Subjects -> METALLURGY (Total: 59 journals)
 Showing 1 - 10 of 10 Journals sorted alphabetically Acta Metallurgica Slovaca       (Followers: 2) Advanced Device Materials       (Followers: 6) American Journal of Fluid Dynamics       (Followers: 44) Archives of Metallurgy and Materials       (Followers: 9) Asian Journal of Materials Science       (Followers: 4) Canadian Metallurgical Quarterly       (Followers: 21) Complex Metals       (Followers: 2) Energy Materials : Materials Science and Engineering for Energy Systems       (Followers: 24) Graphene and 2D Materials       (Followers: 6) Handbook of Ferromagnetic Materials       (Followers: 1) Handbook of Magnetic Materials       (Followers: 2) High Temperature Materials and Processes       (Followers: 6) Indian Journal of Engineering and Materials Sciences (IJEMS)       (Followers: 11) International Journal of Metallurgy and Alloys       (Followers: 2) International Journal of Metals       (Followers: 7) International Journal of Minerals, Metallurgy, and Materials       (Followers: 12) International Journal of Mining and Geo-Engineering       (Followers: 4) Ironmaking & Steelmaking       (Followers: 5) ISIJ International - Iron and Steel Institute of Japan       (Followers: 26) Izvestiya Vuzov. Poroshkovaya Metallurgiya i Funktsional’nye Pokrytiya (Proceedings of Higher Schools. Powder Metallurgy аnd Functional Coatings)       (Followers: 2) JOM Journal of the Minerals, Metals and Materials Society       (Followers: 35) Journal of Advanced Joining Processes Journal of Central South University       (Followers: 1) Journal of Cluster Science Journal of Heavy Metal Toxicity and Diseases Journal of Iron and Steel Research International       (Followers: 11) Journal of Materials & Metallurgical Engineering       (Followers: 2) Journal of Materials Processing Technology       (Followers: 21) Journal of Metallurgical Engineering       (Followers: 4) Journal of Sustainable Metallurgy       (Followers: 3) Materials Science and Metallurgy Engineering       (Followers: 7) Metal Finishing       (Followers: 20) Metallurgical and Materials Engineering       (Followers: 7) Metallurgical and Materials Transactions A       (Followers: 42) Metallurgical and Materials Transactions B       (Followers: 32) Metallurgical and Materials Transactions E       (Followers: 2) Metallurgical Research & Technology Metallurgical Research and Technology       (Followers: 8) Metallurgy and Foundry Engineering       (Followers: 3) Mining, Metallurgy & Exploration Powder Diffraction       (Followers: 1) Powder Metallurgy       (Followers: 35) Powder Metallurgy and Metal Ceramics       (Followers: 7) Powder Metallurgy Progress       (Followers: 5) Practical Metallography       (Followers: 6) Rare Metals       (Followers: 3) Revista de Metalurgia Revista del Instituto de Investigación de la Facultad de Ingeniería Geológica, Minera, Metalurgica y Geográfica Revista Remetallica       (Followers: 1) Russian Metallurgy (Metally)       (Followers: 4) Science and Technology of Welding and Joining       (Followers: 8) Soldering & Surface Mount Technology       (Followers: 2) Steel Times lnternational       (Followers: 19) Transactions of the IMF       (Followers: 14) Transactions of the Indian Institute of Metals       (Followers: 5) Tungsten Universal Journal of Materials Science       (Followers: 3) Welding in the World       (Followers: 8) Welding International       (Followers: 11) Вісник Приазовського Державного Технічного Університету. Серія: Технічні науки
Similar Journals
 Metallurgical and Materials Transactions AJournal Prestige (SJR): 1.093 Citation Impact (citeScore): 2Number of Followers: 42      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1543-1940 - ISSN (Online) 1073-5623 Published by Springer-Verlag  [2655 journals]
• Combined Effect of Sodium Lauryl Sulphate and Saccharin on Microstructure
and Corrosion Performance of Electrodeposited Nickel Prepared from
Modified Watts Bath
• Abstract: Additives in Watts bath influence the surface properties of the electrodeposited nanocrystalline nickel. The changes in the properties are led by the alteration in the nucleation and plating over-potentials ( $$E_{n}$$ & $$E_{p}$$ ). A galvanodynamic polarization technique was used to determine the $$E_{n}$$ & $$E_{p}$$ in the modified Watts bath. From all the commercially available additives, sodium lauryl sulfate (SLS) was used as an anti-pitting agent, and saccharin (SAC) was added as a grain refiner. The concentration of SAC was varied in the range from 1.5 to 10 $${\text{ml}}/{\text{l}}$$ while keeping SLS concentration constant at 1.1 $${\text{g}}/{\text{l}}$$ in order to see its effect on polarization potentials, surface roughness, and corrosion behavior. Refinement of surface roughness and crystallite size, corresponding to steady values of $$E_{n}$$ & $$E_{p}$$ was obtained for SAC at 3 ml/l and SLS at 1.1 g/l. The deposits with fine crystallite size showed minimal passivation current density and highest polarization resistance.
PubDate: 2021-03-13

• Role of Microstructure and Temperature on the Tensile Fracture Behavior of
Oxide Dispersion Strengthened 18Cr Ferritic Steel
• Abstract: The tensile fracture behavior of oxide dispersion strengthened 18Cr (ODS-18Cr) ferritic steels milled for varying times was studied along with the oxide-free 18Cr steel (NODS) at 25, 200, 400, 600, and 800 °C. At all the test temperatures, the strengths of ODS–18Cr steels increased and total elongation decreased with the duration of milling time. Oxide dispersed 18Cr steel with optimum milling exhibited enhanced yield strength of 156 pct at room temperature and 300 pct at 800 °C when compared to oxide-free 18Cr steel. The ductility values of ODS-18Cr steels are in the range 20 to 35 pct for a temperature range 25 to 800 °C, whereas NODS alloy exhibited higher ductility of 37 to 82 pct. The enhanced strength of ODS steels when compared to oxide-free steel is due to the development of ultrafine grained structure along with nanosized dispersion of complex oxide particles. While the pre-necking elongation decreased with increasing temperature and milling time, post-necking elongation showed no change with the test temperature. Fractographic examination of both ODS and NODS 18Cr steel fractured tensile samples, revealed that the failure was in ductile fracture mode with distinct neck and shear lip formation for all milling times and at all test temperatures. The fracture mechanism is in general followed the sequence; microvoid nucleation at second phase particles, void growth and coalescence. The quantified dimple sizes and numbers per unit area were found to be in linear relation with the size and number density of dispersoids. It is clearly evident that even nanosized dispersoids acted as sites for microvoid nucleation at larger strains and assisted in dimple rupture.
PubDate: 2021-03-13

• Evaluation of Thermal and Mechanical Behavior of CuNiCoZnAl High-Entropy
Alloy Fabricated Using Mechanical Alloying and Spark Plasma Sintering
• Abstract: Thermal behavior investigation of CuNiCoZnAl high-entropy alloy powder produced by mechanical alloying indicated that a FCC single-phase solid solution transformed into two new phases at 500 °C. Despite this phase transformation, no indication of intermetallic compounds or amorphous phases was detected. Heat treatment of the high-entropy alloy was then carried out for 2 hours, and the nanocrystalline structure of heat-treated milled powder was retained up to 1000 °C. Besides, grain growth of CuNiCoZnAl high-entropy alloy powder at high homologous temperatures (> 0.6 Tm) was studied, and sluggish grain growth of the powder was observed clearly. Consolidation of the alloy powder was performed by spark plasma sintering at 800 °C, and a sample with porosity of 6.87 pct and density of 7.32 g cm−3 was achieved. Elastic moduli, Vickers microhardness, and fracture toughness of the bulk sample were measured as 186 ± 17 GPa, 599 ± 31 HV, and 4.45 MPa m0.5, respectively. The evaluation of wear behavior indicated that the dominant wear mechanism was adhesive wear. Moreover, tribochemical wear (oxidation) was found to be the minor wear mechanism. The present study revealed that CuNiCoZnAl high-entropy alloy has the potential to be used in many applications that high hardness and low elastic moduli are favorable.
PubDate: 2021-03-13

• Microstructure-Based FEM Modeling of Phase Transformation During Quenching
of Large-Size Steel Forgings
• Abstract: The current investigation encompasses the development of a microstructure-based 3D finite element model (FEM) of water quenching process of large-size, high-strength steel forgings with accurate predictions of the volume fraction of phases. The approach is based on modified TTT/CCT curves that consider a lower martensite start temperature value. An experimental procedure consisting in the validation of the FEM simulations was conducted using high-resolution dilatometry, optical and scanning electron microscopy, and instrumentation of a large-size steel block with several thermocouples at different locations. Results showed a very good agreement between the temperature predictions of the 3D FEM model and those obtained from direct measurement of instrumented forged block with an average error of about 1 pct in the quarter region. The volume fraction of phases and hardness distribution across the block were also predicted by the proposed 3D FEM model. The numerical results revealed bainitic volume fractions of about 74 pct at the center of the block and about 91 pct in the quarter region. These predictions were also confirmed by dilatometry test and metallographic examination of the microstructure. Micro hardness measurements were conducted on dilatometry samples that simulate the heat treatment cycle of different thicknesses of the forged block were compared with those predicted by the FEM, and very good agreements were obtained, further confirming the validity of the simulations. The proposed procedure in this research improves the quality of predictions by increasing the reliability of material parameters such as TTT optimization and accurate determination of thermo-physical parameters.
PubDate: 2021-03-12

• Effects of Pore Geometry on the Fatigue Properties of Electron Beam Melted
Titanium-6Al-4V
• Abstract: Current percent-porosity based quantification of pores in additively manufactured parts does not provide information about the size, shape, and distribution of pores throughout a build. Such information is necessary to understand the conditions under which the part was printed as well as its mechanical reliability. This research, through a combination of fatigue testing and microstructural characterization demonstrates a method by which the internal porosity can be characterized and using the knowledge of the pores differing formation mechanisms to inform future design and build strategies. Though the test bars were printed under nominally identical conditions, ignoring lack-of-fusion, batch 1 had 34 pct fewer lenticular pores and 147 pct more spherical pores than batch 2 which shows that the actual print conditions of these parts varied substantially as would their as-printed mechanical reliability. To quantify this difference extensive optical, SEM, and EBSD metallographic studies were conducted on several samples from these bars as well as the fracture surfaces to gain an understanding of the porosity’s shape, size, and location. The comparison of these datasets along with knowledge of the pore’s evolution allows for the optimization of future build strategies and the more accurate prediction of the resulting as-built mechanical properties.
PubDate: 2021-03-12

• Influence of Specimen Layout on 17-4PH (AISI 630) Alloys Fabricated by
• Abstract: This work examined the effects of specimen layout on physical, microstructural, and mechanical properties of 17-4PH (AISI 630) fabricated by metal-fused deposition modeling process. Tensile specimens were 3D-printed with the different layouts using 100 pct infill. The as-printed and as-sintered specimens with the flat layout had the best appearance, green, relative sintered density, and sintered tensile properties with good repeatability, while the specimens with the vertical layout were the worst. The as-sintered tensile properties of specimens with the side layout were slightly lower than those with the flat layout but significantly higher than those with the vertical layout. Moreover, the tensile properties of specimens with the flat and side layouts met the Metal Powder Industry Federation standard 35 for metal injection molding. The tensile properties and corresponding fracture surfaces can be explained in terms of the combined effect of load-bearing and stress concentration due to the pre-existence of voids at perimeters. The fracture surfaces of specimens with the vertical layout showed large defects induced during printing and voids between perimeter walls generating high stress concentration and layer delamination. The difference between tensile properties of specimens with the side and flat layouts is mainly due to the characteristic of the printing—voids in the side layout are larger and more detrimental to the mechanical properties—which was confirmed by the evidence of cracking in the fracture surface.
PubDate: 2021-03-12

• Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd Bulk Metallic Glasses with Potential for
Biomedical Applications
• Abstract: Ti47Cu38−xZr7.5Fe2.5Sn2Si1Ag2Pdx (x = 1, 2, 3, and 4 atomic percent, at. pct) bulk metallic glasses (BMGs) with potential for biomedical applications were fabricated by copper-mold casting. The Ti-based BMGs exhibited high glass-forming ability (GFA) with critical diameters of 4 to 5 mm and a supercooled liquid region over 50 K, though the high contents of Pd slightly decreased the GFA. The additions of 2 and 3 at. pct Pd benefited the improvement of plasticity, and the resultant BMGs showed the relatively low Young’s modulus of about 100 GPa, high compressive strengths of 2174 to 2340 MPa, and compressive plastic strain of around 4 pct. The addition of Pd also decreased the passive current density and increased the pitting potential of the Ti-based BMGs in the Hank’s solution, leading to the enhanced bio-corrosion resistance of the BMGs. Furthermore, the cell adhesion, viability, and proliferation behaviors revealed that the present Ti-based BMGs possess as good biocompatibility as that of the Ti-6Al-4V alloy. These results demonstrated the potential of the Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd BMGs as biomedical materials.
PubDate: 2021-03-12

• Microstructure and Magnetic Properties of 6.5 Wt Pct Si Steel Strip
Produced by Simulated Strip Casting Process
• Abstract: An improved dip test apparatus was used to simulate the strip casting of 6.5 wt pct Si steel in this study. The results showed that the interfacial heat flux between melt and substrate could reach maximum value of 8.2 MW/m2, with > 4350 kJ/m2 heat being removed in the first 1.0 s. The as-cast strip mainly consisted of large columnar grains hundreds of microns in length. The high cooling rate of the as-cast strip suppressed the formation of ordered phases and the precipitation of elements. Only several complex particles of MnS-TiN of a few nanometers were found. After annealing at 1273 K (1000 °C) for 30 minutes, a large number of small particles such as TiN precipitated from the ferrite matrix. Within the testing frequency and magnetic field strength, the three strip samples obtained at different conditions showed the lowest iron loss at the frequency of 20 kHz and the magnetic field strength of 0.07 T, which were 22, 18 and 17 W/kg, respectively. The coercive force and iron loss decreased with increasing heat treatment temperature, while the magnetic permeability showed the opposite pattern. The magnetic permeability and iron loss of the silicon steel strip produced by strip casting are comparable to those of the silicon steel products produced by other techniques such as melt spinning and conventional rolling.
PubDate: 2021-03-12

• Atomistic Simulation on the Mechanical Properties of Diffusion Bonded
Zr-Cu Metallic Glasses with Oxidized Interfaces
• Abstract: A novel welding technique of diffusion bonding for Zr-Cu metallic glass with pre-oxidized surfaces is proposed in this study, which is systematically investigated by molecular dynamics (MD) simulation. Compared with the conventional welding technique, the diffusion bonding process can be well implemented below the crystallization temperature of metallic glass. The obtained structure possesses glass–glass interfaces (GGIs) similar with those in nano-glasses. As revealed by MD simulation, the diffusion bonded metallic glasses possess enhanced mechanical strength and ductility that generally do not exist in nano-glasses and their bulk metallic glass counterparts. The GGIs are found to hinder the propagation of shear bands, where there is strong bonding between Zr and O and the segregated Cu and ZrO2 clusters could induce extra plasticity. The results demonstrate that the diffusion bonding of metallic glass with pre-oxidized surfaces could provide an alternative approach in solving the longstanding issue of size limitation on metallic glasses.
PubDate: 2021-03-11

• Strengthening Mechanisms in Nano Oxide Dispersion-Strengthened Fe-18Cr
Ferritic Steel at Different Temperatures
• Abstract: The objective of the present work is to evaluate isothermal uniaxial compressive deformation behavior of nano oxide dispersion-strengthened (n-ODS)-18Cr ferritic steel over a range of temperatures RT—1173 K and range of strain rates 10−4 to 10−2 s−1. Irrespective of temperature, the influence of the strain rate on the yield strength is insignificant up to 673 K. It is found that the plot of variation of yield strength as a function of temperature exhibits three regimes, which indicates that different deformation mechanisms are governing the yield strength of n-ODS-18Cr steel. Transmission electron microscopic analysis of a sample deformed at the highest temperature of 1173 K and the lowest strain rate of 10−4 s−1 demonstrates no significant change in the grain size and nanoprecipitate size. Also, it confirms the interaction between dislocations and nanoprecipitates. Different deformation mechanisms governing the yield strength of n-ODS-18Cr steel are identified in all three regimes and their contributions are quantified.
PubDate: 2021-03-11

• Inductively Coupled Plasma Process for Reconditioning Ti and Ni Alloy
• Abstract: In laser powder bed fusion additive manufacturing (AM), the number of build cycles required for a powder to go from its virgin state to a state that can alter final part mechanical properties is currently unknown. While ideal, the use of virgin powder for every AM build is not practical or economical. It is critical to investigate new methods that will help mitigate these cost drivers and enable the use of recycled powder in AM. Presented here is initial work on the use of an inductively coupled plasma (ICP) process to recondition AM powders used in laser and electron beam powder bed fusion, highlighting some challenges faced while developing optimum process parameters. The manuscript focuses on the three-dimensional characterization of used powder, before and after the plasma reconditioning process, in order to quantitatively understand the result of the ICP process on the shape and porosity of the particles. A distinct change in the morphology of the powder was observed before and after the ICP where most, but not all, irregular shaped powder particles and multi-particles were converted into more spherical particles. A detailed analysis of the percentage of spherical and non-spherical particles before and after the ICP process is also included, as well as the process’ effect on particle porosity, which was different for the two powders used, Inconel 718 and Ti-6Al-4V. The results indicate the value of using the ICP process as a viable option for recycling of these two powders.
PubDate: 2021-03-11

• The Influence of 3 d and 4 d Transition Metals on the Glass Forming
Ability of Ternary FeCo-Based Alloys
• Abstract: Thermodynamic modeling was used to determine enthalpies of formation and other thermodynamic parameters describing glass forming ability of Fe-Co-TM (TM = V, Nb, Cr, Mo) alloys. FeCo-based alloys are considered as candidates for applications as high magnetic flux density materials due to their high magnetic saturation and low magnetic anisotropy. Nevertheless, mechanical properties, especially the lack of ductility, are their main weakness. Therefore, further optimization by vitrification, further heat treatment and alloying should be considered. As the most crucial step is the synthesis of amorphous precursors, discussion is concentrated on the effect of transition metal substitution on the glass forming ability. The highest glass forming ability was reported for Fe-Co-Nb alloys. It can be also noted that the driving force for vitrification can be improved by substitution of Fe by other transition elements, as glass forming ability parameter ∆PHS reaches the lowest values for Fe-less compositions.
PubDate: 2021-03-11

• Effects of Microstructure and Material Composition on the Formation
Kinetics of Passive Film and Pitting Behavior of Super 13Cr Stainless
Steel
• Abstract: The effects of the microstructure and material composition on the formation kinetics of passive film and pitting behavior of super 13Cr stainless steel (S13Cr SS) were investigated and compared with those of 2Cr13 stainless steel (2Cr13 SS). The results indicated that the passive film formed on S13Cr SS surface quickly reached a stable state, which was attributed to two reasons. The small grain size coupled with the high dislocations density increased the number of nucleation sites for passive film formation, and the high material composition enhanced the Cr and Mo compound contents in the passive film. The passive film on S13Cr SS was more compact and thicker than that on 2Cr13 SS. The pit depth on S13Cr SS was relatively shallow after potentiodynamic polarization. Therefore, the protective properties of the passive film on S13Cr SS increased, and the pitting corrosion resistance of S13Cr SS was enhanced.
PubDate: 2021-03-10

• In-Situ High-Energy X-ray Diffraction Study of Austenite Decomposition
During Rapid Cooling and Isothermal Holding in Two HSLA Steels
• Abstract: In-situ high-energy X-ray diffraction experiments with high temporal resolution during rapid cooling (280 °C s−1) and isothermal heat treatments (at 450 °C, 500 °C, and 550 °C for 30 minutes) were performed to study austenite decomposition in two commercial high-strength low-alloy steels. The rapid phase transformations occurring in these types of steels are investigated for the first time in-situ, aiding a detailed analysis of the austenite decomposition kinetics. For the low hardenability steel with main composition Fe-0.08C-1.7Mn-0.403Si-0.303Cr in weight percent, austenite decomposition to polygonal ferrite and bainite occurs already during the initial cooling. However, for the high hardenability steel with main composition Fe-0.08C-1.79Mn-0.182Si-0.757Cr-0.094Mo in weight percent, the austenite decomposition kinetics is retarded, chiefly by the Mo addition, and therefore mainly bainitic transformation occurs during isothermal holding; the bainitic transformation rate at the isothermal holding is clearly enhanced by lowered temperature from 550 °C to 500 °C and 450 °C. During prolonged isothermal holding, carbide formation leads to decreased austenite carbon content and promotes continued bainitic ferrite formation. Moreover, at prolonged isothermal holding at higher temperatures some degenerate pearlite form.
PubDate: 2021-03-10

• Local Composition Migration Induced Microstructural Evolution and
Mechanical Properties of Non-equiatomic Fe 40 Cr 25 Ni 15 Al 15 Co 5
Medium-Entropy Alloy
• Abstract: A newly designed composition of non-equiatomic Fe40Cr25Ni15Al15Co5 medium-entropy alloy (MEA) was produced by induction melting (IM). The as-cast alloy was found to consist of a two-phase microstructure of BCC (2.87 ± 0.01 Å) and ordered B2 (2.88 ± 0.02 Å) type phases. The structures of these phases were confirmed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It was observed that the Ni-Al-enriched ordered B2 phase of cuboidal shapes (~ 100 to 200 nm) is homogeneously distributed in Fe-Cr-rich BCC matrix with a cube-on-cube orientation relationship. The formation of the columnar dendrites (width 50 to 100 μm) was identified through optical microscopy (OM). The structural and microstructural stability of the alloy was investigated by heat-treating the alloy through different schedules. Heat-treated samples at different temperatures (< 1273 K) exhibit a similar type of two-phase microstructure with columnar dendrites. However, compositional rearrangement takes place during long time exposure to develop polymorphically related phases. The alloy was observed to possess a high compressive yield strength and hardness, i.e., ~ 1047 MPa and 391 ± 9 HV, respectively, at room temperature. Heat-treated samples at 600 °C and 900 °C (873 K and 1173 K) showed an increase in yield strength and ultimate strength with a significant increase in plasticity due to the increase in volume fraction of B2 phase and softening of the BCC matrix phase. The thermal stability and high strength of this alloy may open new avenues for high-temperature applications.
PubDate: 2021-03-10

• Evolution of Microstructure and Mechanical Properties of As-Cast Al x CrFe
2 Ni 2 High-Entropy Alloys with Al Content
• Abstract: This study designed a series of low-cost AlxCrFe2Ni2 high-entropy alloys with different Al contents (x = 0.1-1.0 at.) and investigated their microstructure and mechanical properties. The XRD analysis revealed that, with an increase in the Al content, their crystalline structures changed from the initial single face-centered cubic (FCC) one to FCC plus body-centered cubic (BCC) and ordered BCC (B2) structures. The tensile strength and hardness first increased and then dropped with increasing Al content related to the volume fraction of the FCC/BCC phase. At x = 0.9, the as-cast alloy containing 49.1 pct BCC phase exhibited the highest ultimate tensile strength of 1278 MPa with a 12.6 pct ductility. With an increase in the Al content, the alloy fracture mechanism changed from ductile fracture to brittle.
PubDate: 2021-03-10

• Developing a M 6 C-Reinforced High-Cr White Iron for Abrasive Wear
Application
• Abstract: Fast removal of soft phases (e.g., pearlite and ferrite) in the iron matrix limits the wear life of high-Cr white irons. To address this shortcoming, the authors successfully produced fine networks of M6C carbide in a high-Cr white iron through extensive thermodynamic calculations. Fishbone-like networks of M6C carbides were observed with an optical microscope. It was experimentally determined that such carbide networks protected the soft matrix and increased the overall hardness. Additionally, electron backscattered diffraction was conducted, which showed that the alloy contained phases of M7C3, M6C, ferrite, and retained austenite. Solidification sequence was determined by correlating the thermodynamic equilibrium calculation results with the size and distribution of each phase. A dry sand/rubber wheel apparatus following ASTM standard G65 Procedure A was utilized to assess the abrasive wear performance of the developed alloy. Results showed that the volume loss of the developed material was 25 pct less than that of conventional high-Cr white irons. Wear scars were investigated using a scanning electron microscope, and the improved wear resistance was attributed to the “buffer” effect and plastic deformation of the introduced M6C carbide networks.
PubDate: 2021-03-10

• The Effect of β Stabilizers on the Structure and Energy of α / β
Interfaces in Titanium Alloys
• Abstract: The structure and energy associated with interfaces between the BCC and HCP lattices (β and α phase, respectively) in titanium alloys with commonly used β stabilizers were analyzed. For this purpose, the crystallographic structure of the matching facets of broad, side and end faces was described using misfit dislocations and structural ledges which compensate the mismatch in atomic spacing of the α and β phases. The effect of the β/α transformation temperature due to various concentration of β stabilizers on periodicity of misfit dislocations and structural ledges was estimated. The van der Merwe approach was used to calculate energy of different matching facets. An increase in the percentage of β-stabilizing elements was found to result in a decrease in the lattice-parameter ratio (aβ/aα) and an increase in the energy of all faces. The dependence of the interface energy on the aβ/aα ratio was for the first time quantified, and insight into the preferred shape of α-phase precipitates was obtained.
PubDate: 2021-03-09

• Mechanistic Modeling of Cyclic Softening and Slip Localization in Ni-Based
Superalloys
• Abstract: Ni-based superalloys are typically strengthened with ordered fcc $$\gamma^{\prime}$$ precipitates (L12 structure) which impart a number of hardening mechanisms including anomalous hardening due to cross slip from {111} to {010} planes. On the other hand, the presence of shearable $$\gamma^{\prime}$$ precipitates promotes cyclic softening and slip localization. The onset of cyclic softening and slip localization processes in $$\gamma^{\prime}$$ -strengthened Ni-based superalloys is still poorly understood and has not been modeled. In this investigation, the salient mechanisms responsible for cyclic softening and slip localization in Ni-alloys containing $$\gamma^{\prime}$$ precipitates are reviewed and the pertinent information is utilized to develop mechanistic models for predicting the cyclic response, slip localization, and fatigue life of this class of engineering alloys. Mechanistic modeling reveals that cyclic softening and slip localization can be attributed to three processes: (1) stable expansion of superkinks with subcritical kink heights, (2) shearing, and (3) bowing of $$\gamma^{\prime}$$ precipitates. The onset of cyclic softening commences in the microplastic regime and occurs when the accumulated shear strain along the operative {111} plane exceeds the average $$\gamma^{\prime}$$ size. The roles of cyclic softening and slip localization in reducing high-cycle fatigue strength and fatigue life are elucidated and discussed.
PubDate: 2021-03-09

• Cluster Variation Method Analysis of Correlations and Entropy in BCC Solid
Solutions
• Abstract: Solid solutions occur when multiple chemical species share sites of a common crystal lattice. Although the single site occupation is random, chemical interaction preferences bias the occupation probabilities of neighboring sites, and this bias reduced the entropy of mixing below its ideal value. Sufficiently strong bias leads to symmetry-breaking phase transitions. We apply the cluster variation method to explore solid solutions on body centered cubic lattices in the context of two specific compounds that exhibit opposite ordering trends. Employing density functional theory to model the energetics, we show that CuZn exhibits an order-disorder transition to the CsCl prototype structure, while AlLi instead takes the NaTl prototype structure, and we evaluate their temperature-dependent order parameters, correlations and entropies.
PubDate: 2021-03-08

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