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The relative glass forming ability (GFA) of bulk amorphous Zr60Cu20Ni8Al7Hf3Ti2 (A1) and Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit105) alloys has been investigated by comparing the maximum thickness of amorphous region of wedge-shaped samples, as well as the evaluated critical cooling rates using differential thermal analysis (DTA). The results show that the maximum thickness of amorphous region of wedge-shaped samples are dm=2 mm for A1, dm=3.5 mm for Vit105, and the evaluated critical cooling rates are Rc=33.5 and 4.5 K/s for A1 and Vit105, respectively. It is suggested that the glass forming ability of A1 is smaller than that of well known Vit105 alloy, though A1 has the significant supercooled liquid region of over 140 K. Therefore, it is concluded that a large supercooled liquid region ΔTx does not necessarily mean good glass forming ability of an amorphous alloy. [Copyright &y& Elsevier]

This work systematically investigated the effect of Fe content on the microstructure and magnetic transition behaviors of melt-extracting Mn-Fe-P-Si microwires. It was shown that the Fe content does not change the main phase of the samples, i.e. Fe 2 P compound, which decreased with the increasement of Fe content. The transition temperature (T tran) decreased from 311 to 245.5 K while the thermal hysteresis (T hys) increased from 9.5 to 22.5 K increasing Fe from 0.90 to 1.05. The samples realized the first order magnetic transition at x = 1.00 and 1.05, correspondingly the samples demonstrated large magnetic hysteresis losses (W y ,) and isothermal magnetic entropy change (− ∆ S iso peak ) at 5 T, 59.1 J kg−1 and 14.5 J kg−1 K−1 for the sample x =1.00, 58.4 J kg−1 and 15.8 J kg−1 K−1 for the sample x = 1.05. In contrast, the samples at x = 0.90 and 0.95 indicated second order transition character, and the W y and − ∆ S iso peak were much smaller, i.e. 14.8 J kg−1 and 10.3 J kg−1 K−1, 9.7 J kg−1 and 10.7 J kg−1 K−1 respectively for the samples x = 0.90 and 0.95. The largest effective refrigerant capacity (RCE , 293.7 J kg−1, 5 T) is found at x = 0.90. The reduced hysteresis and maintained competitive isothermal magnetic entropy change make the melt-extracting Mn-Fe-P-Si microwires with optimized Fe content as a promising magnetocaloric material family applied in real magnetic refrigeration applications. [Display omitted] • The MnFe x P 0.5 Si 0.5 microwires were fabricated by melt-extracted method. • The amount of Fe 2 P main phase increased with the Fe content x decreasing. • The phase transition character corresponds to second order with the Fe content < 1. [ABSTRACT FROM AUTHOR]

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]

In this study, the deformation behaviors of a Cu 47.5 Zr 48 Al 4 Nb 0.5 bulk metallic glass composite (BMGC) in the temperature ranging from 663 K to 763 K have been investigated using uniaxial tensile tests and high-energy X-ray diffraction. Within the supercooled liquid region (SLR), the studied BMGC exhibits superplasticity and the deformation of the studied BMGC basically involves two modes, i.e., homogeneous and inhomogeneous deformation. As the temperature increases in the SLR, the yield strength of the studied BMGC gradually decreases whereas the plastic strain increases, revealing that the amorphous phase plays a dominant role in the deformation. However, there is a significant increase in the yield strength above the crystallization temperature, which indicates that the deformation is mainly contributed by the crystalline phase. The results obtained in this manuscript provide a better understanding of the temperature dependence of deformation behaviors in BMGCs. [Display omitted] • The yield strength of the BMGC decreases with the increasing temperatures below T x. • The structural evolution of the BMGC was characterized using high energy X-ray diffraction (HE-XRD). • The amorphous phase leads the deformation behaviors of the BMGC below T x , otherwise the crystalline phase dominates. [ABSTRACT FROM AUTHOR]

Here, the structure features of Cu 62 Zr 34.4 Al 3 Nb 0.6 amorphous alloy composites (AACs) are studied by combining experimental characterization with first-principles calculation. Element segregation, which is common in conventional alloy materials, does not occur in two phases (crystalline and amorphous phase) of the AACs due to complex solid solution. The lattice parameters, electron distribution, charge transfer and electrical potential, which are directly related to atomic bonding and lattice parameters of different structures, are obtained by calculating the various types of structural models, including interstitial solid solution, substitutional solid solution, B2 and amorphous phase. Finally, the formation and stability of solid solution in crystalline phase and amorphous phase are elucidated by first-principles calculation. The work has important guiding significance for understanding the two-phase structure and solidification mechanism in AACs materials. [Display omitted] • There is no obvious element segregation due to the complex solid solution structure. • The additional atoms into B2 phase causes the directional transfer of electrons. • The content and stability of two phases can be predicted by formation energy and single point energy. [ABSTRACT FROM AUTHOR]

Using electropulsing treatment (EPT), we proposed a method to effectively tune the free volume content and the mechanical performance of a Zr-based bulk metallic glass (BMG). No crystallization takes place but the atomic scale structure changes during EPT. Appropriate EPT parameter can facilitate the increase in the free volume content, thus tailoring the nanomechanical properties of the studied BMG. • Electropulsing treatment is employed to tune the structure and mechanical properties of a Zr-based bulk metallic glass. • Appropriate EPT parameter facilitates the increase in the free volume content. • The applied current density exerts a crucial role on the incipient plasticity. [ABSTRACT FROM AUTHOR]

Abstract Here, the compressive deformation behaviors of a CuZr-based bulk metallic glass composite (BMGC) has been studied under both unconfined and confined conditions. The threshold strain for the martensitic transformation (MT) is experimentally determined to be 0.8%, and 1.9% for the unconfined and confined compression, respectively. The complicated stress state in the confined compression postpones MT of the B2 phase, which has been verified by both experiments and molecular dynamic simulation. The yielding of the B2 phase is dominated by the uniaxial compressive stress. It is expected that the obtained results can provide more insights into the deformation mechanism of BMGCs. Graphical abstract Image 1 Highlights • The threshold strain for the martensitic transformation is quantitatively determined. • The complicated stress state in the confined compression postpones martensitic transformation. • The yielding of the B2 phase is dominated by the uniaxial compressive stress. [ABSTRACT FROM AUTHOR]

A novel type of bi-constituent wire composite was obtained by combining melt-extracted Gd 50 Al 30 Co 20 and Gd 55 Al 20 Co 25 microwire components with Curie temperature ( T C ) of 86 K and 110 K, respectively. For a field change of 5 T, the wire composite possesses a table-like feature spanning a temperature interval of 30 K with value of ∼8.6 J kg −1  K −1 , and enhanced refrigerant capacity (RC) and relative cooling power (RCP) values of ∼680 J kg −1 and ∼863 J kg −1 , respectively. The experimental results agree well with those calculated by a simple bi-composition model, demonstrating the possibility of designing wire-based composites with desirable magnetocaloric effects (MCE) for active magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Wire-arc additive manufacturing can fabricate components with complex geometries efficiently compared with other manufacturing methods. However, the uncontrolled grain size and tensile residual stress in as-fabricated components have limited their applications. In this study, laser shock peening, an innovative surface treatment technique, was specially-combined with wire-arc additive manufacturing to refine microstructure, modify stress state and enhance tensile properties of as-printed 2319 aluminum alloy. After peening, the average grain size decreased from 59.7 μm to 46.7 μm, and the percentage of grains with low angle boundaries increased from 34% to 70%. High density of dislocations and mechanical twins were generated and resulted in the increase of micro-hardness. Residual stresses were modified from tensile to compressive state with a maximum value around 100 MPa. Yield strength was remarkably increased by 72%. This combined printing and peening manufacturing strategy provides microstructure and quality control of manufactured components for practical applications. [ABSTRACT FROM AUTHOR]

As important aeronautics and astronautics materials, the Al-Zn-Mg-Cu alloys have been fabricated by spray deposition. The effects of Mg and Cu on the microstructures and mechanical properties were systematically investigated. The S (Al 2 MgCu) and θ (Al 2 Cu) phases exist in equilibrium solidification conditions, but they were not found in the rapid solidification conditions due to the change of solidification paths and phase components during the spray deposition process. The volume fraction of the secondary phases/precipitates increases with increasing Mg content, which leads to the improvement of yield strength as well as to raise tendency of intergranular fracture. Undissolved phases can be promoted by increasing Cu content in the Mg-rich (∼2.65 wt% Mg) alloys. Furthermore, Cu has weak effects on yield strength but plays a positive role in maintaining the peak strength value of the alloys in overaged condition. The alloy with a medium (Mg+Cu) content shows superior overall properties: the ultimate tensile strength (UTS), yield strength (YS) and elongation can reach values of 812 ± 3 MPa, 780 ± 3 MPa and 7.0 ± 0.7%, respectively. [ABSTRACT FROM AUTHOR]

Emerging high-entropy alloys (HEAs) exhibit high strength, high ductility and high toughness relative to traditional alloys based on one or two principal elements. The superior mechanical properties are derived from a synergy of multiple deformation mechanisms and their interactions at different stages of plastic straining. It is thus important to uncover the activation and operation of deformation mechanisms in these materials for property optimization and potential structure applications. The present work carried out in-situ tensile deformation of a CrMnFeCoNi HEA at room temperature. The strain hardening rate did not change monotonically during tensile deformation. Surface morphology evolution revealed the effects of massive dislocation activity, activation of multiple slip bands and their interactions on the strain hardening rate. Crack-tip-opening-angle measurements show that the current alloy possesses high fracture toughness. Cracks initiated at dense slip zones and grain boundaries, and propagated gradually, eventually coalescing into main cracks and resulting in final fracture. • The fracture toughness of CrMnFeCoNi HEA was evaluated by the CTOA and the steady-state CTOA was about 20°. • The evolution of the slip bands during tensile deformation was characterized using a series of in-situ experiments. • The relationship between the changes of SHR and surface morphologies of CrMnFeCoNi HEA was established. [ABSTRACT FROM AUTHOR]

Very recently, we reported that Fe-doped Ni 50-x Fe x Mn 38.0 Sn 12.0 alloys exhibited enhanced magnetization difference Δ M between the martensite and austenite phases. Of note is that the alloy with x = 4.2 exhibits a strong metamagnetic transition behavior, i.e. magnetic-field-induced reverse martensite transformation, which is favorable for the magnetocaloric effects. Here, the enhanced magnetocaloric effect related to metamagnetic transition in the selected Ni 35.8 Fe 4.2 Mn 38.0 Sn 12.0 alloy was reported. This alloy exhibits a high magnetization difference Δ M of ∼58 A·m 2 /kg between martensite and austenite phases owing to the magnetic and structural coupling. The doping of Fe leads to a strong metamagnetic behavior, with austenite peak temperature shift Δ A p / Δ H reaching −2.4 K/T. As a result, the magnetic entropy change Δ S m increases rapidly from a starting critical magnetic field ∼0.2 T and then saturates at various finishing critical magnetic fields, depending on the working temperature. A sizable peak Δ S m of 33.8 J/kg·K with a working temperature interval of 7 K is obtained under a magnetic field of 5 T, which is responsible for a high relative cooling power RCP of 237 J/kg. These results suggest that Ni 45.8 Fe 4.2 Mn 38.0 Sn 12.0 alloy may act as a potential solid-state magnetic refrigerant. [ABSTRACT FROM AUTHOR]

We report enhancements of both Curie temperature and magnetic refrigerant capacity in Gd 50 (Co 69.25 Fe 4.25 Si 13 B 13.5 ) 50 microwires, which were fabricated by the melt-extraction method. For a field change of 5 T, the maximum magnetic entropy change (−Δ S M max ), the refrigerant capacity (RC) and relative cooling power (RCP) reached high values of 6.56 J kg −1 K −1 , 625 J kg −1 and 826 J kg −1 , respectively. While the RC is similar to those of our previously reported GdAlCo microwires, a much broader working temperature range of ∼126 K and a higher Curie temperature of 170 K make the Gd 50 (Co 69.25 Fe 4.25 Si 13 B 13.5 ) 50 microwires more attractive for active magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In this work, the effect of Sc content on the microstructures and mechanical properties of Al-Zn-Mg-Cu-Zr alloys prepared using spray deposition was studied. Microstructure observations reveal that not only the grain size, but also the coarse secondary phase can be refined by Sc addition through the formation of a hybrid structure coupled by η-MgZn 2 and Al 3 (Sc, Zr) phases near and at the grain boundaries. It is inferred that the primary Al 3 (Sc, Zr) particles can act as nucleation sites for the η-MgZn 2 phase during the deposition process. With the increase of Sc content, the continuous secondary phase at the grain boundaries converts gradually into small discontinuous particles, which contributes to the considerable improvement in tensile strength and elongation. The alloy with 0.2 wt% Sc exhibits excellent combinations of ultimate tensile strength of 831±3 MPa and elongation of 10.2 ± 0.4% after T6 heat treatment, and the elongation increases by almost 50% compared to the Sc-free base alloy. [ABSTRACT FROM AUTHOR]

Ni-Mn-Sn alloys exhibit high magnetocaloric effect (MCE) during the magnetic-field-induced martensite to austenite phase transformation. However, the low magnetization of the austenite, narrow working temperature interval and high magnetic hysteresis reduced their magnetic refrigeration capacity. Here, the effects of Fe doping on the structural and magnetic transitions of Ni 50-x Fe x Mn 38 Sn 12 alloys were investigated. The doping of Fe higher than 2.9% induced the occurrence of a secondary γ phase, creating a dual phase alloy. The martensite transformation temperature significantly decreased with the occurrence of the secondary phase. However, the Curie temperatures of both austenite and martensite changed slightly with the formation of the secondary phase. As a result, the magnetostructural coupling, i.e. overlap of the structural and magnetic transitions between the ferromagnetic austenite and the paramagnetic martensite, occurred in the alloys with x = 0.5 - ∼4.2. Furthermore, the magnetization of the austenite and martensite both increased with increasing Fe content from x = 0 to x = 5.5, with the magnetization difference between the austenite and martensite saturating at x = 4.2. The dual phase Ni 45.8 Fe 4.2 Mn 38 Sn 12 alloy, exhibiting a magnetic field dependence of martensite transformation temperature ΔT M / μΔH - 0.28 K/kOe, showed a wider working temperature interval than that of the un-doped Ni 50 Mn 38 Sn 12 alloy. This demonstrated that the Ni 45.8 Fe 4.2 Mn 38 Sn 12 alloy might exhibit a high magnetic entropy change, wide working temperature interval and low magnetic hysteresis, and thus may be a promising magnetic refrigeration material. [ABSTRACT FROM AUTHOR]

Commercial low temperature Sn-based solders including Sn In eutectic solder show non-wetting on Zr 55 Cu 30 Al 10 Ni 5 metallic glass (BMG) directly in vacuum sessile drop experiments. The results mean that wetting completely on Zr-based BMGs by adjusting composition of Sn-based solders would fail usually. By utilizing pitting corrosion sensitivity of chloride of Zr-based BMGs, liquid Sn displays a slow wetting and spreading processes of experimental time window on Zr 55 Cu 30 Al 10 Ni 5 BMG surfaces, which are pretreated by molten ZnCl 2 . Six BMG specimens, which are treated in the same way by melting ZnCl 2 , show different final contact angles by Sn. The different roughness morphology of the BMG surface, which is caused by molten ZnCl 2 , determines the different final contact angles of Sn. The driving force is caused by liquid Sn nucleation at the interface on modified BMG surfaces, which determines the final contact angle and the time of the spreading process to equilibrium states. [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]

High magnetic entropy change and wide working temperature interval are both of great importance for the application of magnetic refrigerant working materials. Here Ni–Mn–In–Co alloys with oligocrystalline structure were produced by annealing heat treatment and the giant magnetocaloric effect and large working temperature interval were confirmed. The annealing increases the magnetization difference ΔM between martensite and austenite. The annealed alloy subjects to a reverse martensite to austenite and an intermediate phase transformation upon heating. The two-stage field-induced reverse transformation, contribute to a maximum magnetic entropy change of 37.1 J/kgK at 309 K under a magnetic field of 50000 Oe, were observed for the first time. In addition, a broadened working temperature interval of ∼22 K was obtained owing to the intermediate phase transformation. The giant room-temperature MCE in quaternary Ni–Mn–In–Co alloys is promising for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The growth kinetics of the diffusion layer between molten Sn and Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass (BMG) substrate were examined by isothermal aging at the temperature range between 513 and 633 K with 30 K temperature interval. The aged samples were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The growth of the diffusion layer is mainly controlled by a diffusion-controlled mechanism over the temperature range at stage I, and the value of the time exponent is approximately 1/2 by fitting the experiment data. As well as there is unusual stage II, whose time exponent of the growth is suppressed to 1/3. Based on phenomenological description, it could deduced that phase transition such like nucleation and coalescence occur in vicinity of the interface of diffusion layer at the late stage of clusters growth processes similar to Ostwald ripening. [ABSTRACT FROM AUTHOR]

The isothermal relaxation kinetics equations of free volume was derived based on the defect relaxation kinetics expressions. The equations were used to fit the isothermal thermal analysis curves of Al 85 Ni 8 Y 5 Co 2 amorphous alloy at different temperature and giving out several crucial parameters associated with the structure relaxation kinetics and metastable structure for example the kinetic coefficient and the fragile strength coefficient. The fitted parameters indicate excellent consistence with the previously reported data, manifesting isothermal thermal analysis based on the kinetics equations presented in this paper is applicable to investigate the metastable structure and structure relaxation of amorphous alloys, providing a novel method more convenient than the traditional viscosity monitoring method. [ABSTRACT FROM AUTHOR]

Herein, we reported the influences of accumulated direct current annealing (ADA) on the GMI properties and microstructures of Zr-doped melt-extracted (Co 68.15 Fe 4.35 Si 12.25 B 12.25 Zr 3 ) amorphous microwires. There indicated that ADA-ed wires enhanced GMI properties and improved the microstructures remarkably in comparison with as-fabricated wires. The maximum GMI ratio [Δ Z / Z 0 ] max and equivalent magnetic circumferential anisotropy field (EMCAF) of ADA-ed microwires were increased to 256.01% and 4 Oe at 20 MHz, respectively, which are more than nearly 8 and 2 times of 33.62% and 1.6 Oe for as-fabricated wires, respectively. Moreover, the maximum magnetic field response sensitivity ( ξ max ) increased to 372.57%/Oe, which is much higher than the as-fabricated wires of 44.71%/Oe. The remarkable enhancement of GMI performance was considered as the microstructural evolution including structural relaxation, appearance of nano-crystallization, and circumferential arrangement of surface magnetic domains. Nano-crystallization degree and circumferential magnetic domains arrangement were effectively improved by actions of Joule thermal energy and circular magnetic field generated ADA as shown in HRTEM and magnetic force microscope (MFM) analysis. Based on above, both the excellent GMI performances and relatively large ξ max values indicate the ADA is an effective annealing technique for thermal treating the melt-extracted amorphous wires which applied for potentially magnetic sensor in detecting low-intensity magnetic fields. [ABSTRACT FROM AUTHOR]

Annealing treatment below the glass transition temperature of Zr 55 Cu 30 Al 10 Ni 5 bulk metallic glass (BMG) specimens are investigated. Every 10 K temperature interval isothermal limited annealing treatment time will be selected to draw up time–temperature–transformation ( T – T – T ) curve. The apparent activation energy of crystallization is about 325 ± 7 kJ/mol, higher than the values of supercooled liquid region conditions. Surface hardness of the samples before and after the limited annealing treatment are tested by nanoindentation, where the spherical-like crystallization morphology indicate the higher standard deviation of surface hardness of the BMG after the limited annealing treatment. The crystallization kinetics of the Avrami exponent is 4 in accordance with spherical-like crystallization morphology. A short review on mathematical setting of the problem could distinctly give the differences of the different crystallization behaviors at different temperature regions. Avrami exponent is from 4 to 3, explaining the crystallization morphology is from spherical-like to dendritic, could be ascribed to the concepts of symmetry breaking. [ABSTRACT FROM AUTHOR]

We reported the magnetocaloric properties of Heusler-type Ni 48 Mn 26 Ga 19.5 Fe 6.5 microwires with diameter of ∼50 μm which were fabricated by a precise melt-extraction method. The Fe-doped Ni–Mn–Ga microwires after chemical ordering heat-treatment exhibit negligible thermal and magnetic hysteresis along the axial direction due to their small magnetocrystalline anisotropy and display excellent magnetocaloric effect (MCE) for both magnetic (paramagnetic–ferromagnetic) phase transition and structural (austenite–martensite) phase transition. The maximum entropy change (−Δ S m ), ∼4.7 J kg −1 K −1 , is obtained during the structural transition induced by an external magnetic field of 50 kOe at a temperature of ∼361 K. Moreover, tiny positive magnetic entropy also appears when the applied field is lower than 5 kOe. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effect of structural relaxation on the nano-mechanical behaviors of BMGs is studied. [•] The indent load at first pop-in event, the hardness and Young’s modulus are enhanced after annealing. [•] The differences in nanomechanical properties can be attributed to their different atomic structure. [Copyright &y& Elsevier]

• All melt-extracted Cu 45 Zr 45 Co 10 amorphous alloy microwires fracture by shear cracking. • A positive rate-sensitivity of fracture strengths was discovered in microwires. • Increasing strain rates incurs the decrease of fracture reliability. • The fracture reliability is dominated by a square root singularity of the characteristic shear offset lengths. The understanding of the fracture mechanism of amorphous alloys (AAs) is of importance for their engineering applications as advanced structural materials. In this study, a series of micro-tensions of Cu 45 Zr 45 Co 10 AA microwires were conducted under different strain rates ranging from 5 × 10−5 s−1 to 1 × 10−2 s−1. It is found that all microwires fracture by shear cracking, but the shear fracture strengths exhibit pronounced rate-dependent uncertainties. Based on both lognormal and Weibull statistical analyses, the studied AA microwires reveal a positive rate-sensitivity of fracture strengths. However, increasing strain rates incurs the decrease in the fracture reliability. We demonstrate that the fracture reliability of AA microwires is dominated by a square root singularity of the characteristic lengths of shear offset on fracture surfaces, which satisfies linear elastic fracture mechanics. [ABSTRACT FROM AUTHOR]

Highlights: [•] High-quality Gd55Al25Co20 metallic glass magnetocalorific fibers were melt-extracted. [•] They show superior MCE performance versus its counterpart in BMGs. [•] They have tensile strength of 1189MPa and high security threshold of 796MPa. [•] The excellent performances result from size effect and amorphous structure. [Copyright &y& Elsevier]

• The relationship between the relative clearance and the fractured morphologies of the punched-out HEA was established. • The fractured surfaces of punched-out disc are composed generally of deformation zone, fracture zone, and burr zone. • The relative clearance affects the distribution of stress states of HEA plate during shear punching process. In this paper, the deformation and fracture behaviors of Co 20 Cr 20 Fe 20 Ni 20 Mn 15 Cu 5 high entropy alloy plates in the shear punching tests were studied. The fractured surfaces of the punched-out high entropy alloy discs consist of three parts, i.e., the deformation zone, the fracture zone, and the burr zone. As the ratio of clearance to the plate thickness, i.e., the relative clearance, gradually increases, the percentages of both deformation zone height and burr zone height increase. This phenomenon was attributed to the changes of stress states during shear punching process. Meanwhile, a larger relative clearance favors more plastic deformation, generating numerous slip bands and some elongated dimples on the fractured surface. [ABSTRACT FROM AUTHOR]

Abstract: In order to clarify the competing relationships among the intermetallic precipitation phases during the cooling of a bulk amorphous Zr56.6Cu17.3Ni12.5Al9.6Ti4 alloy, the wedge-shaped ingots of this alloy were made by casting the melt into a wedge-shaped copper mould, and then the zones with different cross-sections were studied by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that these phases are very different in both the morphology and sizes, and they are dependent on the thickness of wedge ingot, i.e., the cooling rates. It is therefore concluded that the Zr2Ni phase is the strongest competing rival to the amorphous matrix in this alloy. These findings support that compared to Zr–Ni pair, Zr–Cu pair has a larger glass forming tendency. The glass forming ability can be improved by inhibiting the precipitation of Zr2Ni phase by, for example, decreasing the Ni content in this alloy. [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]

Abstract: X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and differential scanning calorimetry (DSC) were performed to investigate the critical cooling rate and thermal stability of Ti40Zr25Ni3Cu12Be20 metallic glass. The critical cooling rate for glass formation of the studied metallic glass is determined to be as low as 3.2K/s, revealing a high glass-forming ability. The activation energies of the alloy are strongly dependent on the cooling rate during rapid solidification. Compared with the ribbon sample, the bulk sample that experiences slower cooling rate during solidification contains a greater degree of medium range orders (MRO), which favors nucleation, therefore leading to its smaller activation energies. [Copyright &y& Elsevier]

Abstract: New bulk metallic glasses are produced by substituting a few atomic percentages of iron with yttrium in the Fe45−x Cr16Mo16C18B5Y x (x =0, 1, 2, 3) alloy systems. The study shows that the optimum yttrium content in the alloy for the best glass-forming ability is 2at.%, and with this composition fully amorphous as-cast samples with a size of 6mm in diameter can be produced by the copper mold casting. The mechanism for the effect of yttrium addition on the glass-forming ability of the Fe45−x Cr16Mo16C18B5Y x (x =0, 1, 2, 3) alloys is discussed according to the effect of yttrium content in the alloy on the characteristic temperature values as measured by using DTA in this study. Furthermore, the compression tests of the bulk amorphous samples of Fe43Cr16Mo16C18B5Y2 alloy show that the room temperature compressive strength of the amorphous alloy is approximately 1824MPa. [Copyright &y& Elsevier]

• CrMnFeCoNi HEA exhibits excellent mechanical properties at cryogenic temperatures. • Enhanced yield strength of the alloy stems from the larger lattice distortion. • High dislocation density and nano-twins lead to the high SHR. • Lower deformation temperature pronouncedly decreased SFE. Here, the evolution of the deformation mechanism of the well-known CrMnFeCoNi high entropy alloy (HEA) under a cryogenic temperature was investigated via using transmission electron microscopy characterization after compressive experiments. It is found that, in contrast to the dominate mechanism of dislocation slip at 298 K, the deformation mode of the studied HEA at 123 K can be divided into two stages: (i) at the initial plastic stage, the plasticity is mainly induced by the planar dislocation glide; and (ii) at the late plastic stage, the combination of dislocation hardening and mechanical twinning facilitates high strength for the studied alloy. These findings are helpful to understand the temperature dependent deformation mechanism of high entropy alloys. [ABSTRACT FROM AUTHOR]

• The cooling induced structural evolution of CuZr-based BMGC is in-situ studied. • The hydrostatic pressure exerts a crucial role on the martensitic transformation of B2 CuZr phase. • The thermodynamics mechanism of the phase transformation of CuZr phase is clarified. [Display omitted] In - situ high-energy X-ray diffraction and molecular dynamic simulation were employed to study the structural evolution of a B2 phase reinforced CuZr-based bulk metallic glass composite in different structural states during cryogenic treatment between 300 K and 100 K. No phase transformation occurs in the as-cast sample during cryogenic treatment, while the pre-strained sample undergoes martensitic transformation and reverse martensitic transformation. The ambient temperature, uniaxial stress, and hydrostatic pressure on the B2 CuZr phase are closely related to the phase transformation behavior of the CuZr phase in the pre-strained composite sample. Molecular dynamic simulation confirms the experimental results. The findings in this work will help to clarify the mechanism of the martensitic transformation in the B2 CuZr phase, and finely tune the structure and mechanical behaviors of CuZr-based bulk metallic glass composites. [ABSTRACT FROM AUTHOR]

In this study, the effect of cryogenic testing temperatures on the deformation behavior of a CuZr-based bulk metallic glass composite (BMGC) has been investigated using in situ high energy X-ray diffraction. The yield strength and work-hardenability of the studied BMGC show an increasing trend from 298 K to 153 K. A higher yield strength at a lower temperature can be attributed to the larger difference in the volume shrinkage between the crystalline phase and the amorphous matrix. The increasing martensitic transformation degree of the crystalline phase from 298 K to 153 K results in the enhanced work-hardenability. These results lead to a better understanding of the temperature dependence of phase-transformation induced plasticity in CuZr-based BMGCs. ga1 • The yield strength of the BMGC shows an increasing trend from 298 K to 153 K. • The increase of the work-hardenability is attributed to martensitic transformation. • Martensitic transformation degree is higher at a lower temperature. [ABSTRACT FROM AUTHOR]

The effects of trace Fe-doping on the magnetic and magnetocaloric performances of Gd-based metallic microfibers were systematically and detailedly investigated in this article. Experimental results indicated that the Gd-based microfibers prepared by the rotated-dipping process are uniform and continuous, with typically amorphous structure characteristics and favorable thermal stability. Curie temperature T C of Gd-based amorphous microfibers increases with the rising of Fe content, and the T C of GdAlCoFe3 microfibers is the highest at 128.7 K (relatively increased by 15.3 K than before doping). Among the general magnetic performance indicators, the saturation magnetization M s of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g. Furthermore, the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping amount. When the external magnetic field H ex = 50,000 Oe, the maximum magnetic entropy change -Δ S m max, refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K, 748.22 J/kg and 1006.90 J/kg, which increased by 0.07 times, 0.13 times and 0.16 times, respectively than before Fe-doping (namely -Δ S m max = 9.68 J/kg·K, RC = 663.79 J/kg, RCP = 871.73 J/kg). From the perspective of microstructural changes, Fe-doping results in the formation tendency of atomic clusters and nanocrystals in micro-regions, the orderly orientation of atoms appears, and the magnetic anisotropy increases accordingly. In addition, the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy, which in turn leads to an increase in Curie temperature and an improvement in magnetocaloric performance. Since RC and RCP are the main indicators in engineering applications, the GdAlCoFe1 amorphous microfibers can be selected as a low-temperature magnetic refrigeration working medium to provide technical guarantee for the application of magnetic refrigeration technology. In comparison to Fe-doped Gd-based amorphous microfibers, # GdAlCoFe1 microfibers have enhanced magnetocaloric properties by coactions of atomic arrangement ordering transformation (AAOT) and magnetic moment ordering transformation (MMOT). Image 1 • Influence of Fe-doping amounts on the magnetocaloric properties was investigated systematically. • MCE properties of # GdAlCoFe1 amorphous fibers were enhanced effectively. • Interaction mechanism was illustrated from the perspective of atomic arrangement and magnetic moment ordering transformation. [ABSTRACT FROM AUTHOR]

We report upon the excellent magnetocaloric effect in melt-extracted DyHoCo medium entropy microwires. The magnetic entropy change (-Δ S M) reaches a large value of ∼11.2 J kg−1 K−1 for a field change (μ 0 Δ H) of 5 T. The large value of -Δ S M is resulted from the large magnetic moments of Dy and Ho. In addition, the DyHoCo microwires show a good cooling efficiency; RC1, RC2 and RC3 are evaluated to be ∼530 J kg−1, ∼417 J kg−1 and ∼279 J kg−1, respectively, at μ 0 Δ H = 5 T. The DyHoCo microwires undergo a second-order paramagnetic-ferromagnetic transition at the Curie temperature of ∼35 K. The excellent magnetocaloric property makes the melt-extracted DyHoCo microwires a promising refrigerant for cryogenic cooling application. Image 1 • Dy 33.3 Ho 33.3 Co 33.4 medium entropy microwires were fabricated by melt-extraction. • DyHoCo microwires possess an amorphous structure and SOMT. • DyHoCo microwires show the excellent MCE performance. [ABSTRACT FROM AUTHOR]

In this work, a long-term room-temperature aging treatment of the order of years is applied to a B2 phase-reinforced CuZr-based bulk metallic glass composite (BMGC). Presumably governed by residual stress, B19' CuZr martensitic phase gradually precipitates in the crystals after such long-term aging, while structural relaxation takes place in the glassy matrix, which finally induces precipitation of Cu 10 Zr 7 nanocrystals. Tensile tests prove that these time-dependent structural changes have a measurable effect on deformation behaviors of BMGC. The findings are helpful for understanding the thermodynamic stability and the kinetics of structural evolution of metastable alloys and have useful implications for tailoring the structure and mechanical behavior of BMGCs. Image 1 • Natural aging induces structure evolution in CuZr-based bulk metallic glass composite. • Structure stabilization occurs in both the B2 CuZr phase and the amorphous phase. • Hydrostatic pressure plays a crucial role in the structural transformation of phases. [ABSTRACT FROM AUTHOR]

This study deals with the densification of a pre-alloyed TiAl powder with excessive yttrium addition by spark plasma sintering (SPS) technique. The gas-atomized Ti–43Al–5Nb–2V–1Y (at. %) powders were sintered at various temperatures between 1100 and 1250 °C, applying a uniaxial pressure of 40 MPa. The microstructures of pre-alloyed powders and SPSed TiAl alloy samples were analyzed by scanning and transmission electron microscopies. In addition, the compression tests of SPSed alloys was carried out at room temperature (RT). Attention is focused on the existing form and distribution of excess yttrium in the initial powders and the SPSed samples. The initial powder exhibits a dendrite structure, and yttrium-rich phases (YAl 2) are segregated along the interdendritic zone. After sintering, duplex, nearly lamellar (NL) and fully lamellar (FL) microstructures were obtained as a function of the sintering temperature. For duplex and NL microstructures, the YAl 2 phases are fine granular precipitates in homogeneous dispersion state. Conversely, stripe-like YAl 2 precipitates, which surround the α 2 /γ lamellar colonies, emerged in the FL microstructures. Excessive sintering temperature leads to grain growth and serious segregation of the YAl 2 phases, and it deteriorates the mechanical properties of this alloy eventually. Image 1 • TiAl alloy with excessive yttrium addition was prepared by spark plasma sintering. • Fine YAl 2 particles are dispersed in samples sintered at relatively low temperature. • Strip-like YAl 2 phases with network structure formed in FL microstructure. • The SPSed alloys with fine YAl 2 particles own better compression properties. [ABSTRACT FROM AUTHOR]

The enhanced magnetocaloric properties are studied in melt-extracted Gd 36 Tb 20 Co 20 Al 24 metallic glass microwires. The Curie temperature is ∼91 K for these microwires which show promising applications at liquid nitrogen range. The microwires possess spin glass phase in low temperature and spin freezing temperature is 60 K. Notably, the maximum magnetic entropy change (–Δ S M max), the relative cooling power (RCP) and the refrigerant capacity (RC) reach high values of 12.36 J kg−1K−1, 948 J kg−1 and 731 J kg−1, respectively, under a field change of 5 T. The large –Δ S M max originates from the high effective magnetic moment. Meanwhile, the spin fluctuation, the exchange integral fluctuation of metallic glass and the second order paramagnetic-ferromagnetic transition enlarge the phase transition range. Image 1 • Gd 36 Tb 20 Co 20 Al 24 metallic glass microwires were prepared by melt-extracted method. • The microwires show the maximum magnetic entropy change of 12.36 J. kg−1K−1. • The microwires exhibit refrigerant capacity of 731 J. kg−1. [ABSTRACT FROM AUTHOR]

Abstract: Compressive deformation behaviors of a cast Ti40Zr25Ni3Cu12Be20 bulk metallic glass in the test temperatures ranging from 428 to 658K were examined in a broad range of strain rates from 1.3×10−4 to 3×10−2 s−1. The alloy studied exhibits an extraordinary compressive superplastic formability within the supercooled liquid region, typically evidenced by a large compressive strain up to 0.83. The superplastic flow behaviors are strongly dependent on the test temperatures and applied strain rates. At low temperatures or high strain rates, the viscosity measured is found to dramatically decrease with increasing strain rate (i.e., non-Newtonian flow) and a stress overshoot is detected in the first steps of strain. At low strain rates or high test temperatures, the studied glass exhibits a Newtonian flow behavior. The value of activation volume increases with increasing test temperatures. [ABSTRACT FROM AUTHOR]