Effect of Tungsten on Primary Creep Deformation and Minimum Creep Rate of Reduced Activation Ferritic-Martensitic Steel

Effect of tungsten on transient creep deformation and minimum creep rate of reduced activation ferritic-martensitic (RAFM) steel has been assessed. Tungsten content in the 9Cr-RAFM steel has been varied between 1 and 2 wt pct, and creep tests were carried out over the stress range of 180 and 260 MPa at 823 K (550 °C). The tempered martensitic steel exhibited primary creep followed by tertiary stage of creep deformation with a minimum in creep deformation rate. The primary creep behavior has been assessed based on the Garofalo relationship, \( \varepsilon = \varepsilon_{\text{o}} + \varepsilon_{\text{T}} [1-\exp (-r^{\prime} \cdot t)] + \dot{\varepsilon }_{\text{m}} \cdot t \) , considering minimum creep rate \( \dot{\varepsilon }_{\text{m}} \) instead of steady-state creep rate \( \dot{\varepsilon }_{\text{s}} \) . The relationships between (i) rate of exhaustion of transient creep r′ with minimum creep rate, (ii) rate of exhaustion of transient creep r′ with time to reach minimum creep rate, and (iii) initial creep rate \( \dot{\varepsilon }_{\text{i}} \) with minimum creep rate revealed that the first-order reaction-rate theory has prevailed throughout the transient region of the RAFM steel having different tungsten contents. The rate of exhaustion of transient creep r′ and minimum creep rate \( \dot{\varepsilon }_{\text{m}} \) decreased, whereas the transient strain ? _T increased with increase in tungsten content. A master transient creep curve of the steels has been developed considering the variation of \( \frac{{\left( {\varepsilon - \varepsilon_{\text{o}} } \right)}}{{\varepsilon_{\text{T}} }} \) with \( \frac{{\dot{\varepsilon }_{\text{m}} \cdot t}}{{\varepsilon_{\text{T}} }} \) . The effect of tungsten on the variation of minimum creep rate with applied stress has been rationalized by invoking the back-stress concept.     

Nonmetallic inclusions in 13XΦA steel for reliable oil-line pipe

Nonmetallic inclusions in low-alloy 13XΦA steel mass-produced at OAO Severskii Trubnyi Zavod are studied. Corrosive nonmetallic inclusions of two types, identified by etching, are found to consist of two phases: MgO · Al₂O₃; and CaS with some quantity of Mn. The orientations identified are \(\{ 111\} _{CaS} \left\| {\{ 110\} _{MgO \cdot Al_2 O_3 } } \right.\) and \(\left\langle {1\bar 10} \right\rangle _{CaS} \left\| {\left\langle {1\bar 11} \right\rangle _{MgO \cdot Al_2 O_3 } } \right.\) .     

Crystallographic orientation relationships among η-Ni3Ti precipitate,reverted austenite,and martensitic matrix in Fe-10Cr-10Ni-2W maraging alloy

The precipitation and reversion behavior in Fe-10Cr-10Ni-2W maraging alloy during aging treatment were investigated. The fine rod-shaped η-Ni₃Ti phases were observed to be precipitated having two specific orientation relationships, termed as type I and type II orientation relationships, with martensitic matrix. The reverted austenite phases were also observed, in addition to η-Ni₃Ti precipitates which have two specific orientation relationships known as Kurdjumov-Sachs (K-S) orientation relationship and Nishiyama-Wassermann (N-W) orientation relationship, with the martensitic matrix during aging at a temperature above 550 ?C. By analyzing the observed electron diffraction patterns and computer-simulated electron diffraction patterns, unified orientation relationships among the martensitic matrix, η-Ni₃Ti precipitate, and reverted austenite phase were suggested. Two types of unified orientation relationships, named as K-S type and N-W type, were found to coexist as follows: $$K - S{\mathbf{ }}type:{\mathbf{ }}(100)_{\alpha '} ||(00 \cdot 1)_{\eta ^1 } ||(111)_\gamma ;{\mathbf{ }}[1\bar 11]_{\alpha '} ||[11 \cdot 0]_{\eta ^1 } ||[10\bar 1]_\gamma $$ $$N - W{\mathbf{ }}type:{\mathbf{ }}(100)_{\alpha '} ||(00 \cdot 1)_{\eta ^2 } ||(\bar 111)_\gamma ;{\mathbf{ }}[001]_{\alpha '} ||[2\bar 1 \cdot 0]_{\eta ^2 } ||[0\bar 11]_\gamma $$      

Fabrication and Characterization of Naturally Selected Epitaxial Fe-{111} Y2Ti2O7 Mesoscopic Interfaces: Some Potential Implications to Nano-Oxide Dispersion-Strengthened Steels

The smallest features of ≈2 to 3 nm in nanostructured ferritic alloys (NFA), a variant of oxide dispersion-strengthened steels, include the Y₂Ti₂O₇ complex oxide cubic pyrochlore phase. The interface between the bcc Fe-Cr ferrite matrix and the fcc nanometer-scale Y₂Ti₂O₇ plays a critical role in the stability, strength, and damage tolerance of NFA. To complement other characterization studies of the actual nanofeatures (NF) themselves, mesoscopic interfaces were created by electron beam deposition of a thin Fe layer on a 5 deg miscut {111} Y₂Ti₂O₇ bulk single crystal surface. While the mesoscopic interfaces may differ from those of the embedded NF, the former facilitate characterization of controlled interfaces, such as interactions with point defects and helium. The Fe-Y₂Ti₂O₇ interfaces were studied using scanning electron microscopy, including electron backscatter diffraction, atomic force microscopy, X-ray diffraction, and transmission electron microscopy (TEM). The polycrystalline Fe layer has two general orientation relationships (OR) that are close to (a) the Nishiyama–Wasserman (NW) OR $ \left\{ {110} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 110 Fe | | 111 Y 2 Ti 2 O 7 and $ \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 110 Y 2 Ti 2 O 7 and (b) $ \left\{ {100} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 111 Y 2 Ti 2 O 7 and $ \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} $ 100 Fe | | 110 Y 2 Ti 2 O 7 . High-resolution TEM shows that the NW interface is near-atomically flat, while the {100}_Fe grains are an artifact associated with a thin oxide layer. However, the fact that there is still a Fe-Y₂Ti₂O₇ OR is significant. No OR is observed in the presence of a thicker oxide layer.     

Reaction Mechanism and Kinetics of Enargite Oxidation at Roasting Temperatures

Roasting of enargite (Cu₃AsS₄) in the temperature range of 648?K to 898?K (375?°C to 625?°C) in atmospheres containing variable amounts of oxygen has been studied by thermogravimetric methods. From the experimental results of weight loss/gain data and X-ray diffraction (XRD) analysis of partially reacted samples, the reaction mechanism of the enargite oxidation was determined, which occurred in three sequential stages:

1. $4{\text{Cu}}_{ 3} {\text{AsS}}_{ 4} \left( {\text{s}} \right){\text{ + 13O}}_{ 2} \left( {\text{g}} \right){\text{ = As}}_{ 4} {\text{O}}_{ 6} \left( {\text{g}} \right){\text{ + 6Cu}}_{ 2} {\text{S}}\left( {\text{s}} \right){\text{ + 10SO}}_{ 2} \left( {\text{g}} \right) $
2. $ 6{\text{Cu}}_{ 2} {\text{S}}\left( {\text{s}} \right){\text{ + 9O}}_{ 2} \left( {\text{g}} \right){\text{ = 6Cu}}_{ 2} {\text{O}}\left( {\text{s}} \right){\text{ + 6SO}}_{ 2} \left( {\text{g}} \right) $
3. $ 6{\text{Cu}}_{ 2} {\text{O}}\left( {\text{s}} \right){\text{ + 3O}}_{ 2} \left( {\text{g}} \right){\text{ = 12CuO}}\left( {\text{s}} \right) $

The three reactions occurred sequentially, each with constant rate, and they were affected significantly by temperature and partial pressure of oxygen. The kinetics of the first stage were analyzed by using the model X?=?k ₁ t. The first stage reaction was on the order of 0.9 with respect to oxygen partial pressure and the activation energy was 44?kJ/mol for the temperature range of 648?K to 898?K (375?°C to 625?°C).     

Plastic deformation of titanium at elevated temperatures

The deformation of iodide titanium single crystals containing 200 to 250 ppm O, was studied in compression at temperatures from 25° to 800°C. Reduction of about 5 pct along thec axis was accommodated almost entirely by \(\left\{ {11\bar 22} \right\}\) twinning from 25° to 300°C, and above 400°C by \(\left\{ {10\bar 11} \right\}\) twinning in combination with c+a slip. The stress for \(\left\{ {11\bar 22} \right\}\) twinning increased with increasing temperature, and twin formation was accompanied by a load drop, while the stress for \(\left\{ {10\bar 11} \right\}\) twinning decreased with increasing temperature and twinning was not accompanied by a load drop. Crystals reduced normal to thec axis deformed by a combination of prism slip and \(\left\{ {10\bar 12} \right\}\) twinning at 25°C and by prism slip alone above 500°C.     

Effect of Slag Composition on the Concentration of Al2O3 in the Inclusions in Si-Mn-killed Steel

The thermodynamic equilibria between CaO-Al₂O₃-SiO₂-CaF₂-MgO(-MnO) slag and Fe-1.5 mass pct Mn-0.5 mass pct Si-0.5 mass pct Cr melt was investigated at 1873 K (1600 °C) in order to understand the effect of slag composition on the concentration of Al₂O₃ in the inclusions in Si-Mn-killed steels. The composition of the inclusions were mainly equal to (mol pct MnO)/(mol pct SiO₂) = 0.8(±0.06) with Al₂O₃ content that was increased from about 10 to 40 mol pct by increasing the basicity of slag (CaO/SiO₂ ratio) from about 0.7 to 2.1. The concentration ratio of the inclusion components, \( {{X_{{{\text{Al}}_{2} {\text{O}}_{3} }} \cdot X_{\text{MnO}} } \mathord{\left/ {\vphantom {{X_{{{\text{Al}}_{2} {\text{O}}_{3} }} \cdot X_{\text{MnO}} } {X_{{{\text{SiO}}_{2} }} }}} \right. \kern-0pt} {X_{{{\text{SiO}}_{2} }} }} \) , and the activity ratio of the steel components, \( {{a_{\text{Al}}^{2} \cdot a_{\text{Mn}} \cdot a_{\text{O}}^{2} } \mathord{\left/ {\vphantom {{a_{\text{Al}}^{2} \cdot a_{\text{Mn}} \cdot a_{\text{O}}^{2} } {a_{\text{Si}} }}} \right. \kern-0pt} {a_{\text{Si}} }} \) , showed a good linear relationship on a logarithmic scale, indicating that the activity coefficient ratio of the inclusion components, \( {{\gamma_{{{\text{SiO}}_{2} }}^{i} } \mathord{\left/ {\vphantom {{\gamma_{{{\text{SiO}}_{2} }}^{i} } {\left( {\gamma_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{i} \cdot \gamma_{\text{MnO}}^{i} } \right)}}} \right. \kern-0pt} {\left( {\gamma_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{i} \cdot \gamma_{\text{MnO}}^{i} } \right)}} \) , was not significantly changed. From the slag-steel-inclusion multiphase equilibria, the concentration of Al₂O₃ in the inclusions was expressed as a linear function of the activity ratio of the slag components, \( {{a_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{s} \cdot a_{\text{MnO}}^{s} } \mathord{\left/ {\vphantom {{a_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{s} \cdot a_{\text{MnO}}^{s} } {a_{{{\text{SiO}}_{2} }}^{s} }}} \right. \kern-0pt} {a_{{{\text{SiO}}_{2} }}^{s} }} \) on a logarithmic scale. Consequently, a compositional window of the slag for obtaining inclusions with a low liquidus temperature in the Si-Mn-killed steel treated in an alumina ladle is recommended.     

Crystallographic Orientation of the ε → α′ Martensitic (Athermal) Transformation in a FeMnAlSi Steel

The presence of athermal ε- and α-martensite (α′) in the as-cast structure of a Fe-0.08C-1.95Si-15.1Mn-1.4Al-0.017N alloy has been revealed by electron backscattered diffraction analysis. The alloy exhibited two athermal martensitic transformations described by γ → α′ and γ → ε → α′. The Shoji–Nishiyama orientation relationship was observed between γ-austenite and ε-martensite, while α-martensite nucleated from γ-austenite exhibited a Kurdjumov–Sachs orientation relationship. Six crystallographic variants of α-martensite consisting of three twin-related variant pairs were observed in ε-bands. A planar parallelism of {0001}ε || {110}α′ and a directional relation of \( \left\langle {1\bar{1} 1} \right\rangle \alpha ' \) lying within 1 deg of \( \left\langle {\bar{1} 2\bar{1} 0} \right\rangle \varepsilon \) existed for these variants.     

The thermodynamic properties of liquid Fe−Si alloys

The thermodynamic properties of liquid Fe?Si alloys have been determined electrochemically by use of the following galvanic cells: $$\begin{gathered} Cr - Cr_2 O_3 (s)|ZrO_2 (CaO)|Fe - Si(l), SiO_2 (s) \hfill \\ Cr - Cr_2 O_3 (s)|ThO_2 (Y_2 O_3 )|Fe - Si(l), SiO_2 (s) \hfill \\ \end{gathered} $$ The free energy of formation of SiO₂ was measured and is ?139.0 and ?134.3 kcals per mole at 1500° and 1600°C, respectively. The activity coefficients of iron and silicon for the atom fraction of siliconN _Si<0.35 at 1600° and 1500°C can be represented by the quadratic formalism. $$\begin{gathered} \left. {\begin{array}{*{20}c} {log \gamma _{Fe} = - 2.12 N_{Si}^2 } \\ {log \gamma _{Si} = - 2.12 N_{Fe}^2 - 0.22} \\ \end{array} } \right\}1600^ \circ C (2912^ \circ F) \hfill \\ \left. {\begin{array}{*{20}c} {log \gamma _{Fe} = - 2.50 N_{Si}^2 } \\ {log \gamma _{Si} = - 2.50 N_{Fe}^2 - 0.13} \\ \end{array} } \right\}1500^ \circ C (2732^ \circ F) \hfill \\ \end{gathered} $$ The results indicate that an excess stability peak occurs at about the equimolar composition. Combining the heats of solution determined in this study with previous data indicates that the heats also follow the quadratic formalism. The partial molar heats, \(\bar L_{Si} \) and \(\bar L_{Fe} \) , are represented by $$\begin{gathered} \bar L_{Si} = - 31 N_{Fe}^2 - 4 kcals per mole \hfill \\ \bar L_{Fe} = - 31 N_{Si}^2 kcals per mole \hfill \\ \end{gathered} $$ ForN _Si less than 0.35 and by $$\begin{gathered} \bar L_{Si} = - 22 N_{Fe}^2 \hfill \\ \bar L_{Fe} = - 22 N_{Fe}^2 - 7.0 \hfill \\ \end{gathered} $$ forN _Fe less than 0.35. There is an inflection point in the transition region similar to an excess stability peak for the excess free energies. At 1600°C the ThO₂(Y₂O₃) electrolyte exhibited insignificant electronic conductivity at oxygen partial pressures as low as that in equilibrium with Si?SiO₂ (2×10^?16 atm).     

Enrichment Mechanism of Phosphate in CaO-SiO2-FeO-Fe2O3-P2O5 Steelmaking Slags

The phosphate-enrichment behavior has experimentally been investigated in CaO-SiO₂-FeO-Fe₂O₃-P₂O₅ steelmaking slags. The reaction ability of structural units in the slags has been represented the mass action concentration \( N_{i} \) from the developed ion and molecule coexistence theory (IMCT)- \( N_{i} \) model based on the IMCT. The defined enrichment possibility \( N_{{{\text{c}}i{\text{ {-}c}}j}} \) and enrichment degree \( R_{{{\text{c}}i{\text{{-}c}}j}} \) of solid solutions containing P₂O₅ from the developed IMCT- \( N_{i} \) model have been verified from the experimental results. The effects of binary basicity, the mass percentage ratio \( {{ ( {\text{pct Fe}}_{t} {\text{O)}}} \mathord{\left/ {\vphantom {{ ( {\text{pct Fe}}_{t} {\text{O)}}} { ( {\text{pct CaO)}}}}} \right. \kern-0pt} { ( {\text{pct CaO)}}}} \) , and mass percentage of P₂O₅ in the initial slags on phosphate-enrichment behavior in the slags has also been discussed. The results show that the P₂O₅ component can easily be bonded by CaO to form tricalcium phosphate 3 CaO·P₂O₅, and the formed 3CaO·P₂O₅ can react with the produced dicalcium silicate 2CaO·SiO₂ to generate solid-solution 2CaO·SiO₂-3CaO·P₂O₅ under fixed cooling conditions. The maximum value of the defined enrichment degree \( R_{{{\text{C}}_{ 2} {\text{S{-}}} {\text{C}}_{ 3} {\text{P}}}} \) of solid-solution 2CaO·SiO₂-3CaO·P₂O₅ is obtained as 0.844 under conditions of binary basicity as 2.5 and the mass percentage ratio \( {{ ( {\text{pct Fe}}_{t} {\text{O)}}} \mathord{\left/ {\vphantom {{ ( {\text{pct Fe}}_{t} {\text{O)}}} { ( {\text{pct CaO)}}}}} \right. \kern-0pt} { ( {\text{pct CaO)}}}} \) as 0.955 at fixed cooling conditions.     

The Solubility and Diffusivity of Fluorine in Solid Copper from Electrochemical Measurements

The solubility and diffusivity of fluorine in solid copper were determined electrochemically using the double solid-state cell $$Ni + NiF_2 \left| {CaF_2 } \right|Cu\left| {CaF_2 } \right|Ni + NiF_2 .$$ In the temperature range 757 to 920°C, the diffusivity of fluorine in solid copper was found to be $$D_F \left( {{{cm^2 } \mathord{\left/ {\vphantom {{cm^2 } s}} \right. \kern-\nulldelimiterspace} s}} \right) = 9.32 \times 10^{ - 2} \exp \left( {\frac{{ - 98,910 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$ . The results obtained for the dissolution of fluorine as atoms in solid copper showed large scatter. However, the equilibrium dissolution of fluorine follows Sieverts’ law. Above the melting point (770°C) of CuF₂, the mean solubility of fluorine in solid copper, for the equilibrium Cu(s)+ CuF ₂(l), follows the relationship $$N_F^s (atom fraction) = 0.98 \exp \left( {\frac{{ - 79,500 {J \mathord{\left/ {\vphantom {J {mole}}} \right. \kern-\nulldelimiterspace} {mole}}}} {{RT}}} \right).$$      

Transmission electron microscopy study on the cross-sectional microstructure of an lon-nitriding layer

The cross-sectional microstructure of an ion-nitrided layer on an A₃ steel (C = 0.15, Si = 0.2, Mn = 0.5, and balance Fe, in wt pct) was studied by transmission electron microscopy (TEM), and its electron diffraction patterns were analyzed. It has been shown that the compound layer consists of columnar ε-Fe_2-3 N and γ-Fe₄N. The former precipitates thin γ-Fe₄N phases related to each other by a 180 deg turning twin, and the orientation relationship between ε-Fe_2-3N and γ-Fe₄N is $$\{ 111\} _{\gamma '} //(0001)_\varepsilon ,\left\langle {1\bar 10} \right\rangle _{\gamma '} //\left\langle {11\bar 20} \right\rangle _\varepsilon $$ The columnar γ′-Fe₄N has a stacking fault substructure and accompanying lattice distortion. There are islandlike ferrite crystals between the columnar crystals. Near the compound layer is mostly γ′-Fe₄N with a coexisting small amount of α-Fe. The diffuse layer is composed of Guinier-Preston (GP) zones, α″-Fe₁₆N₂, γ-Fe₄N, and α-Fe. The γ′-Fe₄N with long period structure considered as the ordering of the stacking fault was found. The characters and transformation mechanism of the case were discussed.     

Resolved shear stress in elastically anisotropic polycrystals

Kneer’s analysis was used to calculate the fraction of a tensile stress applied along the rolling or transverse direction, which is resolved as a shear stress on the various slip systems of an α titanium crystallite as a function of crystallite orientation. The crystallite was assumed to be imbedded in a sheet for which the crystallite orientation distribution had been previously determined. The maximum resolved shear stress was found to increase in the order \(\left\{ {10\bar 10} \right\} - \left\langle {1\bar 210} \right\rangle \) , \(\left\{ {10\bar 11} \right\} - \left\langle {1\bar 210} \right\rangle \) , \(\left\{ {0001} \right\} - \left\langle {1\bar 210} \right\rangle \) in the ratio 1∶1.04∶1.17 for the material studied. This seems to be a direct consequence of single crystal anisotropy, and should be relatively insensitive to changes in crystallite orientation distribution. For a given slip system, the maximum resolved shear stress was found to be higher for a tensile stress applied along the rolling direction than for an equivalent stress along the transverse direction in the ratio 1.04∶1 for the material studied. This is a result of the type of preferred orientation present, which is typical for titanium sheet continuously rolled in the α phase.     

An Insight into Slag Structure from Sulphide Capacities

The molar sulphide capacities $ C_{\text{S}}^{'} $ ?=?(mol?pct?S) ( $ P_{{{\text{O}}_{2} }} /P_{{{\text{S}}_{2} }} $ )^1/2 on four binary systems, MgO-SiO₂, CaO-SiO₂, MnO-SiO₂ and FeO-SiO₂ are elucidated so as to compare the magnitudes of the basicities of four metallic oxides and to estimate the temperature dependencies of the basicities of metallic oxides. The enthalpy changes of the reaction?2O^??=?O?+?O^2?, viz. the silicate polymerization reaction (denoted as $ \Updelta H_{(8)}^{^\circ } $ ) have been calculated from the slopes of the log $ C_{\text{S}}^{'} $ vs 1/T curves for four binary silicates. The $ \Updelta H_{(8)}^{^\circ } $ value is considered in the present work to be an index of the basicity of silicate melts. The basicities obtained on the basis of the $ \Updelta H_{(8)}^{^\circ } $ values are in the order MgO?<?CaO?<?MnO?<?FeO, which are determined by two effects; (i) ionicity of chemical bonds between metallic and oxygen ions and (ii) clustering of metallic oxides in silicates. It is also found that the basicity of the FeO-SiO₂ system is larger at higher temperatures.     

Atomic Structures of [0\bar{1}10] Symmetric Tilt Grain Boundaries in Hexagonal Close-Packed (hcp) Crystals

Molecular dynamics simulation and interface defect theory are used to determine the relaxed equilibrium atomic structures of symmetric tilt grain boundaries (STGBs) in hexagonal close-packed (hcp) crystals with a $ [0\bar{1}10] $ tilt axis. STGBs of all possible rotation angles ?? from 0?deg to 90?deg are found to have an ordered atomic structure. They correspond either to a coherent, defect-free boundary or to a tilt wall containing an array of distinct and discrete intrinsic grain boundary dislocations (GBDs). The STGBs adopt one of six base structures, $ P_{B}^{(i)} $ , i?=?1, ??, 6, and the Burgers vector of the GBDs is related to the interplanar spacing of the base structure on which it lies. The base structures correspond to the basal plane (???=?0?deg, $ P_{B}^{(1)} $ ); one of four minimum-energy, coherent boundaries, $ (\bar{2}111),\;(\bar{2}112),\;(\bar{2}114) $ , and $ (\bar{2}116)\;\left( {P_{B}^{(2)} - P_{B}^{(5)} } \right) $ ; and the $ \left( {11\bar{2}0} \right) $ plane (???=?90?deg, $ P_{B}^{(6)} $ ). Based on these features, STGBs can be classified into one of six possible structural sets, wherein STGBs belonging to the same set i contain the same base boundary structure $ P_{B}^{(i)} $ and an array of GBDs with the same Burgers vector $ b_{\text{GB}}^{(i)} $ , which vary only in spacing and sign with ??. This classification is shown to apply to both Mg and Ti, two metals with different c/a ratios and employing different interatomic potentials in simulation. We use a simple model to forecast the misorientation range of each set for hcp crystals of general c/a ratio, the predictions of which are shown to agree well with the molecular dynamics (MD) simulations for Mg and Ti.     

Correlation Between Viscosity and Electrical Conductivity of Aluminosilicate Melts

The linear relations between logarithm of viscosity and logarithm of electrical conductivity deduced in our previous paper for MO-SiO₂ (M = Mg, Ca, Sr, Ba) and M₂O-SiO₂ (Li, Na, K) melts are extended in this study. It is found that the linear law for MO-SiO₂ system is also followed for the melts of FeO-SiO₂ and MnO-SiO₂ (when electronic conduct can be neglected relative to ionic conduct). The relation between viscosity and electrical conductivity is mainly dependent on the valences of cations of basic oxides. For the $ \sum {{\text{M}}_{x} {\text{O-SiO}}_{2} } $ melt containing several basic oxides, there are two situations: In the case where all cations are divalent (or univalent), the relation is the same as that of MO-SiO₂ melt (or M₂O-SiO₂ melt); in the case of existing both divalent and univalent cations, the coefficients for the linear relation can be calculated based on the coefficients of MO-SiO₂ and M₂O-SiO₂ melts, with the weight factors from the renormalized mole fractions of $ \sum {\text{MO}} $ and $ \sum {{\text{M}}_{ 2} {\text{O}}} $ . It is also found that Al₂O₃ has little effect on the relation, and the law for $ \sum {{\text{M}}_{\text{x}} {\text{O-SiO}}_{ 2} } $ melt can be approximately applied to $ \sum {{\text{M}}_{\text{x}} {\text{O-Al}}_{ 2} {\text{O}}_{ 3} {\text{-SiO}}_{ 2} } $ melt.     

Crystallographic Reconstruction Study of the Effects of Finish Rolling Temperature on the Variant Selection During Bainite Transformation in C-Mn High-Strength Steels

The effect of finish rolling temperature on the austenite-(γ) to-bainite (α) phase transformation is quantitatively investigated in high-strength C-Mn steels using an alternative crystallographic γ reconstruction procedure, which can be directly applied to experimental electron backscatter diffraction mappings. In particular, the current study aims to clarify the respective contributions of the γ conditioning during the hot rolling and the variant selection during the phase transformation to the inherited texture. The results confirm that the sample finish rolled at the lowest temperature [1102 K (829 °C)] exhibits the sharpest transformation texture. It is shown that this sharp texture is exclusively due to a strong variant selection from parent brass {110} \( \left\langle {1\bar{1}2} \right\rangle \) , S {213} \( \left\langle {\bar{3}\bar{6}4} \right\rangle \) and Goss {110}〈001〉 grains, whereas the variant selection from the copper {112} \( \left\langle {\bar{1}\bar{1}1} \right\rangle \) grains is insensitive to the finish rolling temperature. In addition, a statistical variant selection analysis proves that the habit planes of the selected variants do not systematically correspond to the predicted active γ slip planes using the Taylor model. In contrast, a correlation between the Bain group to which the selected variants belong and the finish rolling temperature is clearly revealed, regardless of the parent orientation. These results are discussed in terms of polygranular accommodation mechanisms, especially in view of the observed development in the hot-rolled samples of high-angle grain boundaries with misorientation axes between 〈111〉γ and 〈110〉γ.     

Study of \{ 11\bar{2} 1\} Twinning in α-Ti by EBSD and Laue Microdiffraction

Activity of the $ \{ 11\bar{2} 1\} \langle \bar{1} \bar{1} 26 \rangle $ extension twinning (T2) mode was analyzed in a commercial purity Ti sample after 2 pct tensile strain imposed by four-point bending. The sample had a moderate c-axis fiber texture parallel to the tensile axis. Compared with the many $ \{ 10\bar{1} 2\} \langle \bar{1} 011 \rangle $ extension (T1) twins that formed in 6 pct of the grains, T2 twins were identified in 0.25 pct of the grains by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) maps. Most of the T2 twins exhibited irregular twin boundaries (TBs) on one side of the twin. High-resolution EBSD revealed both intermediate orientations at some matrix/twin interfaces and substantial lattice rotation within some T2 twins. Interactions between matrix 〈c + a〉 dislocations $ \frac{1}{3} \langle 1\bar{2} 13 \rangle $ and a $ \{ 11\bar{2} 1\} $ T2 twin were investigated by combining SEM/EBSD slip trace characterization and Laue microdiffraction peak streak analysis. 〈c + a〉 dislocations that originally glided on a pyramidal plane in the matrix were found on other planes in both the matrix and the twin, which was attributed to extensive cross-slip of the screw component, whose Burgers vector was parallel to the twinning plane. On the other hand, thickening of the twin could engulf some pile-up edge components in front of the TB. During this process, these 〈c + a〉 dislocations transmuted from a pyramidal plane $ (0\bar{1} 11) $ in the matrix to a prismatic plane $ (\bar{1} 010)_{\text{T}} $ in the twin lattice. Finally, possible mechanisms for the nucleation and growth of T2 twins will be discussed.     

A Thermodynamic Model for Representation Reaction Abilities of Structural Units in Fe-S Binary Melts Based on the Atom-Molecule Coexistence Theory

A thermodynamic model for calculating the mass action concentrations of structural units in Fe-S binary melts based on the atom-molecule coexistence theory, i.e., AMCT-N _i model, has been developed and verified through a comparison with the reported activities of both S and Fe in Fe-S binary melts with changing mole fraction $ x_{\text{S}} $ of S from 0.0?to 0.095?at temperatures of 1773?K, 1823?K, and 1873?K (1500 °C, 1550 °C, and 1600 °C) from the literature. The calculated mass action concentration $ N_{\text{S}} $ of S is much smaller than the reported activity $ a_{\text{R, S}} $ of S in Fe-S binary melts with changing mole fraction $ x_{\text{S}} $ of S from 0.0?to 0.095. The calculated mass action concentration $ N_{\text{S}} $ of S can correlate the reliable 1:1?corresponding relationship with the reported activity $ a_{\text{R, S}} $ or $ a_{\%,\text {S}} $ of S through the introduced transformation coefficients with absolutely mathematical meaning or through the defined comprehensive mass action concentration of total S with explicitly physicochemical meaning. The calculated mass action concentrations $ N_{i} $ of structural units from the developed AMCT-N _i thermodynamic model can be applied to describe or predict the reaction abilities of structural units in Fe-S binary melts. The reaction abilities of Fe and S show a competitive relationship each other in Fe-S binary melts in a temperature range from 1773?K to 1873?K (1500 °C to 1600 °C). The calculated mass action concentration $ N_{{{\text{FeS}}_{ 2} }} $ of FeS_2?is very small and can be ignored because FeS_2?can be incongruently decomposed above 1016?K (743 °C). The very small values for the calculated mass action concentrations $ N_{{{\text{FeS}}_{ 2} }} $ of FeS_2?in a range of mole fraction $ x_{\text{S}} $ of S from 0.0?to 1.0?as well as a maximum value for the calculated mass action concentration $ N_{\text{FeS}} $ of FeS with mole fraction $ x_{\text{S}} $ of S as 0.5?are coincident with diagram phase of Fe-S binary melts. A spindle-type relationship between the calculated mass action concentration $ N_{i} $ and the calculated equilibrium mole number $ n_{i} $ can be found for FeS and FeS_2?in Fe-S binary melts. The Raoultian activity coefficient $ \gamma_{S}^{0} $ of S relative to pure liquid S(l) as standard state and the infinitely dilute solution as reference state in Fe-S binary melts can be determined as 1.0045?in a temperature range from 1773?K to 1873?K (1500 °C to 1600 °C). The standard molar Gibbs free energy change $ \Updelta_{\text{sol}} G_{{{\text{m, S }}({\text{l}}) \to [{\text{S}}]_{{ \, [{\text{pct \, S}}] = 1.0}} }}^{{\Uptheta,\%}} $ of dissolving liquid S for forming [pct S] as 1.0?in Fe-S binary melts relative to 1?mass percentage of S as standard state can be formulated as $ \Updelta_{\text{sol}} G_{{{\text{m, S }}({\text{l}}) \to [{\text{S}}]_{{ \, [{\text{pct \, S] }} = \, 1.0}} }}^{{\Uptheta,\, \%}} \,\, = -0.219\,-\,33.70T\,\,\left( {\text{J/mol}} \right).$