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We study the phenomenon of strain hardening of 1565ch and AMg6 aluminum alloys of the Al – Mg system with high magnesium contents and 01570 and 1580 alloys with additions of scandium in the process of cold rolling of plates. We plot hardening curves approximated by the well-known empirical expressions in the form of power functions constructed with an accuracy sufficient for the engineering calculations of the characteristics of strength within the range of total relative compressions 0 – 35%. It was shown that, in the alloys alloyed with scandium, the phenomenon of hardening observed in the course of cold rolling is weaker than in alloys without scandium. [ABSTRACT FROM AUTHOR]

Cu-Be alloys exhibit excellent comprehensive performance in electrics, thermotics, and mechanics, and hence, they attract much attention. Among them, low-Be copper alloys are more environmentally friendly and promising. This study explores the effects of different Ni contents and heat treatment parameters on the properties, microstructures, and precipitates of Cu-0.2 wt% Be-x wt% Ni (0 < x < 2.0) alloys. The experimental results demonstrate that the fast cooling rate of cast alloys during solidification contributes to retention of the solute atoms in the copper matrix, which is beneficial for subsequent solid solution treatment. Furthermore, solid solution treatment slightly reduces the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The optimal solution temperature and time are about 925 ℃ and 60 min, respectively. Aging treatment significantly increases the electrical conductivities, microhardness values, and compressive yield strengths of Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The best aging temperature is around 450 ℃. However, the properties of Cu-0.2 wt%Be-0.4 wt%Ni alloys remain unaffected by solution and aging treatments. Around x = 1.0, Cu-0.2 wt% Be-x wt% Ni alloys possess the best comprehensive properties, which are about 72%IACS of electrical conductivity, 241 HV of microhardness, and 281MPa of compressive yield strength, respectively. TEM and EDS analyses reveal that the precipitate evolution of Cu-0.2 wt% Be-1.0 wt% Ni alloys with aging time is GP zones → γ″ → γ′. Notably, a distinct double-peak age strengthening phenomenon emerges with Cu-0.2 wt% Be-1.0/1.6 wt% Ni alloys. The precipitation of plenty of GP zones at the early stage of aging should account for the first strengthening peak, and the strengthening mechanism transformation of the γ″ or γ′ phase from shear to Orowan should induce the second strengthening peak. This work may help to design new low-Be copper alloys and their preparation processes. [ABSTRACT FROM AUTHOR]

Aluminum matrix nanocomposites (AMNCs) are a distinct category of advanced materials that incorporate nanoscale reinforcement in a ductile material matrix. Various nanomaterial reinforcements for AMNCs have been reported in the literature, including multi-walled carbon nanotubes (MWCNT), graphene nanoplatelets, silicon carbide, and boron nitride. These classes of materials have been described to exhibit both improvements and reductions in mechanical properties. The interfacial material phases result in low-strength materials. Improvements in mechanical properties are attributed by refined grain size and shape for both the matrix material and the reinforcement agent. These materials demonstrate higher hardness, yield strength, and wear corrosion compared to conventionally prepared aluminum composites. Spark plasma sintering (SPS) is one of the non-conventional sintering methods used to prepare metal matrix composites, resulting in fully dense composite materials. The SPS-produced metal matrix composite can be manufactured rapidly and finds its applications in the automotive, aerospace, and defense industries. This review provides an overview and current status of metal matrix composites regarding matrix and reinforcing materials and the SPS process for producing metal matrix composites. [ABSTRACT FROM AUTHOR]

Many of the hard tissue implants are made of titanium alloys, due to its low specific strength and low elastic modulus with excellent biocompatibility and good corrosion resistance. The difference in elastic modulus between cortical bone and titanium alloy leads to stress shielding which leads to bone fracture. To avoid this, there is a need of reduction in elastic modulus of available titanium alloy implant with an adequate strength to withstand the applied load. Here three different machine learning techniques, viz. multiple linear regression analysis, artificial neural network and fuzzy inference systems, are employed for designing titanium alloy for biomedical application having lower modulus with adequate strength. The purpose of the work is to find the role of alloying elements and processing parameters in determining the two mechanical properties, so that the alloy can be properly designed to achieve the targeted performance. There were discrepancies between the results generated by different tools. But it was found that alloying elements like Al, Zr, Fe, Sn and Cr play the most significant role in reducing the modulus of elasticity without much compromise in the strength of titanium alloy. [ABSTRACT FROM AUTHOR]

The present paper is aimed to experimentally investigate the influence of a plastic deformation on both yield strength and torsional fatigue life of a CuZn40Pb2 leaded brass alloy and a 6082‐T6 aluminum alloy. Two types of preloading are considered, that is, (i) a cyclic torsion (cyclic preloading) and (ii) a monotonically increasing tension (static preloading). More precisely, for each of the above alloys, different both numbers of loading cycles and maximum values of the static preloading are considered. Moreover, an in‐depth fracture surface analysis on the failed specimens is performed, and fracture mechanisms at different scale lengths summarized. Highlights: Investigation on plastic deformation effect on yield strength of non‐ferrous alloys.Investigation on plastic deformation effect on torsional fatigue life of non‐ferrous alloys.A CuZn40Pb2 leaded brass alloy and a 6082‐T6 aluminum alloy are examinedFracture surface analysis on the failed specimens is performed. [ABSTRACT FROM AUTHOR]

Currently, the interest in the application of metal additive manufacturing (AM), also known as 3D printing, is grown massively in the various fields of the industry and surgery. AM has significant multiple advantages compared to traditional subtractive technologies for making highly customized parts with complex geometries without causing noteworthy extra costs. Now, several powder-based AM technologies for metals’ 3D printing are in progress, in particular, selective laser sintering (SLS), selective laser melting (SLM), and electron-beam melting (EBM). In the past few decades, increasing research and developments are devoted to the wire-feeding-based 3D printing production of parts made of the Ti–6Al–4V alloy, which is widely investigated in different fields such as aerospace, automotive, energy, and marine industries as well as the prosthetics and the production of orthopaedic implants. Due to the feasibility of economical producing large-scale metal components with relatively high deposition rate, low machinery cost, high material efficiency, and shortened lead-time compared to powder-based AM, wire-feeding-based AM (WFAM) is attracting significant attention in the industry and academia owing to its ability for the production of the large components of the medium geometric complexity. In recent years, three options of WFAM are intensively researched, which differ by the wire-melting heating sources: wire + arc additive manufacturing (WAAM); wire-laser AM (WLAM), and wire electron-beam additive manufacturing (WEBAM). The purpose of the present review is systematic analysis of the mechanical properties of the Ti–6Al–4V alloy samples 3D-printed by WFAM with various heating melting sources, namely, arc, laser, and electron beam. Particularly, considering the literature data for the period of 2013–2020, such important properties as yield strength, tensile strength, elongation, and hardness are analysed for the samples in the as-printed and post-processed conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] The pursuit of novel alloys tailored to specific requirements poses significant challenges for researchers in the field. This underscores the importance of developing predictive techniques for essential physical properties of alloys based on their chemical composition and processing parameters. This study introduces AlloyBERT, a transformer encoder-based model designed to predict properties such as elastic modulus and yield strength of alloys using textual inputs. Leveraging the pre-trained RoBERTa and BERT encoder model as its foundation, AlloyBERT employs self-attention mechanisms to establish meaningful relationships between words, enabling it to interpret human-readable input and predict target alloy properties. By combining a tokenizer trained on our textual data and a RoBERTa encoder pre-trained and fine-tuned for this specific task, we achieved a mean squared error (MSE) of 0.00015 on the Multi Principal Elemental Alloys (MPEA) data set and 0.00527 on the Refractory Alloy Yield Strength (RAYS) dataset using BERT encoder. This surpasses the performance of shallow models, which achieved a best-case MSE of 0.02376 and 0.01459 on the MPEA and RAYS datasets respectively. Our results highlight the potential of language models in material science and establish a foundational framework for text-based prediction of alloy properties that does not rely on complex underlying representations, calculations, or simulations. [ABSTRACT FROM AUTHOR]

With the aim of improving the excellent mechanical properties of the SLM-produced AlSi10Mg alloy, this research focuses on post-processing using ECAP (Equal Channel Angular Pressing). In our article, two different post-processing strategies were investigated: (1) low-temperature annealing (LTA) and subsequent ECAP processing at 150 °C; (2) no heat treatment and subsequent ECAP processing at 350 °C, 400 °C and 450 °C. The microstructure and mechanical properties of this alloy were analyzed at each stage of post-treatment. Metallographic observations, combined with SEM and EBSD studies, showed that the alloys produced by SLM have a unique cellular microstructure consisting of Si networks surrounding the Al-based matrix phase. Low-temperature annealing (LTA), followed by ECAP treatment, facilitated the microstructural evolution of the alloy with partial breakup of the Si network and observed nucleation of β-Si precipitates throughout the Al matrix. This resulted in a Vickers microhardness of 153 HV and a yield strength of 415 MPa. The main results show that post-processing of SLM-produced AlSi10Mg alloys using ECAP significantly affects the microstructural evolution and mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

In the present work, an attempt has been made to synthesize metal matrix composite using Al2024 as matrix material with Si3N4 particulates and K2TiF6 reinforcement using liquid metallurgy route in particular stir casting technique. The addition level of reinforcement is being varied from 4-8% in steps of 4 wt%. For each composite, reinforcement particles were preheated to a temperature of 500ºC and then dispersed in steps of three into the vortex of molten Al2024 alloy rather than introducing all at once, thereby trying to improve wettability and distribution. Microstructural characterization was carried out for the above prepared composites by taking specimens from central portion of the casting by microstructural studies and SEM analysis. Tensile, Impact, and Fatigue properties of the prepared composite were studied before and after addition of Al2024 particulates to note the extent of improvement. Microstructural characterization of the composites has revealed fairly uniform distribution of Si3N4 particulates and some amount of grain refinement in the specimens. SEM analysis revealed the presence of Si3N4 and other phases. Further, the Tensile and Impact strength of the composite found increased with increased filler content. [ABSTRACT FROM AUTHOR]

In this short review, we highlight instances where interstitials have been shown to substantially increase the yield strength and work-hardening rate (WHR) of f.c.c. alloys, particularly high entropy alloys, medium entropy alloys, TWIP steels and stainless steels. However, the common practice of describing interstitial strengthening in f.c.c. alloys using models that are used to explain substitutional strengthening appears to be neither appropriate nor accurate. Here we suggest, based on the literature, that the yield strength increase due to interstitials in f.c.c. alloys is more appropriately described by a linear dependence on the concentration: due to a paucity of experimental studies, the dependence of the yield strength and WHR on misfit parameters is currently unclear. Thus, the source of the strengthening remains unclear. A feature that has been observed in several f.c.c. alloys is that interstitial additions lead to a change from wavy to planar slip although the origin of this change, which may be related to changes in stacking fault energy as well as other factors, remains unclear. The paper concludes by outlining areas of future research, including the need to develop a new model for interstitial strengthening in f.c.c. alloys. [ABSTRACT FROM AUTHOR]

The AK5M2 aluminum alloy was investigated following surface modification involving deposition of a titanium film with subsequent electron beam irradiation. The strength characteristics of the alloy according to tension to failure are determined. Changes in the crystal lattice period of the Al and Al3Ti phases depending on the electron beam energy density are investigated and analyzed. Based on the experimental results, the most effective modes of electron beam processing were selected to increase the obtained mechanical properties of the alloy. [ABSTRACT FROM AUTHOR]

On the basis of the ternary phase diagram of Ti-Zr-Ta alloys and the d-electron orbital theory, the alloys with the nominal compositions of Ti-40Zr-20Ta (TZT1), Ti-35Zr-20Ta (TZT2) and Ti-30Zr-20Ta (TZT3) (in atom composition) were designed. The alloys were solution-treated (STed) at 1173 K for 3 h, and then aged (Aed) at 973 K for 6 h. The microstructure and mechanical properties of the three alloys were characterized. The results show that the three alloys comprised β-equiaxed grains after solution treatment at 1173 K for 3 h, and the β phases separated into β1/β2 phases by the spinodal decomposition in the alloys after being aged at 973 K for 6 h. The spinodal decomposition significantly promoted the yield strength of the alloys. For the TZT1 alloy, the yield strength increased from 1191 MPa (in the STed state) to 1580 MPa (in the Aed state), increasing by about 34%. The elastic moduli of the TZT1, TZT2 and TZT3 alloys after solution treatment at 1173 K were 75.0 GPa, 78.2 GPa and 85.8 GPa, respectively. After being aged at 973 K for 6 h, the elastic moduli of the three alloys increased to 81 GPa, 90 GPa and 92 GPa, respectively. Therefore, the spinodal decomposition can significantly promote the strength of the Ti-Zr-Ta alloys without a large increase in their elastic modulus. [ABSTRACT FROM AUTHOR]

The room temperature strength and hardness of TaW alloys limit their further development for engineering applications. In order to improve the room temperature mechanical properties of TaW alloys, Hf elements was selected to strengthen the traditional TaW alloys. The elastic constants and charge densities of Hf-doped TaW alloys were calculated by first-principles to reveal the strengthening effect. It was found that the Hf alloying obviously enhanced the hardness of TaW alloys, which was attributed to the formation of metallic and ionic bonds in the alloys. In order to verify the calculated results, hardness and compression tests were carried out for TaWHf alloys. The hardness and yield strength significantly increased with the increased of Hf elements, which was in good agreement with the first-principles calculation. Among them, yield strength of Ta-10.17 W-19.83Hf alloy was as high as 1220±8.4 MPa, twice larger than that of the normal Ta-10 W alloy without obviously sacrifice in plasticity. It was indicated that Hf alloying can effectively strengthen TaW alloys, which provided a guidance for the development of high-performance TaW alloys. • Ta-W-Hf alloys were designed and alloying Hf elements obviously strengthened Ta-W alloys. • The addition of Hf promoted the formation of metallic and ionic bonds in Ta-W alloys. • Compressive strength, yield strength and hardness of Ta-W-Hf alloys increased with increased of Hf content. • The calculated results were consistent with the trend presented by the experimental results. [ABSTRACT FROM AUTHOR]

In this work, the influence of different heat treatments (HT) processes on the microstructure and mechanical properties of cast Al–4Mg–1.5 Mg alloy was investigated. To investigate the effect of HT, firstly Al–4Cu–1.5Mg samples were homogenized (solution treatment) at 500 °C/2h, water quenched at room temperature (RT) and then immediately exposed to an artificial aging process at 200 °C for various aging times of 1, 4, 8, 12, 16, 20 and 24 hours. Quantitative examinations after HT processes (solution treatment and aging) have shown that intermetallic phases (Al2Cu and Al2CuMg) were dissolved in the α-Al matrix phase and distributed along the grain boundary. Some mechanical properties (HVσ, σTYS, σUTS, σCYS, E and δ) of a sufficient number of alloy samples exposed to different heat treatments were examined in detail. The data obtained show that the conditions of solution treatment and aging in some conditions show superior mechanical properties than the sample in the form as-cast. The highest microhardness value (126 HV) was obtained for the α-Al matrix phase, which was subjected to solution treatment (only homogenization). After aging for 1h at 200 °C, the peak value of microhardness was achieved as 289.5 HV for intermetallic phases. The highest tensile strength (σUTS) was obtained as 328 MPa for the sample which aged for 8h at 200 °C after solution treatment for 2h at 500 °C. [ABSTRACT FROM AUTHOR]

The effect of scandium content on the structure and properties of alloy Al – 4.5% Zn – 4.5% Mg – 1% Cu – 0.12% Zr is determined. The microstructure of the alloy is studied with identification of the phases using an optical microscope and scanning and transmission electron microscopes. The Vickers hardness and the yield strength under heating are determined. The phase diagram is plotted and the nonequilibrium crystallization is described using the Thermo-Calc software and the TTAL5 database. It is shown that addition of 0.1% scandium contributes substantially enough into the growth of the hardness after 3-h annealing at 450°C and into the yield strength after 20-h aging at 175°C. The compositions studied are recommended as a base for designing new refractory alloys based on the Al – Zn – Mg – Cu system. [ABSTRACT FROM AUTHOR]

Strength and hardness of metallic materials are reported to correlate in a specified form. Among various equations, yield strength is generally converted from Vickers hardness (HV) via a three‐time relation due to the simple and nondestructive nature of hardness testing. Herein, a through literature review is made and data of strength and HV for face‐centered cubic (FCC) and body‐centered cubic (BCC) high‐entropy alloys (HEA) are collected. The yield strength and HV visibly deviate from the three‐time relation, but the ultimate tensile strength and HV roughly follow the three‐time relation. New linear relationships, which are universally applied to convert HV to yield strength and ultimate tensile strength, are proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] Age strengthening is a common method to achieve superior mechanical properties employed in magnesium (Mg) alloys. However, the experimental approaches to examine the aging effects on mechanical properties are primarily based on trial and error, posing challenges for the design and development of high-strength Mg alloys. A promising solution to address this challenge is to establish an accurate prediction model for the aging effects on Mg alloys, covering the evolution of microstructure and corresponding mechanical properties. This paper introduces a multiscale simulation approach to accurately predict the aging effects on the Mg-2.3Zn (at.%) alloy. To begin, we establish a phase field model to simulate the microstructure evolution at 150 ℃, demonstrating precipitate growth during aging in alignment with experimental observations. Secondly, based on the microstructures obtained from phase field simulations, the corresponding yield strength is determined through finite element method simulations. The simulation successfully captures the peak-aged behavior of yield strength during aging, resulting in a yield strength of 167 MPa at the peak-aged state, with a deviation of less than 5 % from experimental results. In-depth analysis indicates that the peak value of total yield strength arises from the interplay between solid solution strengthening and precipitate strengthening. Furthermore, precipitate strengthening reaches a peak value at a specific aging time, deviating from the total yield strength. This deviation is primarily attributed to the effect of precipitate size on shear strengthening during aging. This study presents a general method for predicting the microstructure evolution and corresponding mechanical properties of alloys through multiscale simulations, offering valuable insights for designing and predicting the performance of metallic alloys. [ABSTRACT FROM AUTHOR]

As-cast alloys have the advantage of short forming processes, but there is currently a lack of research on systematic design alloys with better mechanical properties. Herein, combining a machine-learning with random forest model algorithm, a high-throughput alloy design framework under multidimensional constraints was used to discover new NiCoFeCrAlTi multi-principal element alloys (MPEAs) for superior tensile properties. The as-cast dual-phase Ni 28 Fe 32 Cr 25 Al 10 Ti 5 alloy with 1386 MPa of tensile yield strength and 1.8% uniform elongation was designed, which is much higher than the best value in the original training dataset. This apparent high strength can be attributed to the phase interfacial strengthening, in which the soft face-centered cubic (FCC) phase precipitated extensively aside the grain boundaries of hard body-centered cubic (BCC) matrix. The BCC matrix provides high strength and FCC precipitates play role in ductility. Machine learning is expected to be utilized for designing as-cast MPEAs with superior mechanical properties. • An uncomplicated tensile property-orientated materials design strategy was proposed. • The as-cast Ni 28 Fe 32 Cr 25 Al 10 Ti 5 alloy with 1386 MPa of tensile yield strength was designed. • This high strength can be attributed to the phase interfacial strengthening. • The dominant characteristic of Ni 28 Fe 32 Cr 25 Al 10 Ti 5 HEA was that fine lamellar and granular FCC phase intricately intertwined at the grain boundary of BCC phase. [ABSTRACT FROM AUTHOR]

To support the development of refractory complex, concentrated alloys (RCCAs), a clear understanding of the effect of temperature on strength is needed. Body-centered cubic (BCC) refractory metals and dilute refractory alloys show a strong temperature dependence of yield stress (σ y) at low and high temperatures, with a relatively temperature-independent regime in between. RCCAs may introduce important changes in deformation and strengthening mechanisms, so it is not clear if RCCAs will show the same thermal dependencies. The objective of this work is to answer the question, "Is the temperature dependence of strength similar or different for RCCAs compared to BCC refractory elements and dilute refractory alloys ?" We evaluate σ y vs. temperature for 61 RCCAs by analyzing data curated from the literature. We find that σ y increases progressively from refractory BCC elements, to dilute alloys, to single- and multi-phase RCCAs. Single-phase RCCAs show the same three thermal regimes, but the stresses are higher and the intermediate plateau is shorter and is sometimes steeper. The thermal dependence of σ y in multi-phase RCCAs shows more substantial differences. Six factors that contribute to the higher σ y of RCCAs are discussed: (i) higher solute concentration; (ii) dispersion in atomic sizes; (iii) the shear modulus magnitude; (iv) the type of principal elements; (v) the solvus temperature of predicted secondary phases; and (vi) microstructure. Based on the present observations and analyses, suggestions for future research are made, especially regarding improved models for the effect of temperature on strength. [Display omitted] [ABSTRACT FROM AUTHOR]

The phase component, microstructure and compressive properties of a novel high entropy alloy, Al0.5CuFeNiV in as-cast and annealed conditions were investigated. Its phase structure is composed of FCC+B2 (ordered BCC) phase in both states. The ordered BCC phase is the major dendritic phase depleted with Cu, while the FCC phase is enriched with Cu, forming a netlike framework. Moreover, the alloys in both states possess a promising trade-off in strength and ductility. Specifically, the yield strength and the elongation of the as-cast alloy are 1456MPa and 10.0%, respectively. After annealing, the strength decreases to 861 MPa, while the elongation increases to 15.5%. The combination of phase constitution, microstructure morphology, and solid solution strengthening was conducted to explain their mechanical behavior. [ABSTRACT FROM AUTHOR]

The yield strength of random metal alloys, i.e. alloys with random occupation of the crystalline lattice sites by the elemental constituent atoms all considered as solutes, is primarily understood as controlled by solute/dislocation interactions. Solute-solute interactions exist and provide the energetic driving force for both short-range and long-range order but can then also affect yield strength even in the random alloy. Here, a recent theory for random alloys is extended to include solute-solute interactions described by pair-wise interactions. The new theory involves the standard deviation in total solute-solute interaction energies as a dislocation segment glides through the material, which changes specific solute-solute pairs across the glide plane at every pair distance. An analytic expression is derived for the above standard deviation and validated against numerical simulations on a wide range of model random alloys consisting of 2–5 elements interacting via Lennard–Jones pair potentials. The theory is applied to the bcc MoNbTaW high entropy alloy, using solute-solute interactions computed via first-principles, and a model NbTaV alloy, described by EAM potentials, where the strength increases negligibly by 2% and 0.45%, respectively. Application to random dilute fcc Ni-Al, where the first-neighbor Al-Al interaction is very strongly repulsive, shows significant strengthening of 60–100% at 10% Al, depending on the origin of the inputs. Some connections to literature atomistic simulations on Ni–Al are also presented. Overall, the present theory provides a quantitative framework for assessing the relative roles of solute-dislocation and solute-solute interactions on strengthening in random alloys. [ABSTRACT FROM AUTHOR]

The mechanical properties of a high-entropy CrMnFeCoNi2Cu alloy with an FCC lattice have been studied in a broad temperature range (4.2–350 K). The microhardness and Young's modulus were measured at 300 K for two structural states. The temperature dependences of the yield strength, deforming stress, and strain rate sensitivity have been obtained. It was found that a high-strength state is realized in the alloy while maintaining high plasticity, over the entire temperature range. Empirical estimates of microscopic plasticity parameters and internal and effective stresses have been obtained using the thermally activated deformation model. [ABSTRACT FROM AUTHOR]

Recent experiments show that the CoCrFeNiPd high-entropy alloy (HEA) is significantly stronger than CoCrFeNi and with nanoscale composition fluctuations beyond those expected for random alloys. These fluctuations were suggested to be responsible for strengthening. Here, a recent parameter-free theory for initial yield strength in fcc random alloys is shown to predict the strength of CoCrFeNiPd in good agreement with experiments. The strengthening is due mainly to the large misfit volume of Pd in CoCrFeNi, indicating that effects of the non-random composition fluctuations are secondary. Analyses of strength variations and strengthening-associated length scales helps rationalize why dislocation motion is insensitive to such fluctuations. These findings point to the value of theory for understanding mechanical behavior of HEAs. Experiments and theory are highlighting chemical ordering in high-entropy alloys (HEAs) as important for mechanical properties but the high strength in CoCrFeNiPd is predicted here to be achievable in the random alloy due to the large misfit volume of Pd, in spite of observed ordering. Ordering is thus not essential for attaining high-strength HEAs. [ABSTRACT FROM AUTHOR]

The element Vanadium (V) appears unique among alloying elements for providing high strengthening in both the fcc Co-Cr-Fe-Mn-Ni-V and bcc Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr high-entropy alloy families. The origin of Vanadium's special role is its atomic volume: large in the fcc alloys and small in the bcc alloys, and thus having a large misfit volume in both crystalline structures. A parameter-free theory applicable to both fcc and bcc HEAs rationalizes this finding, with predictions of strength across a range of fcc and bcc alloys in quantitative and qualitative agreement with experiments. In the fcc class, the analysis demonstrates why the newly-discovered NiCoV and Ni 0.632 V 0.368 alloys have far higher strength than any other fcc alloy and are predicted to be the highest attainable. In the bcc class, the analysis demonstrates that the addition of V always increases the strength relative to the same alloys without V. The optimization of complex alloys for high strength should thus center around the inclusion of V as a primary element at concentration levels of around 25 at.% [ABSTRACT FROM AUTHOR]

7075 alloys were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified upwards under various growth velocities (8.3–166.0 μm/s) using a Bridgman-type directional solidification furnace. Dendritic spacings (λ1, λ2) and microhardness (HV) were measured from both longitudinal and transverse sections of the samples. Ultimate tensile strength (σU) and yield strength (σy) of the solidified samples at room temperature were examined. The HV increased from 75.2 to 112.8 MPa, the σU increased from 155.8 to 210.1 MPa, and the σy increased from 198.4 to 319.8 MPa with increasing growth velocity from 8.3 to 166.0 μm/s. Exponent values of the V for the λ1, λ2, HV, σU and σy were calculated as 0.27, 0.41, 0.05, 0.11 and 0.15, respectively. The results show that the hot tearing in the 7075 alloy is caused by the fracture of dendrites structures. [ABSTRACT FROM AUTHOR]

We demonstrate the formation of a hierarchical microstructure by optimized combination of Mo-doping and thermo-mechanical processing in a NiCoCr medium-entropy-alloy (MEA) that results in a significant improvement in yield-strength (~775 MPa) and ultimate-tensile-strength (~1200 MPa) with an elongation to fracture up to 35%. Addition of Mo slows down the recrystallization kinetics of the cold-rolled alloy at 700 °C. After 4 h annealing, the microstructure comprises soft recrystallized and hard non-recrystallized zones, dispersed σ precipitates, annealing twins and retained stacking faults/nanotwins that are shown to contribute to the overall mechanical behavior. Unlabelled Image [ABSTRACT FROM AUTHOR]

A theory for strengthening for multicomponent non-dilute alloys possessing short-range order (SRO) has recently been developed. The theory predicts that, in addition to a well-known athermal strengthening, there is a notable effect of SRO on the solute–dislocation interactions that can decrease or increase the strength relative to a random alloy. Here, carefully designed atomistic simulations in a model binary NbW alloy are used to demonstrate that alloy strength due to solute–dislocation interactions can be increased or decreased, depending on the SRO and consistent with theoretical predictions. Specifically, SRO is introduced using fictitious solute–solute interactions in an alloy system with very small true solute–solute interactions, and the Nudged Elastic Band (NEB) method is then used to compute the energy barriers for edge dislocation motion for various levels of SRO. Energy barriers, and hence alloy strengths, can be decreased when the Warren-Cowley SRO parameters are negative (attraction of unlike solutes). The theoretical predictions for the same system are in reasonable quantitative agreement with the simulation results. These findings demonstrate the unexpected possibility of reduced strength due to SRO and also further validate the analytical theory as a tool to guide alloy design. [Display omitted] [ABSTRACT FROM AUTHOR]

Recent surging interest in strengthening of High Entropy Alloys (HEAs) with possible chemical ordering motivates the development of new theory. Here, an existing theory for random alloys that accounts for solute-dislocation and solute–solute interactions is extended to include strengthening due to short-range order (SRO). Closed form expressions are presented for the yield strength and energy barrier of dislocation motion in alloys with SRO based on inputs of atomic misfit volumes, average lattice and elastic constants, the SRO parameters, and effective pair interactions between solutes. The theory shows both the long-established athermal strengthening effect of SRO as well as a notable effect of SRO on the misfit volume strengthening, which can increase or decrease strength. The generalized solute-strengthening theory is the most comprehensive to date that is applicable to macroscopically homogeneous single-phase alloys using inputs that can be measured, computed, or estimated. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of thermal ageing time and temperature used during heat-treatment were studied on tensile strength, elongation, and microhardness of the laser welded Nb-1%Zr-0.1%C alloy in continuous wave mode. Post-weld heat treatment (PWHT) was carried out by varying the temperature and time in the ranges of (850–1050) °C (that is, about the recrystallisation temperature) and (0.5–4) h (as the weld samples were prepared in the form of sheets), respectively. The grain sizes of fusion zone (FZ), and FZ heat treated at 850 °C for 4 h and that at 950 °C for 2 h were found to be equal to 52.85 μm, 84.89 μm and 116.43 μm, respectively. The segregation of zirconium, carbon and oxygen increased grain boundary energy and induced brittleness to the grain boundary, resulting in loss of ductility. The micro-hardness and Young's modulus values were observed to increase in the FZ compared to that of the base metal (BM), but their decreasing trends were noticed during the heat-treatment due to the grains' softening. For the PWHT samples, the plasticity was found to decrease to about 57% of that of BM. This was attributed to the precipitation of carbides, grain growth, and dislocation pinning during the ageing process. During the heat-treatment of the welded samples, both Yield Strength (YS) and Ultimate Tensile Strength (UTS) were found to decrease to 77% and 86%, respectively, of that of the BM. • Deals with laser welding of Nb-1%Zr-0.1%C alloy. • Studies the effects of heat-treatment on mechanical properties. • Heat-treatment of the weld decreases YS and UTS • Heat-treatment of the weld decreases plasticity. • Heat-treatment decreases the micro-hardness and Young's modulus of the weld. [ABSTRACT FROM AUTHOR]

In the present study compressive strength data and room temperature (RT) deformability of three V-rich V–Si–B alloys are reported. All alloys were taken from the V SS (V solid solution)-V 3 Si-V 5 SiB 2 three-phase region of the respective phase diagram and differ in their primary solidification phase of either V SS , V 3 Si or V 5 SiB 2. The RT yield stresses were determined by the 0.2% offset method and the plastic strain was obtained by subtracting the combined compliance of the testing machine and the specimen from the individually measured load-displacement curves. The microstructures in the as-cast and deformed state were analyzed using SEM, EBSD and TEM. Dislocation activity was only observed in the V SS phase while the intermetallic phases were dislocation-free. Thus, the RT plasticity in V-rich V–Si–B alloys is mainly governed by the volume fraction of the V SS phase. Hence, the alloy containing primary V SS dendrites has the highest plastic strain compared to the V 5 SiB 2 and V 3 Si primary crystallizing alloys. Investigations of the V SS phase on binary V–Si alloys reveal that silicon acts as solid solution strengthener, but ductility of the V SS phase is retained throughout the solubility range. The present results are quite astonishing since Mo–Si–B alloys containing similar amounts of Si and B are known to be fairly brittle at RT. Image 1 [ABSTRACT FROM AUTHOR]

Bulk hardness and tensile properties of an AA6063 Al-Mg-Si alloy specimens subjected to artificial age-hardening treatment over a wide range of temperatures (373-523 K) and time durations (5 min to 60 days) have been determined and analyzed to predict complete aging kinetics and yield strength. The predictions have been made using simplified hardness-based models. The experimental results are used to generate kinetic models for under- and overaging regimes following the Johnson–Mehl–Avarami and the Lifshitz–Slyozov–Wagner equations, respectively. The obtained kinetic parameters are found to satisfactorily describe the overall aging kinetics of the Al-Mg-Si alloy. Additionally, relationship between the estimated hardness and the yield strength values of the AA6063 alloy has been established and its utility has been validated. The developed hardness-based models can be used as convenient tool to determine the state of aging and to predict the yield strength of Al-Mg-Si alloy. [ABSTRACT FROM AUTHOR]