Preferred Orientation Relationship Research Articles

Effect of quenching temperature on the microstructure evolutions and strength-ductility of W-Ni-Cu alloy at room-temperature and cryogenic

Tungsten (BCC phase) exhibits distinct ductile-to-brittle transition characteristics. As temperature decreases, brittleness increases, ductility decreases, significantly limits its engineering applications. Here, W-5Ni-2Cu alloy was prepared by powder metallurgy, and the effect of different quenching temperatures on its microstructure evolution and mechanical properties at room-temperature and cryogenic. According to the results, rapid quenching can significantly improve the strength-ductile of W-5Ni-2Cu, especially the cryogenic properties. After quenching at 1200 °C, the strength-ductility of W-5Ni-2Cu from room temperature to −43 °C did not deteriorate, and compared with the sintered alloy, the tensile strength and elongation were increased by 7.3% and 13.0% at room-temperature, and by 16.0% and 100.0% at cryogenic. The appropriate quenching temperature can effectively refine the W grain size, reducing the WW continuity and dihedral angle, while the quenching temperatures reaches 1300 °C, it will cause abnormal W grain growth and deteriorate the mechanical properties. Furthermore, rapid quenching changes the fracture mode from intergranular fractures to transgranular fractures. Especially, the W- 〈111〉∥γ-〈110〉 preferential orientation relationship is obviously improved at −43 °C, increasing the interfacial bonding strength and co-deformation ability of W-γ phase, thereby slowing down the hardening rate and increasing the strength and elongation.

Effects of forging deformation on variant selection and morphology of α in TiB/near α-Ti composites

The role of forging deformation on α-Ti in TiB/near α-Ti composites is still an unknown area. In the present work, the evolution of the variant selection and morphology of α-Ti was systematically investigated in as-sintered and as-forged TiB/near α-Ti composites through scanning electron microscope and electron back-scattering diffraction analysis. The results indicated that the α lamellae were refined, and their c-axes were either oriented at 45°or perpendicular to the Z-direction after hot forging. Six preferred orientation relationships (ORs) between TiB whiskers and α variants have been quantitatively identified using the misorientation axis-angle pair distribution maps. Compared to the as-sintered sample, the total length of the TiB/α phase boundary with six preferred ORs increased from 5.31% to 9.76% after hot forging. It was found that TiB contributed to the formation of the refined and equiaxed α variants that satisfied the preferred ORs with it. Moreover, an analysis of the reconstructed parent β grains revealed that the α variants heterogeneously nucleated from TiB, which did not satisfy the Burgers orientation relationship (BOR) with the parent β grains.

Partition the total energy of Al3Ti to characterize the Al3Ti/Al interface properties: a first-principles study

The geometric model of coplanar reciprocal lattice points (CRLPs) was used to predict the preferred orientation relationships (ORs) between the Al3Ti intermetallic particle and the Al matrix. The calculation result indicates that there exist two preferred ORs, i.e. (001)Al3Ti//(001)Al, [100]Al3Ti//[100]Al and (010)Al3Ti//(010)Al, [100]Al3Ti//[101¯]Al. The periodic models with a specific interface structure and surface slab models on a particular crystallographic plane were proposed to partition the total energy of the Al3Ti compound into its constituent atoms’ energies. The Ti and two kinds of Al atoms (Wyckoff notation 2b and 4d) possess the energy of -119.80325739 Ry, -5.09778518 Ry, and -5.03677683 Ry, respectively. Compared with the Al3Ti total energy of -269.94919247 Ry, the proposed energy partition scheme presents a satisfactory accuracy better than ∼10−7 Ry. Owing to the data of the atom's energy in the solid state, the definite value of surface energy can be obtained whether or not it is a stoichiometric or non-stoichiometric surface. The interface energy calculation, which was carried out on all the preferred ORs with all the possible atomic configurations, indicates that the energy-preferred interface possesses the orientation relationship of (001)Al3Ti//(001)Al, [100]Al3Ti//[100]Al. The atomic configuration is that the atoms on the surface of the Al slab face directly to atoms on the second layer of the Al3Ti slab with the Al-Ti terminated surface on account of its lowest interface energy of 0.005 J/m2. The predicted OR agrees well with the previously published experimental results, and the significantly lower interface energy explains the potency of the Al3Ti particle as a heterogeneous nucleation site in the aluminum solidification process.

Elucidating the role of precipitated phase particles in modifying creep properties of as-cast Mg-Bi/Sn-based alloys

The study developed the three alloy systems with different precipitates and examined the role of precipitated phase particles in modifying the creep properties of as-cast Mg-10Bi-0.5Mn-0.5Ag (BMQ1000), Mg-5Bi-5Sn-0.5Mn-0.5Ag (BTMQ5500) and Mg-10Sn-0.5Mn-0.5Ag (TMQ1000) alloys at temperatures ranging from 423 to 473 K and stresses of 45–85 MPa. The values of n for the BMQ1000, BTMQ5500, and TMQ1000 alloys were determined as 6.67, 5.75, and 5.92, respectively. Moreover, the activation energy for these alloys was found to be 164.71, 134.68, and 135.93 kJ/mol, respectively. The results suggested that the creep properties followed the order of BTMQ5500 > TMQ1000 > BMQ1000. A coarse and uneven distribution of the Mg3Bi2 precipitated phase in the BMQ1000 alloy leads to a feeble pining effect on dislocation slipping and generates substantial stress concentrations. For TMQ1000 alloy, while the nanoscale Mg2Sn precipitates have a stronger barrier effect on dislocations than the Mg3Bi2 in the BMQ1000 alloy, their ability to inhibit dislocation climbing is comparatively weak. Furthermore, it was found that Mg2Sn precipitates and α-Mg exhibited a preferential orientation relationship of (020)Mg2Sn // (–1010)Mg, and the morphology of the precipitated phase transformed in a way that hinders dislocation movement effectively. In addition, elastic interactions between the precipitated phases are identified. The above-mentioned factors are largely responsible for the notable enhancement in creep resistance. Further, it is ascertained that cross-slip and pyramidal 〈c + a〉 slip are primary creep mechanisms in the BMQ1000 alloy. In contrast, the dominant mechanisms in TMQ1000 and BTMQ5500 alloys are dislocation climb and pyramidal 〈c + a〉 slip. Moreover, stacking faults (SFs) and twinning assist in the creep deformation of the BTMQ5500 alloy.

Study on morphology and interface relationship between Ag3(Sn, In) and Cu6(Sn, In)5

The morphology, orientation and growth relationships of the intermetallic compounds (IMCs) Ag3(Sn, In) and Cu6(Sn, In)5 at the Sn-3.5Ag-0.5Bi-8.0In solder/Cu substrate interface were investigated. The Ag(Sn, In) at the interface is "flower-like". However, when the reflow parameters were changed and the cooling rate was increased, Ag3(Sn, In) had difficulty in nucleation. A preferential orientation relationship between the Ag3(Sn, In) phase and the Cu6(Sn, In)5 substrate was established. An angle of 35° existed between the adjacent Ag3(Sn, In) grains and Cu6(Sn, In)5 grains. In addition, coincident mismatch relationships were found between specific crystallographic planes of Ag3(Sn, In) and Cu6(Sn, In)5. The (001) crystallographic plane of Ag3(Sn, In) and the (0001) crystallographic plane of Cu6(Sn, In)5 have a mismatch of 12.23% and are more likely to form a coherent interface.

Eutectic solidification in Mg-9Al-0.7Zn: From divorced to coupled growth

In hypoeutectic Mg-Al-based alloys, Mg17Al12 forms in the last stages of solidification by a eutectic reaction that is usually fully or partially divorced. Here we investigate the nucleation, growth and morphology of the Mg17Al12-containing eutectic in a multicomponent Mg-9Al-0.7Zn-0.2Mn alloy. Under all solidification conditions studied, Mg17Al12 formed an interconnected skeleton in 3D and Mg17Al12 orientation domains spanned multiple α-Mg grains, indicating that Mg17Al12 nucleation events are relatively infrequent. While most regions of α-Mg+Mg17Al12 had no preferred orientation relationship (OR), occasional eutectic regions had the Burgers OR that may be related to the nucleation of Mg17Al12 on α-Mg during solidification. It is shown that the degree of partially divorced growth depends on a simple geometrical measure for the space available for eutectic growth involving the dendrite arm spacing, the eutectic fraction and the eutectic spacing. We then demonstrate that fully coupled eutectic microstructures can be generated in this alloy by independently manipulating the magnesium dendrite solidification time and the eutectic cooling rate.

Long-term structural stability and excellent mechanical properties of CoCrNi system medium entropy alloys

CoCrNi medium entropy alloys (MEAs) are promising candidates for high- temperature application, but their structural stability and mechanical properties during long-term service are still an open question. This work comprehensively investigated the microstructure and mechanical properties at both room and high temperatures of CoCrNi MEAs after being aged for 500 h at 850 °C. It has been shown that the long-term aged CoCrNi MEA has held a single γ phase, a nanoparticulate and discontinuous block γ′ phase, and η-Ni3(Ti,Ta) phase in acicular Widmanstätten, cellular and rod-like shapes with the addition of Al, Ti, and Ta. Long-term aged CoCrNi MEAs hold same levels (or sometimes slightly weaker levels) of room- and high-temperature strengths as those MEAs under the standard heat treatment. Specifically, CoCrNi MEA with 2%Al, 2%Ti, and 1%Ta presents an ultimate strength of 1012 MPa at room temperature and a yield strength of 695 MPa at 700 °C. Surprisingly, all of the relevant long-term aged MEAs exhibit superior plasticity to that under standard heat treatment. The anomalous mechanical properties are firstly attributed to the γ' phase precipitation. Next, η phase plays an important role in strengthening, improving or at least harmless plasticizing effect since the η phase has the preferential orientation relationship of [011]γ//[2110]η, {111}γ//{0001}η with the γ matrix. It has been confirmed that the strengthening mechanisms are ascribed to the dislocation accumulation and proliferation, formation of stacking faults and nanotwinning in γ, γ' and η phase induced by the precipitation of γ′ and η phase.

Orientation relationships in Cu/Nb bilayers deposited on (001) and (111) NaCl substrate

Cu/Nb bilayers with equal layer thickness of 35 nm were grown on (001) and (111) NaCl substrates using electron beam evaporation at 350 °C. Plan-view Cu/Nb bilayer samples were prepared by dissolving NaCl substrate in water. Transmission electron microscopy (TEM) was performed to study the orientation relationships (ORs). It was found that ORs in Cu/Nb bilayers are dependent on the substrate orientation. For Cu/Nb deposited on (001) NaCl, the dominant OR is Pitsch. For Cu/Nb deposited on (111) NaCl, the dominant OR is Nishiyama-Wasserman (N-W). The preferential ORs found in the Cu/Nb bilayers can be successfully predicted by the invariant line model.

Investigation of the preferred orientation relationships between the in-situ synthesized TiC and titanium matrix

The coplanar reciprocal lattice points (CRLPs) method was used to predict the preferred orientation relationships between α-Ti and TiC. The calculation result shows that two orientation relationships satisfy the criterion, i.e. (0001)α-Ti // (111)TiC, [12¯10]α-Ti // [11¯0]TiC and (101¯0)α-Ti // (111¯)TiC, [0001]α-Ti // [101]TiC. The predicted orientation relationships agree with the published experimental results and present a small lattice misfit on the interface plane. The calculated interface energies indicate that the Ti-terminated rather than C-terminated interface configuration will be formed. The negative interface energies explain the diffusion of the C atom on the interface region. The preferential orientation relationship of (0001)α-Ti//(111)TiC and [12¯10]α-Ti//[11¯0]TiC possesses the lowest interface energy and might be formed in a relatively slow cooling rate process. However, in some rapid cooling processes, the larger undercooling might lead to the formation of (101¯0)α-Ti//(111¯)TiC and [0001]α-Ti//[101]TiC, even if its interface energy is large than the former one. The calculation results indicate that the CRLPs method can provide an effective means to select the potential orientation relationships, on which the first principles calculation can be carried out in a reasonable and acceptable range.

In Situ Tensile Deformation and Mechanical Properties of α Platelets TC21 Alloy.

The present study was focused on the relationship between an α platelet microstructure and the properties of TC21 alloy, and the tensile deformation process was revealed by in situ observation. To obtain the α platelet microstructures, the samples were administered a solution treatment (1000 °C for 15 min) and then cooled to room temperature by different cooling methods (furnace cooling (FC), open-door furnace cooling (OFC), air cooling (AC), and water quench (WQ), corresponding to an increased cooling rate). It is found that α platelets become thinner and colonies become narrower with the increase in cooling rate. The formation of the platelet microstructure is based on the preferred Burgers orientation relationship of {110}β//{0001}α and <111>β//<110>α. The α platelets orientation changes with the cooling rate. These differences in α platelets thickness and orientation result in the excellent ductility of the sample with thick platelets and the high strength of the samples with thin platelets. During the in situ tensile deformation process, the crack propagation path is deflected in the presence of grain boundaries, α platelets, and α colonies with different orientations. The fracture of the sample with thick α platelets shows better ductility compared to those with thin α platelets.

Characterization of the Crystallographic Preferred Orientation Relationships of the Magnetite-Hematite-Goethite Phase Transformation during Martitization

The most frequent crystallographic preferred orientations developed during the progressive phase transformation of magnetite-hematite-goethite are described and analyzed in two natural samples of banded iron formations from Carajás Mineral Province. Microtextures of martitized grains containing the three phases and the microplaty matrix were analyzed in a scanning electron microscope equipped with a detector for electron backscatter diffraction. For identifying the correlation between magnetite, hematite and goethite lattice and topotaxity during transformation, multiple orientation relationships between the three phases were tested and verified using three-dimensional misorientation analysis. The results show that basal planes of goethite coincide with basal planes of hematite, which coincide with octahedral planes of magnetite. This indicates that transformation between the three minerals happens topotactically, and the oxygen lattice framework is preserved in all members of the reaction as a form of crystallographic memory. As a result of progressive and cyclical changes in oxidation/reduction conditions, an assemblage of high-order orientation relationships is observed and assigned to a complex process of transformation twinning in-between phase transformation of magnetite, hematite and goethite. In the N4WS iron ore deposit, iron oxides/hydroxides from martitized grains work as susceptible markers of environmental changes still in solid state during the diagenetic process.

Effects of exsolution on the stability and morphology of Ni nanoparticles on BZY thin films

Yttria doped barium zirconate (BZY) is of interest for use as a catalyst support material, supporting exsolved Ni nanoparticles. Exsolution has been hypothesized to impart catalytic nanoparticles with exceptional resistance to particle coarsening, a known degradation mechanism in catalysts. However, the mechanisms and kinetics of Ni nanoparticle coarsening in BZY are unknown. This work analyzes the kinetics of the coarsening of exsolved Ni nanoparticles on epitaxial BZY thin films at three temperatures (600, 700, and 800 ∘C) over a time span of 150 h. It is demonstrated that Ni coarsening transitions from an Ostwald ripening process to particle migration and coalescence after Ni particles reach a critical size. The coarsening behavior of BZY/Ni is shown to be dependent on the BZY surface orientation, with Ni particles on (111) oriented thin films coarsening the least. The preferred orientation relationships between Ni and BZY on (100), (110), and (111) oriented films are determined. Additionally, the morphology of Ni particles produced through exsolution and thin film dewetting are compared, showing that the socketing behavior and interfacial energy are independent of the Ni particle preparation method.

Mechanism on preferred orientation roof-type Cu6Sn5 grain formation in micro-bump with (111) nanotwinned copper UBM

The (111) nanotwinned copper films used as a novel under bump metallization (UBM) were applied in micro-bump solder technology for 3D packaging. The orientation and morphology of interfacial Cu 6 Sn 5 grains on (111) nanotwinned copper UBMs were investigated by soldering at different temperatures (250 °C and 300 °C). The (11−20) preferred orientation roof-type Cu 6 Sn 5 intermetallic compound (IMC) formed on Sn/(111) nanotwinned copper interface at a higher soldering temperature of 300 °C; while random orientation scallop-type Cu 6 Sn 5 grains formed on Sn/(111) nanotwinned copper interface at lower soldering temperature of 250 °C. The preferred orientation relationships between and interfacial roof-type Cu 6 Sn 5 grains and (111) nanotwinned copper UBMs are {11−20} Cu6Sn5 ||{111} copper in 〈0001〉 Cu6Sn5 ||〈011〉 copper and {11–20} Cu6Sn5 ||{111} copper in 〈10−10〉 Cu6Sn5 ||〈112〉 copper . Moreover, the average shear strength of the (111) nanotwinned copper/Sn/(111) nanotwinned copper solder interconnects soldered at 300 °C (40.19 MPa) is 30% higher than that soldered at 250 °C (31.09 MPa). This study provides an insight in controlling the morphology and orientation of interfacial Cu 6 Sn 5 grains on the (111) nanotwinned copper used as UBMs for the 3D packaging application. • Random intersecting angles of roof-type Cu 6 Sn 5 grains formed on (111) nt-Cu UBM. • ORs: {11–20} η ||{111} Cu in <0001> η ||<011 > Cu , {11–20} η ||{111} Cu in<10–10 > η||<112 > Cu . • Average shear strength of the solder interconnects soldered at 300 °C is 40.19 MPa.

Directionally solidified Al2O3/(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 eutectic high-entropy oxide ceramics with well-oriented structure, high hardness, and low thermal conductivity

Directionally solidified Al2O3/(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 eutectic high-entropy oxide ceramics (HEOCs) were successfully prepared with an optical floating zone furnace. The Al2O3/(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 eutectic HEOCs were pure phases with uniform distribution of rare-earth elements. The preferred growth orientation relationships were <10−10 > {0001}Al2O3 // <110 > {211}(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12. The indentation fracture toughness and Vickers hardness were 6.8 ± 0.9 MPa·m1/2 and 16.1 ± 0.3 GPa, which were higher than that of Al2O3/Y3Al5O12 eutectic ceramics. The room temperature bending strength was 333 ± 42 MPa. Crack bridging, deflection and bifurcation were the main toughening mechanism. Hardness and reduced modulus mapping results illustrated that the hardness of (Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 was close to that of Al2O3. Thermal expansion coefficient of Al2O3/(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 eutectic HEOCs was very similar to that of Al2O3/Y3Al5O12 but thermal conductivity was as low as 4.9 Wm−1 K−1 due to strong lattice distortion. These results suggest that high-entropy Al2O3/(Y0.2Er0.2Yb0.2Ho0.2Lu0.2)3Al5O12 eutectic ceramics are promising candidates for structural components application in gas turbine engines.

Microstructure and mechanical properties of the ZrB2–SiC eutectic phase obtained via induction plasma spheroidization

The microstructure, phase composition and interfaces of ZrB2-30 vol%SiC eutectic were investigated using TEM fabricated via induction plasma spheroidization(IPS). The obtained ZrB2–SiC hypereutectic consists of the alternating H–ZrB2 and 6H–SiC lamellas, and its composition is ZrB2-65.04 mol.%SiC. 3 types of interfaces including SiC lamella-ZrB2 granule, ZrB2 lamella-SiC lamella and ZrB2 lamella-ZrB2 granule present a preferential orientation relationship. High-resolution TEM observations show that the ZrB2 phase in the eutectic prefers to growth along the (101) plane. In addition, the mechanical properties of each phase in the IPS-treated ZrB2–SiC powder were measured by nanoindentation. Hardness and elastic modulus of ZrB2 granules were measured 17.86 GPa and 168.97 GPa, respectively, while these values were obtained 9.99 GPa and 120.66 GPa for ZrB2–SiC eutectic phase.

Gold-rutile interfaces with irrational crystallographic orientations

Gold-rutile interfaces have been extensively investigated particularly because of their importance to heterogeneous catalysts for many reactions such as CO oxidation and water-split reactions. Herein, we systemically study preferential orientation relationships (ORs) and atomic structures at gold-rutile interfaces using a model system of dewetted gold particles on a single-crystal rutile substrate. Four previously reported ORs are confirmed, and more importantly, a few irrational ORs (i.e., which cannot be described by low-indexed planes and directions) are newly discovered. These ORs agree with theoretical possibilities predicted according to the geometrical constraint of adjacent lattices. In addition, atomic rearrangement is observed at these interfaces, particularly in those with irrational ORs.

Microstructural characterization of arc-melted and directionally solidified near-eutectic molybdenum–silicon–boron alloys

Samples of near-eutectic Mo–Si–B alloys, with the nominal composition corresponding to the Moss + Mo3Si + T2 eutectic area, were prepared by arc-melting or by crucible-free zone-melting methods (directional solidification). In the directionally solidified (DSed) alloy, the volume fraction of the Moss + Mo3Si + T2 eutectic cells appeared to increase compared with that of arc-melted (AMed) alloy, and well-aligned and rod-shaped Moss and T2 phases were formed in a Mo3Si matrix of the eutectic cells. In the AMed alloy, only the T2 phase showed a <100] preferential growth orientation along the solidification direction, whereas the Moss phase displayed no obvious preferred orientation. The Mo3Si matrix showed a weak preference toward <001> growth along the solidification direction in the AMed alloy, and this became much stronger in the DSed alloy. Furthermore, the DSed alloy exhibited an apparent preferential growth orientation relationship of <001>Moss//<001>Mo3Si//<100]T2 along the solidification direction. However, no specific atomic structures were observed at the interfaces, indicating that the three phases grew independently from the liquid without the formation of any habit interface during solidification.

Electrochemical Sensing Behaviour of Fabricated Au-SnO2 /ITO Electrode

Functional nanomaterials formed after the combination of a metal oxide and metal play a prominent role in the world of nanotechnology [1]. The interaction between them generates the formation of the interfacial bonds that are mainly responsible for the adhesion strength occurring at the interfaces. Such materials find utilization in numerous fields of electronics, solar cells and chemical sensing [2]. Nanoparticle research presents widespread span for the corroboration of pioneering revelations in the field of medicines, cosmetics, optics and electronics. Astonishing outcomes result from altering the molecular and atomic states of the materials which may not be possible by using them in their original states. Tin dioxide (SnO2) has been colossally used as sensing material in optoelectronic devices, and solid-state gas sensors owing to its stupendous electrical properties escorted by elevated chemical stability [3]. However, very few reports of SnO2 nanoparticles regarding biomolecule detection are available [4]. The sensing characteristics of SnO2 can further be improved by chemical doping with appropriate transition metals such as Pt, Pd, Au, Ag, Ru and Rh [5]. The addition of Au offers suitable platform for the detection of specific analytes [6]. Sol gel method was used to synthesize SnO2 and Au-SnO2 nanoparticles. Structural, morphological and chemical composition of the synthesized nanoparticles was confirmed by XRD, FESEM, TEM, FTIR, and EDS spectroscopic techniques. A frenzy of excitement has generated in electrochemistry by the application of nanotechnology. The electrochemical sensing response of the synthesized nanoparticles was checked after depositing them on ITO substrate. The comparison of the electrochemical performance of Au-SnO2/ITO electrode was done with SnO2/ITO and ITO by cyclic voltammetry (CV), differential pulse voltammetry (DPV) cyclic and electrochemical impedance spectroscopy (EIS). All studies were carried out in phosphate buffer (pH 7.0) at room temperature. The synthesized sensor exhibited good storage stability, specificity and reproducibility with RSD 1.73%. The practical application of the fabricated electrode was demonstrated in real sample with excellent recovery. Reference Wisnios, A. Kiejna, J. Korecki, Towards understanding MgO/Fe interface formation: Adsorption of O and Mg atoms on an Fe(001) surface, Phys. Rev. B 96 (2017) 115418.Nalepka, K. Sztwiertnia, P. Nalepka, Preferred orientation relationships at the Cu/α−Al2O3interface: Identification and theoretical explanation, Acta Mater. 104 (2016) 156–165.Tournier, C. Pijolat, Influence of oxygen concentration in the carrier gas on the response of tin dioxide sensor under hydrogen and methane, Sens Actuators B 61(1999) 43-50.Lavanya, S. Radhakrishnan, C. Sekar, Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles, Biosen. Bioelectron, 36 (2012) 41-47.Cheraghi, M. A. Taher, H. Karimi-Maleh, R. Moradi, Simultaneous detection of nalbuphine and diclofenac as important analgesic drugs in biological and pharmaceutical samples using a Pt: Co nanostructure-based electrochemical sensor, J Electrochem Soc. 164 (2017) B60-B65.Zhang, X. Liu, S.Wu,M. Xu, X. Guo, S. Wang, Au nanoparticle-decorated porous SnO2 hollow spheres: a new model for a chemical sensor J. Mater. Chem. 20(2010) 6453–9.

Influence of step structure on preferred orientation relationships of Ag deposited on Ni(111)

Previous studies have shown that the orientation relationships which develop in hetero-epitaxy are strongly influenced by the alignment of steps in the deposit with the pre-existing steps of the substrate. In this paper we use a combination of experiments with computer simulations to identify the important influence of substrate step structure on the eventual orientation relationships that develop in the deposit. We have made use of Ag deposited on Ni as it has been used extensively as a model system for the study of hetero-epitaxy. This system displays a large lattice mismatch of 16%. It is shown that on any surface vicinal to Ni(111), which has two possible kinds of 〈110〉 steps (A-steps with {100} ledges and B-steps with {111} ledges), a Ag deposit adopts a single orientation relationship because only A-steps remain stable in the presence of Ag.

On surface carbides in low-temperature carburized austenitic stainless steels

Surface carbides are occasionally found at the surface of austenitic stainless steels subjected to low-temperature carburizing surface treatments which are intended to induce an interstitially supersaturated surface layer. The crystallographic nature and chemical composition of the carbides can have a significant influence on the surface properties, especially on the corrosion resistance of the steel. However, their phase identification and chemical characterization via conventional methods (e.g. X-ray diffraction) is difficult due to their complex structure and metastable nature. In this paper, a combined metallographic and electron microscopic approach is applied to characterize the morphology and chemical composition of surface carbides found on AISI 304L and SS2343 after the same Kolsterising® treatment. Exclusively M5C2, also known as Hägg or χ-carbide was found at the surface of 304L, preferentially oriented along (111) deformation bands. In SS2343, however, χ-carbide coexisted with M7C3 (or ω-carbides) and M23C6. The carbides had preferential orientation relationships with the matrix, suggesting a carbide evolution during carburizing. All the carbides show elemental partitioning, with Cr enrichment and Ni depletion. A microstructure development sequence regarding precipitation and growth of surface carbides is proposed in this paper.