Thermodynamic and mechanical properties of 15 single-phase and 11 multi-phase refractory complex concentrated alloys (RCCAs) are reported. Using the CALPHAD approach, phase diagrams for these alloys ...are calculated to identify the solidus (melting, Tm) temperatures and volume fractions of secondary phases. Correlations were identified between the strength drops at 1000 °C and 1200 °C and the alloy compositions, room temperature properties, melting temperatures and volume fractions of secondary phases. The influence of alloy density on the temperature dependence of specific yield strength was also explored. The conducted analysis suggests that the loss of high-temperature strength of single-phase BCC RCCAs is related to the activation of diffusion-controlled deformation mechanisms, which occurs at T ≥ 0.6 Tm, so that the alloys with higher Tm retain their strength to higher temperatures. On the other hand, a rapid decrease in strength of multi-phase RCCAs with increasing temperature above 1000 °C is probably due to dissolution of secondary phases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This data article presents the compilation of mechanical properties for 370 high entropy alloys (HEAs) and complex concentrated alloys (CCAs) reported in the period from 2004 to 2016. The data sheet ...includes alloy composition, type of microstructures, density, hardness, type of tests to measure the room temperature mechanical properties, yield strength, elongation, ultimate strength and Young׳s modulus. For 27 refractory HEAs (RHEAs), the yield stress and elongation are given as a function of the testing temperature. The data are stored in a database provided in Supplementary materials, and for practical use they are tabulated in the present paper. The database was used in recent publications by Miracle and Senkov 1, Gorsse et al. 2 and Senkov et al. 3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
While ordered L12 or gamma prime precipitates in face centered cubic (FCC) based microstructures have been extensively used for strengthening nickel or cobalt base superalloys, and more recently in ...high entropy alloys (HEAs) or complex concentrated alloys (CCAs), the possibility of exploiting ordered B2 precipitates in FCC-based systems has been relatively less investigated. The present study shows the propensity of developing a heterogeneous microstructure, consisting of two different distributions of FCC grain sizes, and two different size scales of B2 precipitates, within an FCC-based Al0.5Co1.5CrFeNi1.5 HEA/CCA. This alloy composition has been designed using solution thermodynamics-based modeling such that it has a high phase fraction and solvus temperature of the B2 phase. The resulting heterogenous microstructure exhibited an approximately 400% increase in yield strength with respect to the single-phase FCC solid solution condition of the same alloy while maintaining very good tensile ductility ∼20%.
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•The HEA/CCA Al0.5Co1.5CrFeNi1.5 has been identified as a candidate alloy for studying FCC + B2 microstructure.•Single phase FCC, FCC + L12 and FCC + B2 microstructures have been obtained in this alloy via thermomechanical processing.•Precipitation annealing directly after rolling resulted in a heterogeneous microstructure with multiple length scales of B2.•The heterogeneous microstructure results in a 400% increase in yield stress when compared to the single phase FCC condition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An examination of a compositionally graded AlxCuCrFeNi2 high entropy alloy (HEA) or complex concentrated alloy (CCA), revealed that marginally increasing Al content from x=0.8 to x=1.0 (+6at.%) ...changes the primary solidification phase from a simple disordered-fcc to a bcc-based ordered-B2 phase. Subsequently, a second solidification product forms, a disordered-bcc in case of x=0.8 and a disordered-fcc in case of x=1.0. Solid-state decomposition within these phases results in fcc+L12 and bcc+B2 products, accompanied by compositional partitioning. These results provide new insights into the influence of Al on the primary solidification product, and have been rationalized using a computational thermodynamic approach.
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Guided by solution thermodynamic modeling coupled with detailed experimental characterization, the present study establishes that the alternating FCC and BCC lamellar microstructure in the ...Al0.7CoCrFeNi high entropy alloy, is a result of non-equilibrium partitionless solidification from the liquid to single B2 phase, followed by solid-state decomposition. Widmanstätten FCC lamellae form from the allotriomorphic FCC precipitates at the B2 grain boundaries, leading to a lamellar microstructure, divided into two distinct sub-systems. Isothermal annealing further drives these individual sub-systems towards equilibrium via precipitation of ordered intermetallic phases. The transformation in FCC lamellae initiates by the formation of metastable L12 precipitates at shorter annealing times, which are eventually replaced by the equilibrium BCC and B2 phases, forming composite B2+BCC laths, on long term annealing. These results further exemplify that interesting transformation pathways lead to hierarchical microstructures within HEAs, and the fact that as processed conditions in these alloys are often far-from equilibrium.
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•We design a novel high conductivity-high strength materials Cu-based alloys.•The designed Cu–Mg alloys represent a good alternative to the Cu–Be alloys.•We calculate the strengthening contributions ...arising from microstructure parameters.•Eutectic islands and high precipitates density favor excellent balance of properties.
Some novel high conductivity–high strength materials were designed in the binary Cu–Mg. They exhibit an excellent balance between strength and electrical properties. The properties and the performance of the designed materials are compared with the main Cu-based alloys and the analysis shows that they perform equally to the best one (Cu–Be). Furthermore, we show that an increase of Mg content modifies the microstructure feature and leads to a strong increase of strength without any significant deterioration of the electrical conductivity. This behavior was attributed to the formation of eutectic islands in which high density of Cu2Mg nanoparticles precipitate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this paper, the crystal structure, microstructure, thermoelectric properties and figure of merit (zT) of highly pure higher manganese silicide (HMS) alloys are reported and discussed without the ...bias generally introduced by impurities in published results. The alloys were produced by both solid-state reaction diffusion assisted by spark plasma sintering and conventional arc melting in order to evaluate the effect of the process on the microstructure and on the resulting properties of HMS. The effect of Ge addition is also explored. Properties diagram for thermoelectric materials is displayed to assess the performance of un-doped and Ge-doped HMS alloys in comparison with the state of the art. Electrical conductivity and zT at 500 °C of the HMS alloys studied here exceed published properties achieved with similar alloys, providing new process options for reliable, affordable and efficient thermoelectric applications.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Varying the Al content, strongly influences the microstructure, magnetic and microhardness of additively manufactured Alx(CoFeNi) (x = 0, 10, 30) complex concentrated alloys (CCA). Compared to the ...single FCC phase of CoFeNi, the hierarchical FCC/L12+BCC/B2 heterostructure of heat treated Al10(CoFeNi) CCA displayed substantially improved saturation magnetization, Curie temperature and microhardness. However, there was no significant change in the properties of heat treated CoFeNi and Al30(CoFeNi) CCA. These findings can be rationalized via thermodynamic modelling of the phase stability. We have demonstrated the feasibility of exploiting additive manufacturing for rapidly screening and developing novel high-performance alloys for next generation rotating electrical machines.
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•Thermodynamic, physical and mechanical properties were correlated for RCCAs.•Criteria for the selection of strong and ductile refractory alloys were proposed.•A multivariate linear ...regression model was developed for RCCAs.•This model was used to predict new RCCAs for high-temperature applications.
Correlations were explored between mechanical, thermodynamic and physical properties of refractory complex concentrated alloys (RCCAs). Experimentally measured yield strengths (σy) and ductility were taken from the open literature and were compared against liquidus, solidus and solvus temperatures, elastic properties (Young’s, shear and bulk moduli), density (ρ), surface energy (γ) and valence electron concentration (VEC). If not publicly available, the thermodynamic properties were calculated using CALPHAD while the other properties listed above were estimated using a rule-of-mixtures average of the constituent element properties. This analysis emphasized tensile ductility. Based on the identified correlations, useful criteria for selecting possibly ductile RCCA compositions with good high-temperature strength were proposed, a few ductile and strong RCCAs were made and properties of some of them were reported in this paper. Additionally, multivariate linear regression (MLR) was used to identify new insights from the high dimensional space of the present study by modeling the influence of composition and the input thermodynamic and physical properties on the high-temperature strength and room temperature ductility. Equal concentrations of Mo and Nb in RCCAs were found to give a good balance of strength and ductility. The MLR analysis identified over 50 promising RCCAs for intended high-temperature applications, pending experimental confirmation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In situ Ti-6Al-4V/TiB discontinuously reinforced composites, containing 20 and 40% of TiB whiskers by volume, were produced by blending Ti, Al/V, and TiB
2 powders. The consolidated powder blends ...were annealed to transform the TiB
2 particles to TiB. The microstructural evolution of the composite was studied as a function of heat treatment duration at 1100, 1200, 1300 and 1400 °C. The mechanical properties of Ti-6Al-4V/TiB composites were established in tension and compression at room temperature and 300 °C, and by resonant ultrasound spectroscopy (RUS), for the two volume fractions of TiB, and for randomly oriented and aligned arrays of TiB whiskers. The average Young’s modulus of the composite with 20% of randomly oriented TiB whiskers was 153 GPa, compared to 109 GPa for unreinforced Ti-6Al-4V. The average Young’s modulus of composites with 20 and 40% of aligned TiB whiskers was measured along the extrusion axis as 169 and 205 GPa, respectively. The stiffness of TiB whiskers was determined from bulk measurements with the Halpin-Tsai equation to be 482 GPa. Yield and ultimate strengths near 1200 MPa were measured. The strength and ductility of the materials were limited in the present study by non-optimal matrix microstructure and inadequate particulate distribution, and approaches for properties improvements are provided.
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