Evolution of Deformation and Recrystallization Textures in High-Purity Ni and the Ni-5 at. pct W Alloy

An attempt has been made to study the evolution of texture in high-purity Ni and Ni-5 at. pct W alloy prepared by the powder metallurgy route followed by heavy cold rolling (~95 pct deformation) and recrystallization. The deformation textures of the two materials are of typical pure metal or Cu-type texture. Cube-oriented ({ 00 1 } á 100 ñ \left\{ {00 1} \right\}\left\langle { 100} \right\rangle ) regions are present in the deformed state as long thin bands, elongated in the rolling direction (RD). These bands are characterized by a high orientation gradient inside, which is a result of the rotation of the cube-oriented cells around the RD toward the RD-rotated cube ({ 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle ). Low-temperature annealing produces a weak cube texture along with the { 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle component, with the latter being much stronger in high-purity Ni than in the Ni-W alloy. At higher temperatures, the cube texture is strengthened considerably in the Ni-W alloy; however, the cube volume fraction in high-purity Ni is significantly lower because of the retention of the { 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle component. The difference in the relative strengths of the cube, and the { 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle components in the two materials is evident from the beginning of recrystallization in which more { 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle -oriented grains than near cube grains form in high-purity Ni. The preferential nucleation of the near cube and the { 0 1 3 } á 100 ñ \left\{ {0 1 3} \right\}\left\langle { 100} \right\rangle grains in these materials seems to be a result of the high orientation gradients associated with the cube bands that offer a favorable environment for early nucleation.     

Formation of textures in a C–Si–V dual-phase steel

A vanadium microalloyed steel (0.1 C, 1.50 Si, 0.1 V) was subjected to initial heat treatments and intercritical annealing at 750 and 810°C to produce dual-phase structures of different distribution. Intercritically annealed materials were cold-rolled to a reduction of 60% in thickness and small samples taken from them were recrystallisation annealed at two temperatures of 650 and 800°C for various lengths of time. The (110) pole-figures for the cold-rolled materials with different dual-phase distribution showed a strong {111}< 112 > and a rather weak {111}< 110 > texture components. The O.D.F. (orientation distribution function) plots also showed the major texture components, {111}< 112 > and {111}< 110 > along with the minor components, like, {337}< 110 >, {337}< 776 >, {112}< 111 > and {112}< 110 >. No complete {111} fibre has been observed in the present investigation. Further the orientations{11, 11,4}< uvw > and {337}< uvw > have been found to be present as weak and incomplete fibre. The (110) pole-figures of the recrystallised materials have shown similar features (with reduced pole densities) as compared to the cold-deformed materials. Similarly, no {111} fibre has been observed in the recrystallised materials. The behaviour of the other two components, namely {11, 11,4}< uvw >, and {337}< uvw > have been found to be similar to that in the cold deformed material.     

Precipitation in Nb-Stabilized Ferritic Stainless Steel Investigated with <Emphasis Type="Italic">in-situ</Emphasis> and <Emphasis Type="Italic">ex-situ</Emphasis> Transmission Electron Microscopy

A Nb-stabilized Fe-15Cr-0.45Nb-0.010C-0.015N ferritic stainless steel is studied with transmission electron microscopy (TEM) to investigate the morphology and kinetics of precipitation. Nb_x(C,N)_y\hbox{Nb}_{x}\hbox{(C,N)}_y and MnS precipitates are present in the steel in the initial condition. Ex-situ TEM analysis is performed on samples heat treated at 973 K, 1073 K, 1173 K, and 1273 K (700 °C, 800 °C, 900 °C, and 1000 °C). Within this temperature range, both Fe₂Nb\hbox{Fe}_2\hbox{Nb} and Fe₃Nb₃X_x\hbox{Fe}_{3}\hbox{Nb}_{3}\hbox{X}_{x} (with X = C or N) precipitates form. Fe₂\hbox{Fe}_2Nb is observed at 1073 K (800 °C).   Fe₃Nb₃X_x\;\hbox{Fe}_{3}\hbox{Nb}_{3}\hbox{X}_{x} precipitates form at the grain boundaries between 973 K and 1273 K (700 °C and 1000 °C). Up to at least 1173 K (900 °C) their fraction increases with time and temperature, but at 1273 K (1000 °C) they lose stability with respect to Nb_x(C,N)_y.\hbox{Nb}_{x}\hbox{(C,N)}_{y}. With in-situ TEM, no phase transition is observed between room temperature and 1243 K (970 °C). At 1243 K (970 °C) the precipitation of Fe₃Nb₃X_x\hbox{Fe}_{3}\hbox{Nb}_{3}\hbox{X}_{x} is observed in the neighborhood of a dissolving Nb₂\hbox{Nb}_2(C,N) precipitate. For sections of grain boundaries where no Nb_x(C,N)_y\hbox{Nb}_x\hbox{(C,N)}_y precipitates are present, Fe₃Nb₃X_x\hbox{Fe}_3\hbox{Nb}_3\hbox{X}_{x} does not form. It is concluded that the precipitation of Fe₃Nb₃X_x\hbox{Fe}_{3}\hbox{Nb}_{3}\hbox{X}_x is directly related to the dissolution of Nb₂\hbox{Nb}_2(C,N) through the redistribution of C or N.     

A theoretical examination of the plastic deformation of ionic crystals: III. Mixed {110}, {100}, {111} 〈110〉 slip and approximate 〈110〉 pencil glide

Calculations have been made of the Taylor factorM and of the lattice rotation for crystals undergoing axisymmetric flow and deforming by approximate 〈110〉 pencil glide. Two types of approximate 〈110〉 pencil glide were considered: 1) mixed slip on {110}, {l00}, and {111} 〈110〉 systems and 2) slip on a set of equally spaced slip planes containing each (110) slip direction. The results indicate that the pencil glide mode tends to reduce the plastic anisotropy in axisymmetric flow in contrast to the 〈111〉 slip modes in bcc metals. The lattice rotation is such that the fiber axis tends toward 〈111〉 in tension (〈lOO〉minor tendency) and toward 〈110〉 in compression. This result is similar to that of {lll}〈110〉 slip in fcc metals. We have also calculated the Taylor factors for mixed {110}〈110〉 + {lll}〈110〉 slip and for mixed {l00}(110) + {lll}〈110〉 slip. These mixed modes, together with the {lll}〈110〉 and the mixed {l00}〈110〉 + {110}〈110〉 slip modes previously analyzed, constitute all possible slip modes among {lll}〈110〉, {l00}(110), and {ll0}〈110〉 systems accommodating an arbitrary shape change. The conditions governing the activation of the various mixed modes have also been determined.     

Mechanisms of Ductility in CoTi and CoZr B2 Intermetallics

The present research is conducted in order to elucidate the operative deformation mechanisms allowing ductility in the B2 (CsCl) intermetallics CoTi and CoZr. A twofold approach combines in-situ neutron diffraction during uniaxial compression with elastoplastic self-consistent (EPSC) polycrystal modeling. Tensile and compression tests of CoZr and CoTi confirm that both intermetallics are ductile at room temperature. Low compressive yield points of −62 and −50 MPa are identified for CoTi and CoZr, respectively. Analysis of stress-strain curves, in-situ neutron diffraction internal strain measurements, and EPSC modeling confirm that the initial plasticity is accommodated via the established á 100 ñ { 0 1 1 } \left\langle { 100} \right\rangle \left\{ {0 1 1} \right\} slip mode. However, a sudden decrease in the hardening rate observed in the macroscopic stress-strain curve and apparent in the internal stress developments signals the activation of a secondary mechanism, which helps to explain the anomalous ductility. The EPSC simulations involving either á 1 10 ñ { [`1] 10 } \left\langle { 1 10} \right\rangle \left\{ {\overline{1} 10} \right\} or á 1 1 1 ñ { 1[`1] 0 } \left\langle { 1 1 1} \right\rangle \left\{ {1\overline{1} 0} \right\} slip mechanisms coupled with á 1 0 0 ñ \left\langle { 1 0 0} \right\rangle slip can reproduce the observed transitions at −350 and −250 MPa for CoTi and CoZr, respectively. Implications related to previous observations of a yield strength anomaly and the possible influence of kink banding are discussed.     

Influence of initial ingot breakdown on the microstructural and textural development of high-purity tantalum

The influence of initial ingot breakdown on the rolling and recrystallization textures of high-purity tantalum plate was investigated using optical microscopy and X-ray diffraction. The four ingot breakdown processes investigated include two commercial processes and two processes new to tantalum. Correlations among the four ingot breakdown processes, the recrystallized grain size, and the final texture were established. Of the four breakdown processes investigated, the plate from the completely upset-forged ingot had the strongest {111}<110> and {111}<112> texture components, while the plate from the side-forged ingot recrystallized with a mixed texture. Increased upset forging along the ingot centerline strenghened the {111}<uvw> orientations and weakened the {100}<uvw> orientations in the annealed plates. Recrystallization studies were conducted on the rolled plates to develop an optimum texture with both {111}<110> and {111}<112> texture components in the final recrystallized plate.     

Deformation behavior of long-range ordered AgMg

The deformation behavior of long-range ordered AgMg single crystals was investigated in tension and compression for several orientations and temperatures. The study revealed that AgMg exhibits a complex and asymmetric deformation behavior corresponding to the operation of two different primary slip vectors, <111> and <001>, whose activation depends on the crystallographic orientation and sense of the applied uniaxial stress and on temperature. Crystals of various orientations deformed between 20° and 298°K exhibited six different operative slip systems, {112} <111>, {123} <111>, {110} <111>, {120} <001>, {100} <001>, and {110} <001>. It is shown that the high strain-hardening rate exhibited by polycrystalline AgMg does not arise from the Vidoz-Brown⁵ mechanism of formation of antiphase boundary (APB) tubes on jogged superdislocations, but is associated with the operation of the {hko} <001> slip systems.     

Twinning-induced sluggish evolution of texture during recrystallization in AISI 316L stainless steel after cold rolling

This paper deals with the evolution of texture in AISI 316L austenitic stainless steel during annealing after 95 pct cold rolling. After 95 pct cold rolling, the texture is mainly of the brass type {110}〈112〉, along with a scatter toward the S orientation {123}〈634〉 and Goss orientation {011}〈100〉. Weak evidence of Cu component is observed at this high deformation level. During annealing, recovery is observed before any detectable recrystallization. Recrystallization proceeds through nucleation of subgrain by twinning within the deformed matrix and, later, preferential growth of those to consume the deformed matrix. After recrystallization, the overall texture intensity was weak; however, there are some discernible texture components. There was no existence of the brass component at this stage. Major components are centered on Goss orientation and Cu component {112}〈111〉 as well as the BR component {236}〈385〉. Also, a few orientations come up after recrystallization (i.e., {142}〈2−11〉 and {012}〈221〉). With increase in annealing temperature, the textural evolution shows emergence of weak texture with another new component, {197}〈211〉. The evolution of texture was correlated with the deformation texture through twin chain reaction.     

Effect of texture and microstructure on resistance to cracking of high-strength hot-rolled Nb-Ti microalloyed steels

Significant texture gradient in the through-thickness direction was observed in high-strength hot-rolled 560 and 770 MPa Nb-Ti microalloyed steels, characterized by polygonal ferrite and ferrite bainite microstructures, respectively. {113}〈110〉 was the most intense deformation texture in the two high-strength grades of Nb-Ti steels and was dominant in the midthickness region compared to 10 and 25 pct depth below the surface. The recrystallization texture of austenite, {100}〈001〉, transformed into {100}〈011〉 component in the ferrite and indicated an increase in the intensity with increase in depth for the Nb-Ti microalloyed steels. The {100}〈011〉 texture has a detrimental effect on the edge formabiity of steels. However, the midthickness plane contained considerable intensity of desired texture, {332}〈113〉, which is expected to offset the undesirable {100}〈011〉 texture resulting in superior edge formability and impact toughness of Nb-Ti steels, consistent with experimental observations.     

New annealing textures in commercial Al−Mg alloys

A number of new textures have been observed in rolled and annealed magnesium-bearing aluminum alloys. The textures contain various proportions of {100} <013> or {100} <015> oriented material, together with components near {110} <332>, or {2, 13, 15} <13, 10, 11> or {4, 11, 14} <11, 6, 8>. They result from recrystallization, and involve the migration of high-angle boundaries similar to those associated with the formation of the more commonly observed cube texture. The origin of these textures is explained in terms of current theories of recrystallization texture formation, and their occurrence is attributed to the absence of {358} <835> and {110} <112> components in the rolling texture. This in turn is attributed to preferred orientations in the as-cast starting material prior to rolling.     

Calculation of the product phase grain edge length and quadruple points per unit volume during solid state transformations

General expressions are derived for the calculation of the total product phase grain edge length per unit volume L _V ^βββ and the total number of product phase quadruple points per unit volume QV (i.e., ββββ quadruple points) at any given time during solid state transformations occurring by nucleation and growth process. It is shown that, {

Self-diffusion of copper in Cu−Al solid solutions

Self-diffusion coefficients of copper in Cu?Al solid solutions in the concentration interval 0 to 19 at. pct Al and in the temperature range 800° to 1040°C have been determined by the residual activity method using the isotope Cu⁶⁴. The values of the self-diffusion coefficients in the concentration interval 0 to 14.5 at. pct Al satisfy the Arrhenius relation and their temperature dependence can be expressed by the following equations $$\eqalign{ & D_{Cu}^{Cu} = \left( {0.43_{ - 0.11}^{ + 0.15} } \right) exp \left( { - {{48,500 \pm 700} \over {RT}}} \right) cm^2 /\sec \cr & D_{Cu - 2.80 at. pct Al}^{Cu} = \left( {0.46_{ - 0.16}^{ + 0.23} } \right) exp \left( { - {{48,000 \pm 900} \over {RT}}} \right) cm^2 /\sec \cr & D_{Cu - 5.50 at. pct Al}^{Cu} = \left( {0.30_{ - 0.07}^{ + 0.09} } \right) exp \left( { - {{47,000 \pm 600} \over {RT}}} \right) cm^2 /\sec \cr & D_{Cu - 8.83 at. pct Al}^{Cu} = \left( {0.46_{ - 0.09}^{ + 0.11} } \right) exp \left( { - {{47,100 \pm 500} \over {RT}}} \right) cm^2 /\sec \cr & D_{Cu - 11.7 at. pct Al}^{Cu} = \left( {0.61_{ - 0.13}^{ + 0.17} } \right) exp \left( { - {{47,200 \pm 600} \over {RT}}} \right) cm^2 /\sec \cr & D_{Cu - 14.5 at. pct Al}^{Cu} = \left( {4.2_{ - 1.5}^{ + 2.2} } \right) exp \left( { - {{51,110 \pm 1000} \over {RT}}} \right) cm^2 /\sec \cr} $$ An analysis of the results leads to the conclusion that, in the concentration interval 0 to 11.7 at. pct Al, the frequency factor and activation enthalpy concentration dependences can be described by the following equations whereD _0Cu ^Cu and ΔH _Cu ^Cu are diffusion characteristics for self-diffusion in pure copper,X _Al is the atomic percent of aluminum, andK andB are experimental constants.     

Kinetics of hydrochloric acid leaching of smithsonite

The dissolution kinetics of smithsonite ore in hydrochloric acid solution has been investigated. As such, the effects of particle size (−180 + 150, −250 + 180, −320 + 250, −450 + 320 μm), reaction temperature (25, 30, 35, 40, and 45°C), solid to liquid ratio (25, 50, 100, and 150 g/L) and hydrochloric acid concentration (0.25, 0.5, 1, and 1.5 M) on the dissolution rate of zinc were determined. The experimental data conformed well to the shrinking core model, and the dissolution rate was found to be controlled by surface chemical reaction. From the leaching kinetics analysis it can be demonstrated that hydrochloric acid can easily and readily dissolve zinc present in the smithsonite ore, without any filtration problems. The activation energy of the process was calculated as 59.58 kJ/mol. The order of the reaction with respect to HCl concentration, solid to liquid ratio, and particle size were found to be 0.70, −0.76 and −0.95, respectively. The optimum leaching conditions determined for the smithsonite concentrate in this work were found to be 1.5 M HCl, 45°C, −180 + 150 μm, and 25 g/L solid to liquid (S/L) ratio at 500 rpm, which correspond to more than 95% zinc extraction. The rate of the reaction based on shrinking core model can be expressed by a semi-empirical equation as:

Formation of Nuclei With {111}<110> and {111}<112> Orientations of IF Steel at Early Stage of Recrystallization Using EBSD Analysis

The excellent deep drawability of interstitial free steel (IF steel) is closely related to its texture formed during recrystallization. The nucleation process of cold rolled IF steel at the early stage of recrystallization was investigated by electron back scattered diffraction (EBSD). The characteristics of the microstructure after deformation and the orientation of nucleation were observed. The results show that the deformed microstructure with 80% reduction could be subdivided into two groups. These two types of microstructure were characterized by their orientation and internal local misorientations. The nuclei with γ-orientation preferred to form in deformed bands with γ-orientation and at the boundaries between deformed grains with different orientations. The recrystallized grains with {111}<110> orientation appeared firstly in deformed matrix with {111}<112> orientation and consumed the matrix with {111}<112> to grow up, while the recrystallized grains with {111}<112> orientation were observed secondly in deformed matrix with {111}<110> orientation and consumed matrix with {111}<110> to grow up.     

Thermodynamics of iron-aluminum alloys at 1573 K

The activities of iron (Fe) and aluminum (Al) were measured in Fe-Al alloys at 1573 K using the ion-current-ratio technique in a high-temperature Knudsen cell mass spectrometer. The Fe-Al solutions exhibited negative deviations from ideality over the entire composition range. The activity coefficientsγ _Fe, andγ _A1 are given by the following equations as a function of mole fraction (x _Fe,x _Al): 1 $$\begin{gathered} 0< \chi _{A1}< 0.4 \hfill \\ ln \gamma _{Fe} = - 4.511 ( \pm 0.008)\chi _{A1}^2 \hfill \\ ln \gamma _{A1} = - 4.462 ( \pm 0.029)\chi _{Fe}^2 + 0.325( \pm 0.013) \hfill \\ 0.6< \chi _{A1}< 1.0 \hfill \\ ln \gamma _{Fe} = - 4.065 ( \pm 0.006)\chi _{A1}^2 + 0.099( \pm 0.003) \hfill \\ ln \gamma _{A1} = - 4.092 ( \pm 0.026)\chi _{Fe}^2 + 0.002( \pm 0.001) \hfill \\ \end{gathered} $$ The results showed good agreement with those obtained from previous investigations at other temperatures by extrapolation of the activity data to 1573 K.     

Fatigue life and twinning in alpha-zirconium

Two grades of polycrystalline α-Zr containing ~0.003 and ~0.0775 wt pct O have been fatigued in tension-compression about a zero mean load at a frequency of 100 cps at room-temperature. A combined metallographic and microbeam X-ray pole-loci analysis has revealed the presence of {10•12}, {11−21}, and {11•22} twins and {1O−10} slip. In grains completely enclosed by surrounding material fatigue damage has been found in association with 11•21 twins and very occasionally with {11−22} twins but not with 10•12 twins. A further quantitative interpretation has shown that there is a critical resolved shear stress for {11−21} twinning of ~0.5 kg mm⁻² in zirconium containing 0.003 wt pct O. During observations confined to internal grains it was found that increasing grain size and decreasing oxygen content favored the formation of fatigue damage in association with these {11−21} twins. In external grains the fatigue damage was mainly in the form of edge cracks emanating from the specimen surface. The most appropriate criterion for the formation of damage in {11−2l} twin-matrix interfaces appears to be the attainment of a critical resolved shear stress in the {11−21} twinning plane in the (11−26) twinning direction. Formerly with the Department of Physical Metallurgy and Science of Materials, The University, Birmingham, England