textures. Extension twinning was found to be more sensitive to the starting texture than to the grain size distribution. Also, regions of intense deformation near grain boundaries were observed. A hierarchical binary tree-based polycrystal plasticity model, implementing the Chin-Hosford-Mendorf twinning criterion, captured the experimentally observed twinning grains' lattice orientation distribution, and the twin volume fraction evolution, provided the critical resolved shear stress for extension twinning, $$ \tau_{0} , $$ was assumed much larger than any of the values reported in the literature, based on the viscoplastic self-consistent model. A comparison of the models suggests that $$ \tau_{0} $$ obtained using the present model and the viscoplastic self-consistent models physically correspond to the critical stress required for twin nucleation, and twin growth, respectively. [ABSTRACT FROM AUTHOR]

This study involved edge regions of a friction stir processed (FSP) magnesium alloy (AZ31). Interleaved structures of ultra-fine, of few 100 nm, and coarser grains, several microns, were noted. Very short thermal anneals coarsened the former: generating typical micron-sized FSP grains. A model of microstructural development through grain boundary sliding of the ultra-fine grains was proposed. This model explains weaker texture in such grains and the fact that Mg-FSP shear texture did not change by successive passes. [ABSTRACT FROM AUTHOR]

The development of microstructure and crystallographic texture with effective strain at three through-thickness locations (near rolls, center, and near mandrel) in a partly pilgered Zircaloy-4 tube is described. Pilgering is found to eliminate through-thickness variation in grain size in the starting hot-extruded material and to generate location-dependent asymmetries in crystallographic texture. Deformation texture development during pilgering is modeled with polycrystal plasticity by idealizing the metal flow pattern as axisymmetric flow through a convergent channel. Good qualitative comparison of the predicted and experimental post-pilgering textures is obtained, provided location-dependent transverse shear component is superposed on the gross flow field, and localized deformation at grain boundaries is allowed. Frictional forces between tube and die are deduced from these observations. [ABSTRACT FROM AUTHOR]

Drawing Quality (DQ) and Interstitial Free (IF) steel strips, of identical specimen geometry, were uniaxially stretched using two servo hydraulic actuators moving in opposite directions at the same speed. Two strain levels were achieved, in a bending under tension testing setup, using a rigid cylindrical pin at the center of the respective strips. Different lubrication conditions brought into differences in microstructural developments and in macroscopic strain distributions. The latter was measured from digital image correlations, while measurements of in-grain misorientations and crystallographic textures were extrapolated into strain hardening exponent of Hollomon law (n) and normal anisotropy coefficient ( $$ \overline{r} $$). Finite element simulations were used to predict macroscopic strain distributions, assuming constant and varying (with strain) material properties of n and $$ \overline{r} $$. Predictions with variable material properties, as estimated from experimental microstructural data, were superior, having the least mean squared error (MSE). This study not only reiterates clear possibilities of incorporating microstructural inputs in a continuum model, but establishes efficacy of the same in relatively complex forming environment. [ABSTRACT FROM AUTHOR]

The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ε martensitic transformation, i.e., ε → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ε martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining 'pinned' ε martensite is unpinned by the decomposition of deformation-induced α′ martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ε → γ transformation finish temperature, A, increases with increase in pre-strain amount, though the reverse transformation start temperature, A, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α′ martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α′ martensite is seen to occur by the precipitation of FeNiSi-type intermetallic π-phase within these plates. [ABSTRACT FROM AUTHOR]

Non-grain oriented electrical steel, with minor in-grain orientation gradients, was subjected to interrupted tensile deformations and concurrent microtexture, magnetic property and residual stress measurements. After the upper yield point, clear signatures of mechanical stress relief were observed. Changes in orientation gradients led to annihilation of low-angle (1 to 3 deg) boundaries. Prior deformation compressive residual stresses became tensile and magnetic properties improved. Beyond an optimum true strain of 0.01, this boundary annihilation ceased, compressive stresses were generated, and magnetic properties degraded. [ABSTRACT FROM AUTHOR]

A hot-rolled Ni-Ti-Fe alloy was subjected to marforming: approximately 8 pct reduction (in thickness) in the martensite phase by laboratory rolling. Before the next marforming step, the sample was annealed to bring back calorimetric signatures of reversible austenite-martensite phase transformation. Significant differences in microstructure could be achieved by combinations of marforming and annealing. Such differences, on the other hand, originated from the marformed microstructure: two distinct regions of remarkably different substructures. The difference was mainly through the relative presence of defects: micro-twins and dislocations. The regions of lower defect densities got textured gradually, with marforming steps, to γ (ND//〈111〉) fiber. The regions with high defect densities, on the other hand, provided non- γ fine clustered grains after annealing. Though debates may continue on the exact nature and origin of micro-twins, the present study brought out their dominant role in determining almost all aspects of microstructural developments. [ABSTRACT FROM AUTHOR]

Different microstructures of Ni-Ti- and Ni-Ti-Fe-based shape memory alloys were subjected to thermal cycling: dipping in liquid nitrogen, for approximately 5 minutes, and then bringing it back to room temperature or austenite (cubic: B2) ↔ martensite (monoclinic: B19′) reversible solid-state phase transformation. Direct electron backscattered diffraction (EBSD) observations could bring out aspects of microstructural irreversibilities: namely, changes in grain size, misorientation buildup, and presence of retained martensite. The average changes in grain size (Δ d) differed by almost 2 to 4 times between different microstructures. The highest Δ d was typically observed in structures having maximum clustering of fine ( d < 5 μm) grains. The sample with highest Δ d was also subjected to multiple thermal cycling. Although Δ d scaled linearly with d after the first thermal cycle, the scatter increased during subsequent thermal cycles. Grain or orientations deviating from the linear behavior were clearly anisotropic crystallographically. With repeated thermal cycling, the patterns of changes in Δ d, austenite misorientation, and retained martensite content were similar. A phenomenological model or hypothesis, based on 40 deg $$ \left\langle {001} \right\rangle $$ orientation relationship between austenite and martensite phases, was proposed to address the observed patterns of microstructural irreversibility. [ABSTRACT FROM AUTHOR]

The application of the Avrami kinetics to study the evolution of dynamic recrystallization (DRX) in cadmium (Cd) is examined. The study involves compression testing of Cd over a range of temperatures and strain rates and flow curve analysis using a recently developed modeling technique. It is demonstrated that the Avrami relation is suitable to study the progress of DRX in Cd in a manner similar to that in various steels for which the concept was originally developed. [ABSTRACT FROM AUTHOR]

Deformation behavior of cobalt in the fcc phase was studied over a wide range of strain rates (0.001 to 1 s–1) and temperatures (600 °C to 950 °C). At the lower temperatures and higher strain rates, a single peak in flow stress followed by softening to steady state was observed, whereas at higher temperatures and lower strain rates, an oscillatory flow stress behavior finally converging to a steady state was observed. Both these represent typical flow stress responses during dynamic recrystallization (DRX). The critical condition for the initiation of DRX was determined by the inflection point in the work-hardening vs stress plot. This critical condition in terms of the work done was found to increase with temperature-compensated strain rate. Electron backscattered diffraction (EBSD) revealed that, on quenching after deformation, a certain fraction of the fcc phase was always retained, the extent of retention being higher for smaller grain sizes. Misorientation measurements across boundaries revealed a significant amount of twins in the retained fcc phase. The grain average misorientation (GAM), signifying the misorientation within grains, was found to be inversely related to the twin boundary fractions in the fcc phase. [ABSTRACT FROM AUTHOR]

Forming Limit Curves (FLCs) were determined experimentally through limiting dome height (LDH) tests in AA1050, AISI 316L and AISI 304L. FLCs were also simulated through FE (finite element) analysis. Simulations involved both constant and varying (with strain and strain path) material properties — namely, strain hardening exponent ( n) and normal anisotropy ( $$\bar r$$ ).Varying n values were estimated from limited experimental data (from tensile tests) and the implicit assumption that n scales with in-grain misorientation developments and formation of strain induced martensite. $$\bar r$$ , on the other hand, could be estimated from crystallographic texture only for AA1050. Simulations with varying $$\bar r$$ in AA1050 had shown a clear, though numerically marginal, improvement. On the other hand, varying n could remarkably improve the FLC predictability in 316L and 304L, especially in the biaxial region . [ABSTRACT FROM AUTHOR]

AA6022 samples were deformed at different temperatures and strain rates. Although deformation was immediately followed by quenching, as-deformed samples, especially samples subjected to higher deformation temperatures, contained a finite percentage of statically recrystallized grains. Crystallographic texture and microtexture measurements were employed to bring out developments in deformed and recrystallized microstructures and to outline the overall patterns of recrystallization. The latter was best represented through the so-called nucleation factor, an estimate of an orientation-sensitive nucleation. For a given orientation, nucleation factors were measured as the number of recrystallized grains divided by the number of deformed bands. With an increase in deformation temperatures, the dominance in nucleation appeared to have changed from cube $$ \left\{ {{\text{001}}} \right\}\left\langle {{\text{100}}} \right\rangle $$ to particle-stimulated nucleation (PSN) to cube again and, finally, to no preference. Relative stored-energy differences, with respect to working temperatures, explain the observed patterns in the orientation-sensitive nucleation. [ABSTRACT FROM AUTHOR]

The studies on hydrogen reduction of MoO3 indicated two main stages, namely, MoO3 to MoO2 and MoO2 to Mo. In both stages, temperature and time of reduction progressively increased on diluting hydrogen from 100 to 10 pct. Detailed kinetic analysis of the MoO2 to Mo stage was conducted by carrying out isothermal reduction between 625 °C and 900 °C by pure hydrogen. The kinetic equation was found to be $$ g{\left( \alpha \right)} = {\left[ { - \ln {\left( {1 - \alpha } \right)}} \right]}^{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 n}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$n$}}} = {\text{k}}t $$ , with n ranging from 1.49 to 2.13. The rate constant k obeyed the Arrhenius temperature dependence with the associated activation energy of 136 kJ mol−1. The X-ray diffraction (XRD) analysis of the product confirmed the phases predicted by thermal analysis. The scanning electron microscope (SEM) analysis of molybdenum powder revealed the presence of a greater number of pores and cracks in the individual particles produced at lower reduction temperatures and the tendency of acquiring spherical morphology with increasing reduction temperature. Based on the studies conducted, the optimum conditions for MoO3 to Mo reduction were predicted. [ABSTRACT FROM AUTHOR]

Intergranular corrosion and intergranular stress corrosion cracking are the two localized corrosion mechanisms that are of concern to the typical applications of austenitic stainless steels in industries. Until recently, the common understanding was that a higher frequency of random boundaries increases the susceptibility, caused by a sensitization heat treatment or by operating temperatures, of austenitic stainless steels to both intergranular corrosion and intergranular stress corrosion cracking. A recent study demonstrated that extreme randomization of grain boundaries leads to a considerable improvement of resistance to both sensitization and intergranular corrosion. This work is a continuation of Ref. 1 and relates the effects of grain boundary randomization to intergranular stress corrosion cracking: the results show a trend consistent with earlier observations on intergranular corrosion. It is shown that there is improvement in resistance to intergranular stress corrosion cracking with extreme randomization of grain boundaries. [ABSTRACT FROM AUTHOR]