Heterogeneous nucleation of pb particles embedded in a Zn matrix

Zinc-10 and 20 wt pct Pb alloys have been rapidly solidified by melt spinning to obtain a very fine scale dispersion of nanometer-sized Pb particles embedded in Zn matrix. The microstructure and crystallography of the Pb particles have been studied using transmission electron microscopy (TEM). Each embedded Pb particle is a single crystal, with a truncated hexagonal biprism shape with the 6/mmm Zn matrix point group symmetry surrounded by and facets. The Pb particles solidify with a well-defined orientation relationship with the Zn matrix of . The melting and solidification behavior of the Pb particle have been studied using differential scanning calorimetry (DSC). The Pb particles solidify with an undercooling of approximately 30 K, by heterogeneous nucleation on the {0001} facets of the surrounding Zn matrix, with an apparent contact angle of 23 deg.     

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.     

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.     

Observations of the Atomic Structure of Tensile and Compressive Twin Boundaries and Twin–Twin Interactions in Zirconium

The boundary structures of twins in the hexagonal close-packed metal zirconium were studied. High-resolution transmission electron microscopy was used to characterize the boundary structure of \(\{10\bar{1}2\}\) (T1), \(\{\bar{1}\bar{1}21\}\) (T2), and \(\{\bar{1}\bar{1}22\}\) (C1) twins on the atomic level. Basal–prismatic (B–P) plane faceting is observed along the T1 twin boundaries, matching previous observations of T1 twins in magnesium. C1 twins are observed to form basal–pyramidal (B–Py) facets along otherwise perfect twin planes. T2 twins exhibit faceting that aligns prism planes with second-order pyramidal planes across the boundary (P–Py facets). As a function of the crystallography, T2 twins appear less likely to accommodate large deviations from perfect twin planes by P–Py faceting alone, and may rely on small dislocation-accommodated facets to achieve arbitrary boundary planes. The structure of these boundaries, specifically the modes by which faceting is permitted, has a direct impact on boundary mobility. In addition, the boundary structure of two C1 twins during a twin–twin interaction event is observed, and is compared to previous observations of tensile twin–twin interactions in magnesium.     

Effects of Interfacial Lattice Mismatching on Wetting of Ni-Plated Steel by Magnesium

In this study, wetting has been characterized by measuring the contact angles of AZ92 Mg alloy on Ni-electroplated steel as a function of temperature. Reactions between molten Mg and Ni led to a contact angle of about 86 deg in the temperature range of 891 K to 1023 K (618 °C to 750 °C) (denoted as Mode I) and a dramatic decrease to about 46 deg in the temperature range of 1097 K to 1293 K (824 °C to 1020 °C) (denoted as Mode II). Scanning and transmission electron microscopy (SEM and TEM) indicated that AlNi + Mg₂Ni reaction products were produced between Mg and steel (Mg-AlNi-Mg₂Ni-Ni-Fe) in Mode I, and just AlNi between Mg and steel (Mg-AlNi-Fe) in Mode II. From high resolution TEM analysis, the measured interplanar mismatches for different formed interfaces in Modes I and II were \( 17{\kern 1pt} \;{\text{pct}}_{{\{ 10\overline 11\}_{\text{Mg}} //\{ 110\}_{\text{AlNi}} }} \)-\( 104.3\;{\text{pct}}_{{\{ 110\}_{\text{AlNi}} //\left\{ {10\overline{1}0} \right\}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} }} \)-\( 114\,{\text{pct}}_{{\left\{ {0003} \right\}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} //\{ 111\}_{\text{Ni}} }} \) and \( 18\,{\text{pct}}_{{\{ 10\overline 11\}_{\text{Mg}} //\{ 110\}_{\text{AlNi}} }} \)-\( 5\,{\text{pct}}_{{\left\{ {110} \right\}_{\text{AlNi}} //\{ 110\}_{\text{Fe}} }} \), respectively. An edge-to-edge crystallographic model analysis confirmed that Mg₂Ni produced larger lattice mismatching between interfaces with calculated minimum interplanar mismatches of \( 16.4\,{\text{pct}}_{{{\text{\{ 10}}\overline 1 1 {\text{\} }}_{\text{Mg}} / / {\text{\{ 110\} }}_{\text{AlNi}} }} \)-\( 108.3\,{\text{pct}}_{{{\text{\{ 110\} }}_{\text{AlNi}} / / {\text{\{ 10}}\overline 1 1 {\text{\} }}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} }} \)-\( 17.2\,{\text{pct}}_{{{\text{\{ 10}}\overline 1 1 {\text{\} }}_{{{\text{Mg}}_{ 2} {\text{Ni}}}} / / {\text{\{ 100\} }}_{\text{Ni}} }} \) for Mode I and \( 16.4\,{\text{pct}}_{{{\text{\{ 10}}\overline1 1 {\text{\} }}_{\text{Mg}} / / {\text{\{ 110\} }}_{\text{AlNi}} }} \)-\( 0.6\,{\text{pct}}_{{{\text{\{ 111\} }}_{\text{AlNi}} / / {\text{\{ 111\} }}_{\text{Fe}} }} \) for Mode II. Therefore, it is suggested that the poor wettability in Mode I was caused by the existence of Mg₂Ni since AlNi was the immediate layer contacting molten Mg in both Modes I and II, and the presence of Mg₂Ni increases the interfacial strain energy of the system. This study has clearly demonstrated that the lattice mismatching at the interfaces between reaction product(s) and substrate, which are not in direct contact with the liquid, can greatly influence the wetting of the liquid.     

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.     

Thermodynamic properties of the Zn−Pb−In ternary system in dilute liquid zinc solutions

Electromotive force measurements were conducted on ternary Zn?Pb?In solutions having zinc concentrationsX _Zn=0.03, 0.05, 0.07, and 0.1. Special attention was paid to the effect of the addition of indium and lead on the Ln γ_Zn value at 714°, 757°, and 805°K. These data served to determine the interaction parameters ∈ _Zn ^In and ∈ _Pb ^Zn from the \((ln\gamma _{Zn} )_{X_{Zn} } \to _0 vs X_{Pb} \) plots over the indicated ranges of temperatures. The end points in ln γ_Zn vs X_Pb and \((ln\gamma _{Zn} )_{X_{Zn} } \to _0 vs X_{Pb} \) plots were taken from previous measurements on the Zn?In and Zn?Pb systems. The values of ln γ_Zn and \((ln\gamma _{Zn} )_{X_{Zn} } \to _0 \) in Zn?Pb?In dilute solutions were carried out by means of Krupkowski’s formulae. The influence of the Zn?Pb system in Zn?Pb-Me ternary solutions with a preponderant content of lead was analyzed whenMe=Bi, Cd, Sn, and Sb.     

Interfaces in MoSi2-SiC In Situ composites synthesized by melt processing

Interfaces between the primary β-SiC and the surrounding MoSi₂ matrix in melt-synthesized in situ composites have been investigated, with emphasis on the chemistry and crystallographic relationships developed during solidification. Primary SiC growth occurs with {002} and {111} facets, both of which are found to template the subsequent nucleation and epitaxial growth of the MoSi₂ matrix. Eight independent orientation relationships (ORs) were identified, involving the following combinations of planes: $$\begin{gathered} \left\{ {002} \right\}_{Sic} \parallel \left( {001} \right)_{MoSi_2 } \left( {3 rotational variants} \right), or \{ 101)_{MoSi_2 } \hfill \\ \left\{ {111} \right\}_{Sic} \parallel (001)_{MoSi_2 } , or \{ 100)_{MoSi_2 } \left( {2 rotational variants} \right),or \{ 101)_{MoSi_2 } \hfill \\ \end{gathered} $$ The interfacial relationships were rationalized using coincident site lattice arguments as well as energetic simulations based on the Grey-Bohr algorithm. The latter analysis suggests that the multiplicity of relationships arises from local effects associated with the size and shape of the adsorbate layers preceding the formation of the MoSi₂ nuclei. An amorphous carbon layer, 2- to 5-nm thick, was detected at all interfaces and some of the matrix grain boundaries. This interphase is believed to evolve by solid-state precipitation of C during postsolidification cooling and is, in principle, metastable. The C interphase enables easy debonding and thus may have important implications for the mechanical performance of materials involving SiC/MoSi₂ constituents.     

Orientation Relationship Between Magnetic Domains and Twins in Ni<Subscript>52</Subscript>Fe<Subscript>17</Subscript>Ga<Subscript>27</Subscript>Co<Subscript>4</Subscript> Magnetic Shape Memory Alloy

The orientation relationship between magnetic domain and twins in the directional solidified Ni₅₂Fe₁₇Ga₂₇Co₄ magnetic shape memory alloy was analyzed by electron backscatter diffraction and magnetic force microscopy. The twin interface plane was determined to be \( \{ \bar{1}10\} \) plates. The magnetic domains walls with a misorientation about 5 deg belong to low angle boundaries. According to the orientation relationship between twins and magnetic domains, the intersection angle on the observed surface can be estimated.     

Confirmation of the Grube-Jedele Procedure in Processing Interdiffusion Data in Binary Alloys

The 1932/1933 experiments of Grube-Jedele (G-J) reveal their discovery that 0–100 at. pct diffusion penetration curves can generate monotone composition-variant interdiffusion coefficients, \( \tilde{D}\left( X \right) \). G-J templated a smoothed infinite couple sectionally and sequentially curve via a set of constant \( \tilde{D} \) error function curves with local 2- and 3-point determined. The first and second derivatives created a monotone sequence of coefficient values. We detail this in processing G-J curves, remarkably revealing as with constant \( \tilde{D} \), that variable \( \tilde{D} \) obtained generates a \(\root{}\of{(t)}\) penetration dependence. This finding was later verified analytically via Ginzburg-Landau’s (G-L) 1950 variational-quantum, lattice-dynamical requirement that \( \tilde{D} \) lies outside the Fickian second derivative. The G-L and G-J procedures and analyses were supported in 1947 by Smigelskas and Kirkendall’s experimental discounting of Boltzmann’s 1897 purely mathematical theorem.     

Distribution Ratios of Phosphorus Between CaO-FeO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Na<Subscript>2</Subscript>O/TiO<Subscript>2</Subscript> Slags and Carbon-Saturated Iron

In order to effectively enhance the efficiency of dephosphorization, the distribution ratios of phosphorus between CaO-FeO-SiO₂-Al₂O₃/Na₂O/TiO₂ slags and carbon-saturated iron (\( L_{\text{P}}^{\text{Fe-C}} \)) were examined through laboratory experiments in this study, along with the effects of different influencing factors such as the temperature and concentrations of the various slag components. Thermodynamic simulations showed that, with the addition of Na₂O and Al₂O₃, the liquid areas of the CaO-FeO-SiO₂ slag are enlarged significantly, with Al₂O₃ and Na₂O acting as fluxes when added to the slag in the appropriate concentrations. The experimental data suggested that \( L_{\text{P}}^{\text{Fe-C}} \) increases with an increase in the binary basicity of the slag, with the basicity having a greater effect than the temperature and FeO content; \( L_{\text{P}}^{\text{Fe-C}} \) increases with an increase in the Na₂O content and decrease in the Al₂O₃ content. In contrast to the case for the dephosphorization of molten steel, for the hot-metal dephosphorization process investigated in this study, the FeO content of the slag had a smaller effect on \( L_{\text{P}}^{\text{Fe-C}} \) than did the other factors such as the temperature and slag basicity. Based on the experimental data, by using regression analysis, \( \log L_{\text{P}}^{\text{Fe-C}} \) could be expressed as a function of the temperature and the slag component concentrations as follows:

$$ \begin{aligned} \log L_{\text{P}}^{\text{Fe-C}} & = 0.059({\text{pct}}\;{\text{CaO}}) + 1.583\log ({\text{TFe}}) - 0.052\left( {{\text{pct}}\;{\text{SiO}}_{2} } \right) - 0.014\left( {{\text{pct}}\;{\text{Al}}_{2} {\text{O}}_{3} } \right) \\ \, & \quad + 0.142\left( {{\text{pct}}\;{\text{Na}}_{2} {\text{O}}} \right) - 0.003\left( {{\text{pct}}\;{\text{TiO}}_{2} } \right) + 0.049\left( {{\text{pct}}\;{\text{P}}_{2} {\text{O}}_{5} } \right) + \frac{13{,}527}{T} - 9.87. \\ \end{aligned} $$

     

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.     

The precipitation of epsilon-carbide in twinned martensite

Tempering of martensite has been investigated by means of thin foil electron microscopy in a high carbon steel, a high nickel steel, and a silicon steel. ε carbide has been unambiguously identified in each steel. It was found that the carbide was precipitated with the Jack orientation relationship: $$\begin{gathered} \left( {0001} \right)_\varepsilon \parallel \left( {011} \right)_{\alpha '} \hfill \\ \left( {10\bar 10} \right)_\varepsilon \parallel \left( {2\bar 11} \right)_{\alpha '} \hfill \\ \end{gathered} $$ In the silicon steel the ε carbide precipitated in the form of needles which grew with a \(\left[ {01\bar 10} \right]_\varepsilon \) close to \(\left[ {21\bar 1} \right]_{\alpha '} \) . This growth direction minimizes the surface energy of the needles, yet allows growth in a direction of low mismatch.     

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.     

On the Prediction of <Emphasis Type="Italic">α</Emphasis>-Martensite Temperatures in Medium Manganese Steels

A new composition-based method for calculating the α-martensite start temperature in medium manganese steel is presented and uses a regular solution model to accurately calculate the chemical driving force for α-martensite formation, \( \Delta G_{\text{Chem}}^{\gamma \to \alpha } \). In addition, a compositional relationship for the strain energy contribution during martensitic transformation was developed using measured Young’s moduli (E) reported in literature and measured values for steels produced during this investigation. An empirical relationship was developed to calculate Young’s modulus using alloy composition and was used where dilatometry literature did not report Young’s moduli. A comparison of the \( \Delta G_{\text{Chem}}^{\gamma \to \alpha } \) normalized by dividing by the product of Young’s modulus, unconstrained lattice misfit squared (δ ²), and molar volume (Ω) with respect to the measured α-martensite start temperatures, \( M_{\text{S}}^{\alpha } \), produced a single linear relationship for 42 alloys exhibiting either lath or plate martensite. A temperature-dependent strain energy term was then formulated as \( \Delta G_{\text{str}}^{\gamma \to \alpha } \left( {{\text{J}}/{\text{mol}}} \right) = E\varOmega \delta^{2} (14.8 - 0.013T) \), which opposed the chemical driving force for α-martensite formation. \( M_{\text{S}}^{\alpha } \) was determined at a temperature where \( \Delta G_{\text{Chem}}^{\gamma \to \alpha } + \Delta G_{\text{str}}^{\gamma \to \alpha } = 0 \). The proposed \( M_{\text{S}}^{\alpha } \) model shows an extended temperature range of prediction from 170 K to 820 K (?103 °C to 547 °C). The model is then shown to corroborate alloy chemistries that exhibit two-stage athermal martensitic transformations and two-stage TRIP behavior in three previously reported medium manganese steels. In addition, the model can be used to predict the retained γ-austenite in twelve alloys, containing ε-martensite, using the difference between the calculated \( M_{\text{S}}^{\varepsilon } \) and \( M_{\text{S}}^{\alpha } \).     

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: $$K - S{\mathbf{ }}type:{\mathbf{ }}(100)_{\alpha '} ||(00 \cdot 1)_{\eta ^1 } ||(111)_\gamma ;{\mathbf{ }}[1\bar 11]_{\alpha '} ||[11 \cdot 0]_{\eta ^1 } ||[10\bar 1]_\gamma $$ $$N - W{\mathbf{ }}type:{\mathbf{ }}(100)_{\alpha '} ||(00 \cdot 1)_{\eta ^2 } ||(\bar 111)_\gamma ;{\mathbf{ }}[001]_{\alpha '} ||[2\bar 1 \cdot 0]_{\eta ^2 } ||[0\bar 11]_\gamma $$      

Twin Interactions in Pure Ti Under High Strain Rate Compression

Twin interactions associated with {11\( \overline{2} \)1} (E2) twins in titanium deformed by high strain rate (~2600 s^?1) compression were studied using electron backscatter diffraction technique. Three types of twins, {10\( \overline{1} \)2} (E1), {11\( \overline{2} \)2} (C1), and {11\( \overline{2} \)4} (C3), were observed to interact with the preformed E2 twins in four parent grains. The E1 variants nucleated at twin boundaries of some E2 variants. And the C3 twins were originated from the intersection of C1 and E2. The selection of twin variant was investigated by the Schmid factors (SFs) and the twinning shear displacement gradient tensors (DGTs) calculations. The results show that twin variants that did not follow the Schmid law were more frequently observed under high strain rate deformation than quasi-static deformation. Among these low-SF active variants, 73 pct (8 out of 11) can be interpreted by DGT. Besides, 26 variants that have SF values close to or higher than their active counterparts were absent. Factors that may affect the twin variant selections were discussed.     

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.     

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 \(\left\langle {1\bar 10} \right\rangle _{CaS} \left\| {\left\langle {1\bar 11} \right\rangle _{MgO \cdot Al_2 O_3 } } \right.\) .