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The effect of H+‐ion irradiation on the structure and properties of a Cu50Zr50 metallic glass (MG) is investigated. High‐energy synchrotron X‐Ray diffraction results indicate that the glass maintains its amorphous nature after ion irradiation. As the ion fluence increases, the atomic bond length of MGs becomes shorter, whereas the nanohardness and Young's modulus increase from 7.08 ± 0.01 and 111.3 ± 1.1 GPa for the as‐spun sample to 8.59 ± 0.06 and 123.1 ± 1.3 GPa for the sample irradiated with 2 × 1016 cm−2 fluence. The corrosion potential of the studied MG in 1 mol L−1 HCl increases from −0.5953 to −0.4519 V, suggesting an enhanced corrosion resistance of MGs after ion irradiation. The modification of mechanical properties and corrosion resistance can be interpreted from the ion irradiation‐induced structural evolution. The results obtained herein can be beneficial for better understanding the mechanical properties and corrosive behaviors of MGs under extreme conditions like ion irradiation, thus promoting their industrial applications. [ABSTRACT FROM AUTHOR]

Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabricated by the conventional copper mould casting method. The supercooled liquid region Δ T x, reduced glass transition temperature T rg, γ parameter, and δ parameter of the alloy were measured to be 63.9 K, 0.561, 0.393, and 1.400, respectively, implying that the alloy has an excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns, typical of bulk glassy alloys. [ABSTRACT FROM AUTHOR]

Metallic additive manufacturing (AM) offers near net-shape fabrication but often results in insufficient strength and/or ductility due to voids or cracks, coarse initial crystalline microstructure, insufficient volume fraction of precipitates and yet post-AM strengthening/toughening methods non-destructive to shape are generally lacking. Here, we report a laser-directed energy deposited (L-DED) medium entropy alloy (MEA) with a heterostructure (HS) comprising alternate layers of solid-solution and intermetallic-dispersed MEA that possess ultimate tensile strength of 1132.8 MPa and elongation of 50.6 %, corresponding to strength-ductility synergy higher than other medium- or high-entropy alloys reported. The multilayers were produced from a dual source of CoCrNi MEA powder and a powder mixture of the same MEA, Al and Ti with stoichiometry (CoCrNi) 86 Al 7 Ti 7 , and the remarkable strength-ductility synergy is achieved only after post-L-DED heat treatment, which causes Al and Ti to diffuse across the layers to form a low-gradient HS. The significant back stress due to the HS contributes to the high strength, while the high ductility results from a high strain-hardening rate suppressing necking. This study demonstrates the concept of using AM not just as a near net-shape fabrication method but also a unique tool to produce low-gradient HSs with superb mechanical properties, via the use of multiple powder sources combined with suitable shape-preserving post-fabrication heat treatment. [Display omitted] • A layered heterostructure medium entropy alloy was fabricated by laser directed energy deposition. • The gradient distribution of L1 2 and σ phases at the layer interface is realized by heat treatment. • The synchronous improvement of strength and ductility results from precipitation hardening and back stress strengthening. [ABSTRACT FROM AUTHOR]

Abstract: Conventional crystalline materials usually exhibit a ductile to brittle transition behaviour at low temperatures. An increase in the strength is always accompanied by a decrease in the plasticity. Here the authors report on a significant enhancement in both compressive strength and plasticity of a Ti-based bulk metallic glass (BMG) deformed at low temperatures. The ductilization of the BMG system can be evidently attributed to the formation of dense shear bands and the rotation mechanism of shear bands. The cryogenic surroundings can effectively slow down the mobility and diffusion of the atoms and consequently, suppress the nucleation and growth of nanocrystals during the deformation process, allowing the simultaneous improvement in the mechanical responses of the glassy alloy to compressive loading far below the ambient temperature. [Copyright &y& Elsevier]

To control the grain growth of nanocrystalline WC–Co cemented carbides by phosphorus (P) doping was studied in spark plasma sintering (SPS). Experimental results show that the use of small amount of phosphorus dopant to chemically-activated sintering of the nanocrystalline WC–Co composites could enhance the sinterability, promote the low temperature densification, and decrease the sintering temperature of the WC–Co nanocomposites. With only 0.3 wt.% P additions, full density WC–7Co cermets were obtained at temperature as low as 1000 °C, which is 100 °C lower than that of the undoped counterparts in spark plasma sintering of the nanocomposites. By phosphorus doping in WC–Co nanocomposites, the grain growth of WC–Co cemented carbides could be inhibited to some extent, as a result WC–7 wt.% Co–0.3 wt.% P cemented carbides with average WC grain size of 200 nm were achieved, which can be attributed to the lower sintering temperature resulting in a decrease of grain boundary mobility. Mechanical properties measurements show that P doping could lead to a great increment of hardness, but at the same time a little sacrifice of fracture toughness of the nano-WC–Co cemented carbides. [Copyright &y& Elsevier]

Carbon nanotubes-nano-WC-Co composites were prepared by spark plasma sintering process. The preparation steps involving purified carbon nanotubes were stirred into the nano-WC-Co particles in alcohol using ultrasonic shaker, then ball milled for 60 min. The densification and grain growth behavior, the mechanical properties of the nanocomposites were investigated. Experimental results show that with small amount of carbon nanotube additions, the density of the composites can be enhanced but the grain size has marginal increase; the sintered nanocomposites combine superior hardness to toughness relationships over that of the pure nanocrystalline WC-Co cermets fabricated under the same process. The reasons for the increments can be due to the extraordinary mechanical properties of carbon nanotubes, the toughing and bonding role of carbon nanotubes occurred in the nano-WC-Co matrix, as well as the spark plasma sintering technique used. [Copyright &y& Elsevier]

• A β-solidifying TiAl alloy reinforced with ultra-fine yttrium-rich precipitates was consolidated by spark plasma sintering. • This TiAl alloy with refined duplex microstructure exhibited excellent tensile properties at room temperature. • Two types of yttrium-rich precipitates were detected, and the crystallographic relationship between them and γ-TiAl matrix were determined. A β-solidifying TiAl alloy with a refined microstructure and ultra-fine yttrium-rich precipitates that was consolidated by spark plasma sintering was investigated by scanning and transmission electron microscopies. Two categories of yttrium-rich precipitates, Y 2 O 3 and YAl 2 , with sizes ranging from tens to hundreds of nanometers were found to be dispersed within the matrix uniformly. The crystallographic relationship between the two precipitates and the γ-TiAl matrix was determined by the selected area electron diffraction and high-resolution transmission electron microscopy. This spark plasma sintered TiAl alloy was characterized by a uniform duplex microstructure, and it exhibited excellent tensile properties at room temperature. Typically, specimen sintered at 1150°C has an ultimate tensile strength of 1113.1 MPa, yield strength of 881MPa, and a moderate plastic elongation of 1.41%. Image, graphical abstract [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel high-entropy alloy CoCrFeNi microfibers with heterogeneous gradient structures was developed. • The CoCrFeNi microfibers displays an excellent strength–ductility combination both at 293 K and 150 K. • The deformation mechanisms of the microfibers at ambient and cryogenic temperatures are revealed. Exploring metallic microfibers with an excellent combination of high strength and ductility is a challenge for structural applications under extreme conditions. In this work, a heterogeneous gradient structure was introduced into CoCrFeNi high-entropy alloy (HEA) microfibers via thermomechanical processing. The annealed CoCrFeNi microfiber displays an ultrahigh yield strength of ∼ 1 GPa, an ultimate tensile strength of 1.45 GPa, and an outstanding uniform elongation of 75% at 150 K. These excellent properties originate from the ultrafine grains and heterogeneous gradient structure, as well as the activation of multiple deformation mechanisms including deformation twins, dense dislocations, stacking faults, Lomer-Cottrell locks, phase transformation and 9R phase. Our work not only suggests that HEA microfibers have great potential for structural applications in cryogenic environments, but also sheds light on the design of advanced multi-component metallic microfibers with superior mechanical properties. [ABSTRACT FROM AUTHOR]

The influence of annealing temperature on microstructure evolution and mechanical properties of CoCrFeNiMn 0.75 Cu 0.25 high-entropy alloy (HEA) was systematically investigated. As the annealing temperature increases, the grain becomes coarser, Cr-rich phase precipitates, and annealing twins appear in the matrix. The low angle grain boundary (LAGB) changes to high angle grain boundary (HAGB), which reduces the strength and increases the ductility of the studied HEA. The deformation bands, grain boundaries, and triple junctions of the grains are the preferred recrystallized nucleation sites. Based on the microstructural evolution, the contribution of the Cr-rich phase, LAGBs, HAGBs, and twin boundaries to the yield strength was analyzed by the modified Hall-Petch equation. These results may provide some guidance on tailoring the microstructures and mechanical properties for superior HEAs design. • The influence of annealing temperature on the microstructure and mechanical properties of a rolled HEA was discussed. • The deformation bands, grain boundaries, and triple junctions are the preferred recrystallized nucleation sites. • The microstructural evolution, and the contribution of LAGBs, HAGBs, and TBs to the yield strength was analyzed. [ABSTRACT FROM AUTHOR]

Tailoring microstructure and mechanical properties of structural materials to meet application requirements is a long-standing challenge in materials science. Here we have studied the effects of laser energy density (LED) on the microstructure and mechanical properties of single-track CoCrFeMnNi high entropy alloy (HEA) samples fabricated by laser directed energy deposition (LDED). The results indicate that the molten pool size of the single-track HEA samples gradually increases with increasing LED. All of the samples possess a single face-centered cubic (FCC) solid solution structure. The microstructures of the single-track HEA samples are mainly composed of columnar and equiaxed grains, and as the LED increases, their grain size increases while the micro-hardness decreases. Additionally, the relationship among the processing parameters, cooling rate and grain size was investigated via combining the numerical simulation and experimental observations. This work provides mechanistic insights into establishing the processing-structure-property relationships in the additively manufactured HEAs and contributes to achieve LDED of tunable HEA parts with desired microstructure and mechanical performance. [Display omitted] • LDED was utilized to manufacture the CoCrFeMnNi HEA with different laser energy densities. • The effects of laser energy density on microstructure and mechanical properties were studied. • The processing-structure-property relation for LDED of HEA was established. [ABSTRACT FROM AUTHOR]

Pre-straining was carried out on a CuZrAl bulk metallic glass (BMG), in order to understand the physical correlation between its structural heterogeneity and nano-mechanical performance. As the pre-strain increases, the studied glass remains its amorphous structure whereas the degree of local order firstly decreases and then increases, yielding a minimum value at 10 % pre-strain, and the Helmholtz activation energy (Δ F *), shear transformation zone (STZ) volume, number of atoms in the STZ (N), and the nanohardness value exhibits a similar trend. The variation in the structure and thus mechanical performance induced by pre-straining has been interpreted from the viewpoint of free volume concept. The results obtained here can be beneficial for tailoring the structure and the corresponding mechanical properties of BMGs. [Display omitted] • The physical correlation between the structure heterogeneity and nano-mechanical performance of a CuZrAl metallic glass is established. • The CuZrAl metallic glass with a pre-strain of 10 % exhibits the smallest local order degree, Helmholtz activation energy, shear transformation zone (STZ) volume, number of atoms in the STZ, and the nanohardness. • The variation in the structure and thus mechanical performance caused by pre-straining has been explained from the viewpoint of free volume concept. [ABSTRACT FROM AUTHOR]

Here, the effect of ion irradiation on the structure and mechanical properties of a Ti-based metallic glass has been studied. The samples maintains amorphous nature after ion irradiation. The irradiated glass exhibits higher hardness and Young’s modulus, and higher indent load at first pop-in event, which can be interpreted from the perspective of atomic-scale structural evolution. The results obtained here indicate that ion irradiation can be considered as a powerful method to finely tune the microstructure and properties of metallic glasses. [ABSTRACT FROM AUTHOR]

Bulk metallic glass (BMG), Zr 46 Cu 37.6 Ag 8.4 Al 8 (ZrCuAlAg), has been systematically evaluated in terms of microstructure, compressive properties, and wear resistance, aimed at exploring its use as a novel biomedical material. For comparison, the above-mentioned tests were also performed on Zr 51.9 Cu 23.3 Ni 10.5 Al 14.3 , Zr 51 Ti 5 Ni 10 Cu 25 Al 9 , and Ti 40 Zr 25 Ni 12 Cu 3 Be 20 BMGs, pure Ti and Ti–6Al–4V alloy. ZrCuAlAg BMG exhibits higher strength, higher hardness, and better wear resistance than other materials. All the results imply that the Ag-bearing ZrCuAlAg BMG with excellent mechanocompatibility will open up a new path for biomedical applications. [ABSTRACT FROM AUTHOR]

• TA15 titanium alloy was fabricated by EBSM with different parameters. • Basketweave structure and Widmanstatten structure were co-existed in EBSM-built samples. • Process window of martensite phase α′ in EBSM-built TA15 samples was obtained. • Samples with a mixture of (α′ + α + β) phases process a higher strength and lower plasticity than that with fully lamellar (α + β) phases. Ti6.5Al2Zr1Mo1V was fabricated via electron beam selective melting (EBSM) with different process parameters to study the diversity of microstructure. Results demonstrate that samples with a flat surface can be obtained when the ratio of beam current to scanning speed fluctuated between 5.0 and 7.5 as other parameters were fixed. Basketweave structure and Widmanstatten structure were observed to co-exist in EBSM-built samples under different parameters, while martensite phase α′ was more likely to form under low beam current and high scanning speed. Samples with a mixture of (α′ + α + β) phases possess a higher strength and lower plasticity than that with fully lamellar (α + β) phases due to the stress concentration at the α′/β interface in inhomogeneous microstructure. [ABSTRACT FROM AUTHOR]

Abstract: Mg–5Y–3Nd–0.6Zr–xGd (x =0, 2 and 4wt.%) alloys were prepared by metal mould casting technique, the structures and mechanical properties were investigated. The alloys were mainly composed of α-Mg solid solution and β-phase. With increasing Gd content, Mg5RE phase increased and the grain was refined. The Mg–5Y–3Nd–2Gd–0.6Zr alloy exhibited highest ultimate tensile strength and Mg–5Y–3Nd–0.6Zr alloy showed highest yield strength at room temperature. With increasing amount of Gd, the thermal resistance was improved. The Mg–5Y–3Nd–4Gd–0.6Zr alloy exhibited highest UTS and YS at 250°C, they were about 1.27 times higher than those of Gd-free alloy, which was mainly attributed to the increase of the β-phase and Mg5RE strengthening phase. [Copyright &y& Elsevier]

Abstract: Mg–4Al–4Nd–0.5Zn–0.3Mn alloy was prepared by metal mould casting method. Microstructure, aging behavior, mechanical properties and fracture morphology of the alloy were investigated. The results showed that α-Mg, Al11Nd3, Al2Nd and Mg32(Al,Zn)49 phases were the main phases of the as-cast alloy. And the long rod-like Al11Nd3 phase was decomposed to granular Al2Nd through T6 heat treatment. The tensile strength was also enhanced by T6 treatment. The yield strength was increased by 17% and 21% at RT and 150°C, respectively. It was mainly because that the precipitates were refined through T6 treatment and this became more benefit to hinder dislocations slipping. [Copyright &y& Elsevier]

Abstract: The mechanical properties of Ti-based metallic glasses prepared with different cooling rates have been carried out using nanoindentation at different loading rates. The effect of applied loading rate and sample size on the deformation was studied. It is found that lower loading rate promotes serrations or pop-in events. The gradual disappearance of pop-in events observed on load–displacement (P–h) curves represents a transition from discrete shear band activity at low loading rates to the simultaneous operation of multiple shear bands at higher loading rates. The pop-in size was observed to be load or contact depth dependent. An obvious creep displacement, sensitive to loading rates, was observed during the holding period at the maximum load. The cooling rate employed in sample preparation significantly influences the nano-mechanical properties of the metallic glasses, in that the ribbon sample exhibits lower hardness, incipient plasticity at lower applied load and greater pile-up height than bulk samples. [Copyright &y& Elsevier]