Plastic-Strain-Amplitude Dependence of Dislocation Structures in Cyclically Deformed 〈112〉-Oriented Cu-7 at. pct Al Alloy Single Crystals

Dislocation structures in \( [\overline{1} 12] \) Cu-7 at. pct Al alloy single crystals cyclically deformed at different plastic strain amplitudes were investigated by transmission electron microscope (TEM) and compared with the results of \( [\overline{1} 12] \) Cu single crystals. It is found that the plastic strain amplitude γ _pl has an obvious effect on the slip deformation mode, and consequently on the cyclic hardening behavior of \( [\overline{1} 12] \) Cu-7 at. pct Al alloy single crystals with an intermediate stacking fault energy. For instance, a high slip planarity (i.e., only formation of planar-slip bands) contributes to the occurrence of a gentle cyclic hardening with a much lower saturation stress at a low γ _pl of 4.5 × 10^?4. A mixed planar/wavy-slip mode (e.g., persistent Lüder’s bands/wall-like microstructures) at an intermediate γ _pl of 2.2 × 10^?3 causes an obvious cyclic hardening up to a comparable saturation stress to that for the \( [\overline{1} 12] \) Cu single crystal. In contrast, the deformation mode is dominated by wavy slip (e.g., ill-defined dislocation cells and walls) at the highest γ _pl of 7.2 × 10^?3, causing that its cyclic hardening curve is quite similar to that for the \( [\overline{1} 12] \) Cu single crystal; in this case, a slightly higher saturation stress level than that for the Cu single crystal is reached due to the additional solid solution strengthening.     

Texture Development in a Friction Stir Lap-Welded AZ31B Magnesium Alloy

The present study was aimed at characterizing the microstructure, texture, hardness, and tensile properties of an AZ31B-H24 Mg alloy that was friction stir lap welded (FSLWed) at varying tool rotational rates and welding speeds. Friction stir lap welding (FSLW) resulted in the presence of recrystallized grains and an associated hardness drop in the stir zone (SZ). Microstructural investigation showed that both the AZ31B-H24 Mg base metal (BM) and SZ contained β-Mg₁₇Al₁₂ and Al₈Mn₅ second phase particles. The AZ31B-H24 BM contained a type of basal texture (0001)〈11 \( \overline{2} \) 0〉 with the (0001) plane nearly parallel to the rolled sheet surface and 〈11 \( \overline{2} \) 0〉 directions aligned in the rolling direction. FSLW resulted in the formation of another type of basal texture (0001)〈10 \( \overline{1} \) 0〉 in the SZ, where the basal planes (0001) became slightly tilted toward the transverse direction, and the prismatic planes (10 \( \overline{1} \) 0) and pyramidal planes (10 \( \overline{1} \) 1) exhibited a 30 deg + (n ? 1) × 60 deg rotation (n = 1, 2, 3, …) with respect to the rolled sheet normal direction, due to the shear plastic flow near the pin surface that occurred from the intense local stirring. With increasing tool rotational rate and decreasing welding speed, the maximum intensity of the basal poles (0001) in the SZ decreased due to a higher degree of dynamic recrystallization that led to a weaker or more random texture. The tool rotational rate and welding speed had a strong effect on the failure load of FSLWed joints. A combination of relatively high welding speed (20 mm/s) and low tool rotational rate (1000 rpm) was observed to be capable of achieving a high failure load. This was attributed to the relatively small recrystallized grains and high intensity of the basal poles in the SZ arising from the low heat input as well as the presence of a small hooking defect.     

On the Ductility of Magnesium Single Crystals at Ambient Temperature

Magnesium single crystals were loaded in plane-strain compression at ambient temperature, parallel, and normal to the c-axis. In the latter configuration, compression was applied along the 〈 \( 11\overline{2}0 \) 〉 as well as 〈 \( 10\overline{1}0 \) 〉 directions, whereby extension was confined to the c-axis owing to the plane-strain geometry. Out of the three tested orientations, only specimens compressed along the 〈 \( 11\overline{2}0 \) 〉 axis were able to deform up to a remarkable strain of ?1 demonstrating a surprisingly high ductility for pure magnesium at ambient temperature. The other two specimen orientations have depicted failure at two different low strains. The final microstructure of the ductile specimen was a polycrystalline mix of large deformed grains adjoining recrystallized regions of much finer grains, developed by means of extensive dynamic recovery. The corresponding final texture was relatively weak, and showed two orientation peaks with appreciable scatter around them.     

Effect of Multi-Scale Thermoelectric Magnetic Convection on Solidification Microstructure in Directionally Solidified Al-Si Alloys Under a Transverse Magnetic Field

The influence of a transverse magnetic field (B < 1 T) on the solidification structure in directionally solidified Al-Si alloys was investigated. Experimental results indicate that the magnetic field caused macrosegregation, dendrite refinement, and a decrease in the length of the mushy zone in both Al-7 wt pct Si alloy and Al-7 wt pct Si-1 wt pct Fe alloys. Moreover, the application of the magnetic field is capable of separating the Fe-rich intermetallic phases from Al-7 wt pct Si-1 wt pct Fe alloy. Thermoelectric magnetic convection (TEMC) was numerically simulated during the directional solidification of Al-Si alloys. The results reveal that the TEMC increases to a maximum ( \( u_{\rm{max} } \) ) when the magnetic field reaches a critical magnetic field strength ( \( B_{\rm{max} } \) ), and then decreases as the magnetic field strength increases further. The TEMC exhibits the multi-scales effects: the \( u_{\rm{max} } \) and \( B_{\rm{max} } \) values are different at various scales, with \( u_{\rm{max} } \) decreasing and \( B_{\rm{max} } \) increasing as the scale decreases. The modification of the solidification structure under the magnetic field should be attributed to the TEMC on the sample and dendrite scales.     

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.     

First Order Pyramidal Slip of 1/3\ \langle 1\bar{2}10\rangle Screw Dislocations in Zirconium

Atomistic simulations, based either on an empirical interatomic potential or on ab initio calculations, are used to study the pyramidal glide of a \(1/3\ \langle 1\bar{2}10\rangle \) screw dislocation in hexagonal close-packed zirconium. Generalized stacking fault calculations reveal a metastable stacking fault in the first order pyramidal \(\lbrace 10\bar{1}1 \rbrace \) plane, which corresponds to an elementary pyramidal twin. This fault is at the origin of a metastable configuration of the screw dislocation in zirconium, which spontaneously appears when the dislocation glides in the pyramidal plane.     

Anomalous Strain Rate Sensitivity of \{ 10\overline{1}2\} \langle 10\overline{1}\overline{1}\rangle Twinning in a Magnesium Alloy at High Temperature

Anomalous strain rate sensitivity of $ \{ 10\overline{1} 2\} $ { 10 1 ¯ 2 } $ \langle 10\overline{1}\overline{1}\rangle $ 〈 10 1 ¯ 1 ¯ 〉 twinning was observed in a Mg-Al-Mn magnesium alloy during extrusion around 723 K (450 °C). The density of $ \{ 10\overline{1}2\} $ { 10 1 ¯ 2 } $ \langle 10\overline{1}\overline{1}\rangle $ 〈 10 1 ¯ 1 ¯ 〉 twins decreases as the ram speed increases. At 10 mm min^?1, relatively high density twins are activated, but much fewer twins were observed at 30 mm min^?1; at 50 mm min^?1, twins were hardly seen. The negative strain rate sensitivity was ascribed to the interaction of $ \{ 10\overline{1}2\} $ { 10 1 ¯ 2 } $ \langle 10\overline{1}\overline{1}\rangle $ 〈 10 1 ¯ 1 ¯ 〉 twinning with defects.     

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.     

Effect of temperature and shear direction on yield stress by {11\bar 22}〈\overline {11} 23〉 slip in HCP metals23〉 slip in HCP metals

The yield shear stress τ _y due to {11 $\bar 2$ 2}〈 $\overline {11} $ 23〉 second-order pyramidal slip system in cadmium, zinc, and magnesium hcp crystals increased with increasing temperature. This result is interpreted by two thermally activated processes as follows: (1) the dissociation of a (c+a) edge dislocation with a Burgers vector of 1/3〈 $\overline {11} $ 23〉 into a c sessile dislocation and an a glissile basal dislocation, and the subsequent immobilization of the (c+a) edge dislocation; (2) consequently, the double-cross slip of (c+a) screw dislocations must be activated thermally by an increment of applied stress to increase propagation velocity of slip band width. Moreover, τ _y is affected strongly by a direction of applied shear force due to second-order pyramidal slip in zinc as well as in cadmium. The anomalous behaviors of yielding would be caused by the nonsymmetrical core structure of the (c + a) dislocation due to the lattice heterogeneity in hcp metals.     

Predicting the Effect of Mo,Ni, and Si on the Bainitic Stasis

The “transformation stasis” phenomenon during the isothermal bainitic ferrite formation in a series of Fe-C-X (X = Mo, Ni, Si ) alloys has been analyzed. Both the Gibbs energy balance (GEB) approach and the \(T_0\) model have been applied to model the “transformation stasis” phenomenon, and their predictions are compared with experimental results. The \(T_0\) model failed in predicting the transformation stasis (TS) phenomenon for the alloys investigated here, while the GEB predictions are in very good agreement with experimental data. It is found that Mo has a very strong effect on the TS phenomenon, while the effect of Si is found to be negligible. Ni has an intermediate effect.     

Effect of Environment on Fatigue Crack Wake Dislocation Structure in Al-Cu-Mg

Fatigue-induced dislocation structure was imaged at the crack surface using transmission electron microscopy (TEM) of focused ion beam (FIB)-prepared cross sections of naturally aged Al-4Cu-1.4Mg stressed at a constant stress intensity range (7?MPa??m) concurrent with either ultralow (~10^?8?Pa?s) or high-purity (50?Pa?s) water vapor exposure at 296?K (23?°C). A 200-to-600-nm-thick recovered-dislocation cell structure formed adjacent to the crack surface from planar slip bands in the plastic zone with the thickness of the cell structure and slip bands decreasing with increasing water vapor exposure. This result suggested lowered plastic strain accumulation in the moist environment relative to the vacuum. The previously reported fatigue crack surface crystallography is explained by the underlying dislocation substructure. For a vacuum, $ \left\{ { 1 1 1} \right\} $ facets dominate the crack path from localized slip band cracking without resolvable dislocation cells, but cell formation causes some off- $ \left\{ { 1 1 1} \right\} $ features. With water vapor present, the high level of hydrogen trapped within the developed dislocation structure could promote decohesion manifest as either low-index $ \left\{ { 100} \right\} $ or $ \left\{ { 1 10} \right\} $ facets, as well as high-index cracking through the fatigue-formed subgrain structure. These features and damage scenario provide a physical basis for modeling discontinuous environmental fatigue crack growth governed by both cyclic strain range and maximum tensile stress.     

Stress-strain behavior and the dislocation structure at small strains in iron deformed in tension,torsion and combined tension-torsion

Commercial iron specimens of 40 μm grain size were deformed to small strains in tension, torsion and combined tension-torsion at 300 K and the resulting dislocation structures, distributions and densities determined using transmission electron microscopy. Employing the von Mises yield criterion and the total plastic-work hypothesis, good agreement was obtained for the three testing conditions for: a) equivalent stress vs equivalent strain curves, b) the dislocation structure, distribution and densityρ as a function of and c) as a function ofρ ^1/2. Furthermore, upon comparing the vsρ ^1/2 curve for polycrystalline iron with theτ _RSS vsρ ^1/2 curve for single crystals of polyslip orientations, it appears that the theoretical value of 2.9 for the average Taylor factor for bcc metals is appropriate. Almost equally good correlations were obtained on the basis of maximum shear strain and therefore a positive decision between the von Mises andτ _max-γ _ρ ^max yield criteria could not be made. A single test in which the direction of straining in torsion was reversed yielded a density and distribution of dislocations (and a corresponding value of ) equivalent to that developed at a smaller strain in unidirectional straining. Formerly with the Department of Metallurgical Engineering and Materials Science, University of Kentucky, Lexington, Ky. Formerly with the Department of Metallurgical Engineering and Materials Science, University of Kentucky, Lexington, Ky.     

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).$      

Effects of Cooling Rate and Solute Content on the Grain Refinement of Mg-Gd-Y Alloys by Aluminum

The effect of Al additions on grain refinement of Mg-Gd-Y alloys with different solute contents at different cooling rates has been investigated. For all alloys, significant grain refinement was due to the formation of Al₂(Gd _x Y_1?x ) nucleant particles. The number density and size distribution of Al₂(Gd _x Y_1?x ) were affected by both solute content and the cooling rate. Grain sizes (d _gs) of Mg-Gd-Y base alloys and of Mg-Gd-Y-Al alloys were related to solute content (defined by the growth restriction factor, Q), cooling rate ( \( \dot{T} \) ), and area number density (ρ _ns) and size (d _p) of nucleant particles that can be activated. It is found that grain sizes of Mg-Gd-Y base alloys follow the relationship \( d_{\text{gs}} = a + \frac{b}{{Q\sqrt {\dot{T}} }} \) , while grain sizes of Al-refined samples follow the relationship \( d_{\text{gs}} = \frac{a'}{{\sqrt {\rho {}_{\text{ns}}} }} + \frac{b'}{{\sqrt {\dot{T}} Qd_{\text{p}} }} \) , where a, b, a′, and b′ were constants. In addition, the grain refinement effect of Al additions was more susceptible to solute content and the cooling rate than that of Zr which is regarded as the most efficient grain refiner for Mg alloys.     

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.     

Inhomogeneity of plastic flow in constrained deformation

Crystals of copper, Cu+6 wt pct Al, and Ag+4 wt pct Sn were compressed along [111] with flow restricted to [ \(\bar 1\bar 12\) ]. After deformation, four differently oriented regions were observed. Their origin is explained by the instability of the (111)[ \(\bar 1\bar 12\) ] orientation which can rotate to either (112) \(\bar 1\bar 11\) or (110)[001] during the imposed shape change. The direction of rotation is determined by which of two initially equally favored pairs of slip systems operate. Surface friction produces shear stresses which favor one pair over the other (depending on the sign of the shear stress) and thus one of the final orientations. Since the sign of the frictional stress varies systematically with position in the deforming crystal, a systematic variation of orientation results. Another orientation (001)[110] has also been observed to behave similarly. During rolling, the frictional forces drawing the crystal into the roll gap are also expected to lead to the division of the crystal into two misoriented regions. The predictions are generalized to include bcc metals of ( \(\bar 1\bar 12\) )[111] and (110)[001] orientations. Previously reported observations of rolled crystals of FeNi₃, Fe-3.5 pct Si, and Fe-2 pct Al are in accord with the present analysis.     

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.     

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.     

Hydrogen Solubility in Pd/V2O5 Composites Formed by Internal Oxidization and Hydrogen Isotherms in Un-oxidized Pd-V Alloys

Pd-V alloys were internally oxidized (IOed) resulting in composites of nano-particle V₂O₅ precipitates within Pd matrices. These composites were found to interact with H₂ to form hydrogen bronzes, H _x V₂O₅, within the Pd matrix where x can vary between 1.65 and 2.20. Relative partial molar enthalpies for H intercalation into the H-bronze within the Pd/V₂O₅ composite were measured calorimetrically as a function of the H content of the bronze, and these molar enthalpies decrease in magnitude from about ?75 to ?20 kJ/mol H as the H content increases. H₂ isotherms have also been measured in disordered, fcc Pd_0.96V_0.04, Pd_0.945V_0.055, and Pd_0.93V_0.07 alloys from 273 K to 343 K (0 °C to 70 °C). Thermodynamic data have been derived from these isotherms. The relative partial molar enthalpies at infinite dilution of H, $\Updelta H_{\hbox{H}}^\circ,$ increase with atom fraction V, X $_{\hbox{V}},$ while the corresponding standard partial molar entropies, $\Updelta \hbox{S}_{\hbox{H}}^\circ,$ decrease with $\hbox{X}_{\hbox{V}}.$ The first-order term, g₁, in a polynomial expansion of the excess or non-ideal chemical potential of H in r = H-to-metal, mol ratio, decreases in magnitude with $\hbox{X}_{\hbox{V}}$ at a given temperature.