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Four drying methods, hot air drying (HAD), microwave constant temperature drying (MWD), microwave vacuum temperature‐controlled drying (MIVD‐T50), and freeze drying (FD), were investigated for their effects on raspberries in terms of drying time, color, microstructure, rehydration, water activity, phenolic compounds, flavonoids, anthocyanins, and DPPH scavenging ability. It was found that microwaves combined with vacuum took the shortest time. The color of MIVD‐T50 is similar to that of FD and much better than that of HAD and MWD. A smooth surface and fluffy and porous structure inside were observed in the FD and MIVD by scanning electron microscopy (SEM) images. FD has the highest energy consumption, followed by HAD, MIVD‐T50 and MWD. The retention rates of total phenols and flavonoids in HAD, MWD and FD were lower than those in MIVD‐T50, and FD had the advantage of retaining anthocyanin content. In general, MIVD‐T50 has significance for the commercial production of raspberry. Practical applications: The use of natural antioxidants in food processing not only enhances the shelf life of products but also improves their nutritional value. Raspberry is a rich source of antioxidants and is widely used in food processing. However, the drying process is crucial in preserving its antioxidant quality, and different drying methods affect the antioxidant content differently. According to the results of the experiments, the drying method has a considerable impact on the energy usage and quality of dried raspberries. Compared with the HAD and MWD treatments, both FD and MIVD‐T50 showed better nutrient content preservation and antioxidant activity, which may be caused by the lower temperature drying process of FD or the stronger efficiency of MIVD‐T50. However, the drying time of FD is longer, and the energy consumption is higher. Therefore, MIVD‐T50 is a promising raspberry drying technology with low energy consumption, a short drying time, and high quality. It has huge development potential and broad commercial scale production market prospects. [ABSTRACT FROM AUTHOR]

To further determine the brittle-to-ductile transition temperature, the microstructures and mechanical properties of typical forged β-solidifying Ti-42Al-5Mn (TiAlMn) and Ti-43Al-4Nb-1Mo-0.5B (TNM) alloys were studied. The results show that the microstructures of both heat-treated alloys consist of γ/α2 lamellar colony, equiaxed γ phase, and β0 phase. In addition, the globular α2 phase appears in the TNM alloy. The yield strength of TiAlMn alloy increases gradually with the testing temperature, whereas a significant drop from 605 MPa to 469 MPa occurs between 650 °C and 700 °C. In contrast, the TNM alloy exhibits a declining trend with the increasing testing temperature, and a remarkable reduction is observed in the temperature range of 700 °C–750 °C. Moreover, the fracture mode transition from transcrystalline cleavage to intercrystalline with increasing testing temperature was applied to the auxiliary judgment of brittle-to-ductile transition. As a result, the brittle-to-ductile transition temperatures of TiAlMn alloy and TNM alloy are about 650 °C–700 °C and 700 °C–750 °C, which may provide a reference for service temperature range of both alloys. [ABSTRACT FROM AUTHOR]

The mechanical responses of hexagonal close-packed (HCP) materials are highly anisotropic, as well as strain rate and temperature-dependent, because of inherently asymmetric slip and twinning in constituent crystalline grains. How slip and twinning are affected by strain rate/temperature and how they alter the deformation response of HCP materials are still not well understood. To provide greater insights, a novel crystal plasticity model is proposed to describe the mechanical behavior and microstructure evolution of single-crystal and polycrystalline HCP materials under different loading conditions. A new flow rule is developed, which incorporates the effects of strain rate and temperature on the activation of specific deformation mechanisms. Both dislocation density-based and empirical hardening laws are adopted to describe the overall hardening contributed by slip, twinning, and their interaction, taking into consideration loading conditions and the difference between tension and compression twinning. The proposed model is implemented in the commercial FE package ABAQUS via a user-defined subroutine. The mechanical response and microstructure evolution of single-crystal titanium with different orientations, and polycrystalline titanium comprising grains with 350 random orientations, subjected to deformation at different strain rates and temperatures, are numerically explored. The numerical results display good agreement with published experimental data. The simulations indicate that an increase in strain rate or decrease in temperature will retard the activation of slip systems, thereby promoting twinning instead. A higher twinning volume fraction leads to a larger amount of lattice reorientation, more pronounced hardening, and higher stress levels. This effort has yielded a greater understanding of the influence of strain rate and temperature on the mechanical response of HCP materials and facilitated mesoscale simulations that couple slip and twinning. • A novel flow rule considering the effect of strain-rate and temperature is proposed. • Tensile twinning and compressive twinning are distinguished in calculations. • Different hardening laws are used to take strain rate and temperature into account. • The macroscale and mesoscale deformation behaviors of α -Ti are investigated. [ABSTRACT FROM AUTHOR]

In situ SEM experimental system is employed to investigate the mechanical characteristics and the fracture behavior of 91W-6.3Ni-2.7Fe tungsten alloys. The crack initiation and propagation of tungsten alloys under tensile loadings are examined. Multi-particle unit cell models containing the microstructure characteristics of tungsten alloys are established. Fixed-point iteration method is firstly used for the multi-particle unit cell's boundary condition. By adopting the method, real displacement constrained conditions are applied on the multi-particle unit cell models. The mechanical and fracture behaviors of tungsten alloys under tensile loading are simulated. The effects of tungsten content, particle shape, particle size, and interface strength on the mechanical properties of tungsten alloys are analyzed. The relationship between the mechanical behaviors and the microstructure parameters is studied. A good agreement is obtained between the experimental results and the numerical predictions, verifying the rationality of the FE models using the fixed-point iteration method. [ABSTRACT FROM AUTHOR]

• Confining pressure effect on dynamical mechanical properties of cemented tailings backfill (CTB) was investigated. • Increasing the average strain rate (ASR) led to a remarkable increase in CTB's dynamic peak compressive strength (DPCS) under confining pressure. • The fitting equations were developed to forecast the relationship between impact amplitude and DPCS under confining pressure. • Microstructural characteristics of CTB after SHPB test with confining pressure were obtained through CT techniques. This paper discusses the relationship between the average strain rate (ASR), confining pressure, dynamic peak compressive strength (DPCS), and cemented tailings backfill (CTB) crack volume through the SHPB test and microscopic computed tomography (CT). The CTB samples with a water-cement ratio of 1:4 and a slurry concentration of 75% were prepared to carry out SHPB tests with different ASR (25.6 ∼ 104.73 s−1), different ASR (12.16 ∼ 152.05 s−1) at different confining pressures (0.5 ∼ 2 MPa). The results show that with the increase of ASR when there is no confining pressure, the DPCS shows a trend of first increasing and then decreasing. However, when the confining pressure is 0.5 and 1 MPa, the DPCS increases linearly. When the confining pressure is 1.5 and 2 MPa, the DPCS increases exponentially and logarithmically, respectively. The micro-CT analysis shows that the total crack volume generated after the SHPB rises first and then falls with the increase of the ASR under confining pressure of 1 MPa. When the impact amplitude is 150 mV, the crack volume also decreases with the improvement of the confining pressure (0.5–2 MPa). The internal cracks of the CTB change from shear cracks to tensile cracks, and the initial pores of the samples first decrease and then increase. The failure pattern of all CTB samples by SHPB was mainly shear, tensile, and hybrid failure (shear and tensile). The research results can provide a valuable reference for the dynamic performance of CTB under confining pressure and the design of mining backfill. [ABSTRACT FROM AUTHOR]

• The atomic Voronoi volume of the grain interfaces is larger than that of the grain interiors, owing to the lack of <0,0,12,0> and <0,1,10,2> clusters. • The gradient microstructure changes the shock characteristics of shear strain, stress, and temperature in the nanoglasses. • Unlike traditional polycrystalline, the effect of gradient microstructure on the shock wave speeds of nanoglasses is weak, so the indirect method of estimating the spall strength is still applicable to the gradient nanoglasses. • The utilization of a negative gradient structure effectively increases the spall strength of nanoglasses. Shock is one of the physical processes that materials are most likely to suffer during applications, therefore the elusive shock properties of nanoglasses are unacceptable. Additionally, establishing gradient microstructure is a promising approach to optimize mechanics properties further. Here, shock characteristics of Cu 64 Zr 36 nanoglasses with gradient microstructures are systematically investigated by molecular dynamics simulations in the particle velocity range of 0.5 to 5 km/s. Two types of gradient nanoglasses (GNGs) along the shock direction are prepared and analyzed, i.e., a negative gradient structure (S1) in contrast with a positive gradient structure (S2). The results show that the number of mechanically stable <0,0,12,0> and <0,1,10,2> atomic Voronoi polyhedra, which are typical building blocks of the amorphous structure in terms of Voronoi tessellation method, in grain interfaces is significantly less than that in grain interiors. As a result, the local free volume gradually changes along the shock direction by the designed gradient structure, which causes a significant impact on the shock wave profiles of shear strain, stress, configurational entropy, and temperature in the GNGs. However, due to a similar chemically-disordered feature in grain interiors and interfaces, the shock wave speeds of nanoglasses are not sensitive to grain sizes under the same shock strength, contrary to the usual shock wave speed mechanism in conventional polycrystalline. Thus, unlike traditional polycrystalline with grain size gradient, the indirect free-surface method of estimating spall strength is still applicable to the GNGs. Finally, the positive gradient structure results in lower temperature and free volume in the spall region, which causes the spall strengths of the S2 sample higher than those of the S1 sample. [ABSTRACT FROM AUTHOR]

The gradient microstructure and deformation mechanisms of an as-cast 6 mm-diameter ZrCuAl metallic alloy are investigated using optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The metallic alloy with gradient microstructure in both phase constituent and grain size from surface to core is prepared based on a fast cooling technique. The quasi-static mechanical property of the alloy is studied and it is found that a good combination of strength-ductility, as well as low Young's modulus and high fracture strength of the alloy are achieved due to the suppression of the strain localization. Combined study of SEM and TEM on deformation mechanisms shows that the gradient microstructure with martensitic transformations, twinnings and dislocations contributes to the enhanced mechanical properties of the large-size metallic alloy. [ABSTRACT FROM AUTHOR]

To optimize the tensile properties of sintered 316L stainless steel fiber felts (SSFFs) which is important for their practical applications, the influence of sintering conditions on the microstructure (fiber ligament, sintering joint) and in turn, the tensile properties was investigated experimentally. It was shown that the tensile strength and tensile elongation of SSFFs were dominated by the tensile properties of the fiber ligaments and the bonding strength of the sintering joints. With the increase of sintering temperature versus holding time, the tensile strength of the fiber ligaments dropped significantly, while the sintering joints grew, producing a higher bonding strength between the fibers, resulting in more fibers being involved in the tensile process. These changes in sintering joints and fiber ligaments finally led to a relatively static ultimate strength of SSFFs with a significantly increased elongation, thus with a large increase in tensile fracture energy. The increase of size of the sintering joints also helped to considerably raise the tensile fatigue limit of 316L SSFFs. This research provides a basis to improve the mechanical properties of sintered 316L SSFFs in industrial production. [ABSTRACT FROM AUTHOR]

• Strength and toughness of fiber reinforced cemented tailings backfill (CTB) were studied. • Polypropylene, polyacrylonitrile and glass fibers were used in CTB as fiber reinforcement agent. • Strength gain of fiber-reinforced CTB showed an increasing trend as the fiber content rises. • Addition of different types of fibers caused a significant change in CTB's toughness. • The crack resistance of fiber-reinforced CTB was remarkably better than that of unreinforced ones. In this paper, an experimental investigation was carried out to study strength, toughness and microstructural properties of early age cemented tailings backfill (CTB) reinforced with three different types of fiber. Polypropylene, polyacrylonitrile and glass fibers were used in CTB to better understand the effect of fiber addition on the backfill's strength and toughness properties. Different fiber contents (0 wt%, 0.3 wt%, 0.6 wt% and 0.9 wt%) and curing times (3 and 7 days) were designed for the preparation of CTB samples with two cement-to-tailings ratios (c / t = 1:4 and 1:6). The results indicated that the addition of different type and content of fibers caused a significant change in CTB's toughness. The fiber content influenced the backfill's strength performance. The strength gain of fiber-reinforced CTB samples showed an increasing trend as the fiber content rises. Linear relationships could be used to express relations between strength gain and fiber content. The peak strain factor K was defined during the toughness tests. K showed a monotonous increasing trend by the increase of fiber content. The polypropylene fiber was larger than polyacrylonitrile, but less than glass fiber when fiber content was 0.3 wt%. The unreinforced CTB samples were mainly parallel to the axial tensile cracks and a small amount of shear cracks, while the deformation of fiber-reinforced CTB was relatively large, it did not break into small pieces. The crack resistance of fiber-reinforced specimens was notably better than that of unreinforced ones. Failure mechanism and modes of fiber addition in CTB samples were also studied. As a result, this study could provide a theoretical/application basis for mines to reduce cement usage within the CTB matrix, achieve safe mine production, increase ore extraction and reduce ore losses and dilution. [ABSTRACT FROM AUTHOR]

Cement-tailings matrix composites (CTMC) have problems such as high brittleness and poor crack resistance when subjected to high stresses corresponding to large depths. To overcome these problems, the feasibility of adding fiber to CTMC were explored by using numerous uniaxial compressive strength, longitudinal wave velocity, splitting tensile, three-point bending resistance tests and scanning electron microscopy analysis. To produce the cemented backfills, three different fibers such as polypropylene fiber, polyacrylonitrile fiber, and glass fiber were used to improve their mechanical strength properties. The quality and performance of fiber-reinforced CTMC structures were compared with non-reinforced ones (without fiber addition). Results show that: (1) the addition of fiber increases the uniaxial compressive and splitting tensile strength, and the load-bearing capacity after the peak of the load-span deflection curve of filling, but the bending strength enhancement effect is not ideal. (2) When the fiber content increases from 0.3% to 0.9%, the uniaxial compressive strength, splitting tensile and flexural strength of fiber-reinforced backfills usually followed a trend of increasing first and then decreasing. Among the fibers, the comprehensive reinforcement effect of polypropylene fiber is the best. (3) Uniaxial compressive strength and longitudinal wave velocity of CTMC followed a function increasing trend y = 0.216 + 0.031 e 1.743 x . (4) The interfacial behavior between the fiber and the matrix is an important factor in suppressing the crack. The addition of fiber causes the failure form of CTMC to transform into the ductile failure. • Cement-tailings matrix composites (CTMC) have problems such as brittleness and crack resistance. • The feasibility of adding fiber to CTMC samples were explored by using several laboratory tests. • To improve CTMC's strength properties, polypropylene, polyacrylonitrile, and glass fibers were used. • Among the fibers, the comprehensive reinforcement effect of polypropylene fiber is the best. • The addition of fiber causes the failure form of CTMC samples to transform into the ductile failure. [ABSTRACT FROM AUTHOR]

Highlights • Dynamic properties of cement-tailings matrix composites (CTMC) was studied. • Increasing the average strain rate led to a remarkable increase in CTMC’s dynamic peak compressive strength (DPCS). • An exponential relation between DPCS value and cement-to-tailings ratio can be defined. • The axial displacement distribution numerical simulation results of the SHPB test was analyzed. • Numerical simulation is very similar to the laboratory result during the SHPB tests. Abstract Investigating the dynamic response of cemented tailings backfill (CTB) is a challenging task since there is a lack of the sophisticated laboratory device and the costs linked with extraction of ore in the stopes using explosives are relatively high. In this study, the variations in the dynamic peak compressive strength (DPCS), cement-to-tailings ratio (c/t), and curing time (CT) of nine types of cement-tailings matrix composites (CTMC) were investigated under impact loading strain rates ranging from 10 s−1 to 100 s−1 using a split Hopkinson pressure bar (SHPB). Physical and chemical characteristics of tailings from a gold mine were tested. A series of dynamical compressive strength test and microstructural analysis were conducted to determine the relationships between DPCS of CTMC and three factors of average strain rate (ASR), cement-to-tailings ratio (c/t) and curing time. A total of 36 CTMC samples with a diameter × height of 50 mm × 25 mm prepared at different c/t (1:4, 1:6 and 1:8) and CT (28, 56, and 90 d) values were subjected to DPCS test. The results shows that: (1) DPCS results increased with an increase in ASR. Different types of curve fitting were conducted to obtain the correlation between DPCS and ASR. An exponential function was used to explain the relationship between DPCS and ASR. (2) As the ASR increases, the dynamic increase factor (DIF) value increases. The exponential function can be used to characterize the quantitative relation between DIF and lgASR. (3) When the results of the experiment and the ANSYS/LS-DYNA numerical simulation were compared, the stress-strain and the failure characteristics of the CTMC and DPCS with impact velocity are consistent. The results of this study can provide significant reference for the backfill design of underground mining. [ABSTRACT FROM AUTHOR]

• The introduction of WGP could improve the pore structure and long-term mechanical properties of CTB. • The pore structure of CTB with WGP is related to the replacement rate of WGP. • The influence mechanism of WGP on the mechanical properties was analyzed. • The optimum replacement rate of WGP for cement on CTB was obtained. In order to reduce the filling cost of the mine and improve the performance of the cemented tailing backfill (CTB), waste glass powder (WGP) is introduced into the CTB as a substitute for cement in this paper. The study examined pore structure, mechanical properties and microstructure changes of CTB samples based on 0, 10, 20, and 30 % WGP replacement rates. The following conclusions are obtained, the pore size of CTB is divided into micropores, secondary pores, and macropores with the boundary of 20 nm and 200 nm, and the pores in CTB are mainly macropores. The incorporation of WGP can improve the pore structure of CTB. The hydration of CTB with WGP can be divided into two parts. Before the curing time is 56d, cement dominated hydration occurs in CTB. WGP mainly plays the role of micro aggregate effect in filling the pores of CTB, and the strength of CTB decreases with the increase of WGP replacement rate. After 56d of curing, cement hydration rate slows down. The pozzolanic activity of WGP is activated under strong alkaline environment, and the secondary hydration reaction enhances the long-term strength of CTB. Especially for CTB with a replacement rate of 20 %, the particle peeling on the surface of the sample is improved after unconfined compression and its microstructure is more compact, the Ca/Si ratio is significantly increased after long-term curing. [ABSTRACT FROM AUTHOR]

• Medium-entropy Ti-Cu-Zr-Pd-Co glass-forming alloys were predicted. • Metallic glasses and their composites were fabricated using rapid solidification. • Transformation-induced-plasticity effect was observed in the annealed states. Since single solid solution tends to form in medium- or high-entropy alloys (MEAs or HEAs), it offers an opportunity to obtain shape-memory type bulk metallic glass (BMG) composites when the selected system belongs to not only BMG but also MEAs or HEAs. Herein, through phase prediction parameters used in MEAs and HEAs, the phase formations for the medium-entropy Ti 40 Cu 36-x Zr 10 Pd 14 Co x (x = 2, 4, and 6 at.%) glass-forming alloys were evaluated before experiments. According to prediction, both fully amorphous samples and BMG composites were fabricated by rapid solidification. To observe the phase formations and the transformation-induced-plasticity (TRIP) effect, fully crystalline MEAs were obtained by annealing. With increasing Co addition, B2 Ti(Pd,Cu) phase can be stabilized to room temperature. All the samples exhibit excellent mechanical properties mainly due to different contributions from the transformation strengthening, second phase strengthening, and dislocations strengthening effects. [ABSTRACT FROM AUTHOR]

The dynamic mechanical properties of the AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) fabricated by drop-casting (DC) and suction-assisted casting (SC) are investigated under different strain rates and temperatures using Split Hopkinson Pressure Bar (SHPB) system. Microstructure analysis is conducted through SEM, EBSD and TEM to reveal the deformation and fracture mechanisms of the present EHEA. The yield strength and flow stresses for both the DC alloy and SC alloy increase with increasing strain rate, but decrease with increasing temperature. A mixture of ductile and brittle fracture morphologies exists in both the DC and SC EHEAs. Moreover, the SC alloy displays more shear dimples on the fracture surface, while brittle fracture features become dominant for the DC alloy. Abundant accumulation of dislocations in the quasi-static test produces slip traces in the FCC lamellar phase which further enhances the plasticity of the SC alloy. Meanwhile, the dislocation cells formed by high-density dislocation tangles at high strain rates, leading to apparent work hardening and strain rate sensitivity of the SC alloy. The adiabatic shear band (ASB) forms in the SC alloy before shear failure and the adjacent twisted and curved lamellar structures play a significant role in preventing shear localization. Overall, the SC alloy exhibits a stronger strain rate effect and better ductility than the DC alloy. [Display omitted] • The AlCoCrFeNi 2.1 with lamellar structures exhibits strong strain rate effect. • The alloy displays high dynamic flow strength and decent ductility. • Dislocations pile-up on FCC/B2 phase boundaries, enhancing strain hardening. • Lamellar structures impede shear localization by twisting and bending. [ABSTRACT FROM AUTHOR]

• Cyclic loading and unloading had obvious influence on the mechanical properties of the CPB, which was closely related to the number of layers and confining pressure. • The change of deformation modulus caused by cyclic loading and unloading is the direct cause of the change UCS. • The different maintenance time of each layer of CPB with multiple layers results in different pore distribution and structure in each layer. At the same time, the confining pressure affects the stress state of the pore. In this paper, an experimental investigation was conducted to study mechanical properties and microstructural characteristic of layered cemented paste backfill (CPB) under triaxial cyclic loading and unloading condition. A number of CPB specimens were prepared with different number of layers (1, 2, 3, and 4). Four confining pressures (0, 0.2, 0.5, and 0.8 MPa) and three cycles were designed. The results indicated that cyclic loading and unloading had obvious influence on the mechanical properties of the CPB, which was closely related to the number of layers and confining pressure. Compared with the conventional triaxial compression test results, when the confining pressure is 0 and 0.2 MPa, the cyclic loading and unloading can increase the uniaxial compressive strength (UCS) of CPB, and when the confining pressure is 0.8 MPa, it decreased the UCS. When the confining pressure is 0.5 MPa, it increased the strength of the CPB 1 and 2 layers, but decreased the strength of CPB with 3 and 4 layers. The change of UCS had a positive linear correlation with the change of secant modulus of unloading curve caused by the cycle loading and unloading. The results of SEM and CT scanning showed that there were more pores in the post filling layers due to the difference of curing time which were compacted easily under small confining pressure. Under the action of cyclic loading and unloading, the CPB was repeatedly compacted, resulting in the increase of UCS. With the increase of confining pressure, the difficulty of pore compaction increases gradually and stress concentration was easy to form around the pores, which resulting in local fatigue damage and reduce the strength under cyclic loading and unloading. [ABSTRACT FROM AUTHOR]

• Strain rate effect on dynamical characteristics of cemented tailings composites (CTC) was investigated. • The dynamic compressive strength of the CTC increased exponentially with average strain rate (ASR) increased. • The fractal dimension of the pore area increased linearly with the ASR increased. The dynamic mechanical properties of the cemented tailings composites (CTC) is one of the major technical challenges in the mining engineering field. In this paper, the Split Hopkinson Pressure Bar (SHPB) impact loading and scanning electron microscopy (SEM) system were conducted to investigate the average strain rate (ASR) rate on the dynamic compressive strength (DCS), microstructure fractal dimension and failure pattern of the CTC specimens. The result shows that the DCS of the CTC increased exponentially with the increase of ASR value when the ASR was in the range of 10–100 s−1. The main hydrate productions of CTC are C-S-H and AFt. The pore size of CTC increased with increased ASR. The fractal dimension of the pore area increased linearly with increased ASR. According to the above results, it provides a reference for engineers of mine sites to reduce the blasting impact load utilizing discontinuous charging and differential detonation, thus achieving the goal of reducing the dilution rate of underground mining. [ABSTRACT FROM AUTHOR]