Search

The NiCoCrFeAlW eutectic high-entropy alloy exhibits a balanced combination of ductility and strength. This study examines the microstructure evolution and mechanical properties of the Ni30Co30Cr10Fe10Al18W2alloy at varying growth velocities (10, 20, 50, 100, and 200 μm/s), which in its as-cast state, features a microstructure that includes both coarse dendrites and lamellar eutectic. The structure of the coarse dendrites is characterized by an ordered body-centered cubic (B2) phase, while the lamellar eutectic, features a combination of face-centered cubic (FCC) and ordered B2 phases. The microstructure, characterized by lamellar and dendritic structures that are parallel to the growth direction after directional solidification, undergoes a morphological transition at the solid-liquid interface from a planar to a dendritic form as growth velocity increases. The tensile fracture strength initially increases with the growth velocity, reaching a peak of 1286 MPa at a velocity of 50 μm/s, and then subsequently decreases as the growth velocity continues to increase. Directional solidification results in an increase in sample elongation with increasing growth velocity, achieving an elongation of 22.5% at 200 μm/s. An examination of the deformation mechanism reveals that the lamellar structure, composed of the more ductile FCC phase and the harder B2 phase, effectively harmonizes the plasticity and strength of the alloy. Therefore, directional solidification significantly adjusts the eutectic microstructure's orientation, thereby enhancing the mechanical properties along the direction of solidification.

With the rapid development of the automobile industry, automobile manufacturers begin to pay more attention to NVH (Noise, Vibration, Harshness). The sound of car closing the door is one of the characteristics of NVH. Therefore, it is of great significance to analyze and improve the door closing sound quality of cars to improve the comprehensive performance of automobile. The dynamic characteristics of car door closing can indirectly reflect the sound quality of car door closing. In this paper, firstly, a finite element model of a quarter of car body with the complete structure of door, window and sealing system was established by HyperMesh software. Secondly, stress-strain tests of sealing strip were performed, and their data were input into the hyperelastic material setting in ABAQUS for selecting the most suitable strain energy function. Thirdly, the sealing strip model was introduced into ABAQUS, a simulation of reaction force and compression displacement on the sealing strip was performed by ABAQUS to generate the sealing strip CLD curve, and be verified by test. Fourthly, the finite element model was introduced into ABAQUS, the Y-direction (rightward direction from driver) acceleration of the three specified points at door closing, such as the upper corner of the door, the midpoint of the window and the body points on the B-pillar, were studied numerically. Finally, their Y-direction jitter acceleration were studied numerically and experimentally. The results showed that the relative error between calculated and experimental maximum values of Y-direction jitter acceleration at three specified points at door closing is less than 5.5%, and the acceleration attenuation trend is consistent with the test.

In the present work, the solidification behaviors and microhardness of directionally solidified AlCoCrFeNi2.1eutectic high-entropy alloy (EHEA) obtained at different growth velocities are investigated. The microstructure of the as-cast AlCoCrFeNi2.1EHEA is composed of bulky dendrites (NiAl phase) and lamellar eutectic structures, indicating that the actual composition of the alloy slightly deviates from the eutectic point. However, it is interesting to observe that the full lamellar structure of this alloy is obtained through directional solidification. In order to explain this phenomenon, the maximum interface temperature criterion and the interface response function (IRF) theory are applied to calculate the velocity range of the transition from the primary phase to the eutectic, which is 1.2–2 × 104μm/s. Furthermore, microhardness is one of the important parameters to measure the mechanical properties of materials. Therefore, the microhardness test is performed, and the test result indicates that the microhardness (HV) increased with increasing growth velocity (V) or decreased with increasing lamellar spacing (λ). The dependences of λand HV on Vare determined by using a linear regression analysis. The relationships between the λ, Vand HV are given as: λ=11.62V-0.48, HV = 305.5V 0.02and HV = 328.1λ−0.04, respectively. The microhardness of the AlCoCrFeNi2.1EHEA increases from 312.38 HV to 329.54 HV with the increase in growth velocity (5–200 μm/s). Thus, directional solidification is an effective method to improve the mechanical properties of alloys.

Compared with the growing applications of peritectic alloy, none research on the freckle formation during peritectic solidification has been reported before. Observation on the dendritic mushy zone of Sn-36 at.%Ni peritectic alloy during directional solidification at different growth velocities shows that the freckles are formed in two different regions: region I before peritectic reaction and region II after peritectic reaction. In addition, more freckles can be observed at lower growth velocities. Examination on the experimental results demonstrates that both the temperature gradient zone melting (TGZM) and Gibbs-Thomson (G–T) effects have obvious influences on the morphology of dendritic network during directional solidification. The current theories onKI Rayleigh number R a characterizing the thermosolutal convection of dendritic mushy zone to predict freckle formation through the maximum of R a can only explain the existence of region I while the appearance of region II after peritectic reaction cannot be predicted. Thus, a new Rayleigh number R aP is proposed in consideration of evolution of dendritic mushy zone by both effects and peritectic reaction. Theoretical prediction of R aP also shows a maximum after peritectic reaction in addition to that before peritectic reaction, thus, agreeing well with the freckle formation in region II. In addition, more severe thermosolutal convection can be predicted by the new Rayleigh number R aP at lower growth velocities, which further demonstrates the reliability of R aP in describing the dependence of freckle formation on growth velocity. [ABSTRACT FROM AUTHOR]

Compared with the growing applications of peritectic alloys, none research on the fluid permeability K of dendritic network during peritectic solidification has been reported before. The fluid permeability K of dendritic network in the mushy zone during directional solidification of Sn-Ni peritectic alloy was investigated in this study. Examination on the experimental results demonstrates that both the temperature gradient zone melting (TGZM) and Gibbs-Thomson (G–T) effects have obvious influences on the morphology of dendritic network during directional solidification. This is realized through different stages of liquid diffusion within dendritic mushy zone by these effects during directional solidification. The TGZM effect is demonstrated to play a more important role as compared with the G–T effect during directional solidification. Besides, it is shown that the evolution of dendrite network is more complex during peritectic solidification due to the involvement of the peritectic phase. Through the specific surface S V , analytical expression based on the Carman–Kozeny model was proposed to analyze the fluid permeability of dendritic mushy zone in directionally solidified peritectic alloys. In addition, it is interesting to find a rise in permeability K after peritectic reaction in both theoretical predication and experimental results, which is different from that in other alloys. The theoretical predictions show that this rise in fluid permeability K after peritectic reaction is caused by the remelting/resolidification process on dendritic structure by the TGZM and G–T effects during peritectic solidification. [ABSTRACT FROM AUTHOR]

In this work, CoCrFeNiMo0.35high entropy alloy was hot-rolled at 900°C by varying different reductions (10%, 20%, 30%, 40%, 50%) and the impact of hot rolling on the structure and mechanical properties of this alloy has been investigated. It is found that the phase composition of CoCrFeNiMo0.35high entropy alloy after hot rolling has not been changed, and it still consists of FCC phase and σ phase (Cr and Mo-rich phase), which is the same as the as-cast state alloy. Besides, the grain size becomes finer after hot rolling and is stretched to a flat shape in the rolling direction, and the grain orientation gradually changes from <001> and <101> direction to <101> direction with the increase of reduction. At the same time, as the increase of rolling reduction, the volume fraction of σ phase increases, and the yield strength (∼817.8 MPa), tensile strength (∼891.7 MPa) and hardness of the alloy are improved. The comprehensive influence of fine grain strengthening, second phase strengthening and dislocation strengthening is the main reason for this result. Besides, the fracture mode of the tensile sample changes from mixed tough-brittle fracture to brittle fracture. The research results can be used as a reference for hot rolling strengthening of CoCrFeNiMo0.35high entropy alloy.

Zr 61.7 Al 8 Ni 13 Cu 17 Sn 0.3 bulk metallic glass samples with different aspect ratios in the range of 0.25–2.25 were deformed by compression, and the effect of aspect ratio on the evolution of shear bands was investigated. It is found that for the deformed Zr 61.7 Al 8 Ni 13 Cu 17 Sn 0.3 bulk metallic glass, the average shear band spacing decreases and the shear band density increases monotonically as the aspect ratio increases from 0.25 to 2.25. A minimal average shear band spacing of 0.478 µm is achieved for the sample with an aspect ratio of 2.25. In addition, the fractions of shear bands with spacings below 100 and 50 nm are about 12.84% and 6.76%, respectively, for the sample with an aspect ratio of 2.25. The reason for the formation of a higher density of shear bands can probably be attributed to the increase of the driving force for the sample with a larger aspect ratio. [ABSTRACT FROM AUTHOR]

Because of the storage and safety of hydrogen on board vehicles, there still exist many problems; this paper introduces a system of hydrogen-rich gases and its application to an electronically controlled spark ignition engine. The hydrogen-rich gases from the designed reformer are produced by methanol dissociated by the heat recycled from the exhaust emissions of an engine. The effects of the hydrogen-rich gases on the performances of the engine were investigated for lean-burning operations. The test results indicate that the engine can operate using a very lean fuel mixture owing to the wide ignition limits of the hydrogen-rich gases. When the excessive air-to-fuel ratio is higher than 1.4, the nitrogen oxide emissions are reduced by 90%, the carbon monoxide emissions are ultra-low, and the hydrocarbon emissions are at nearly the same level as those produced from a gasoline engine. In addition, while maintaining the power output of the engine, lean burning of the hydrogen-rich gases and partial recycling of the exhaust heat significantly improve the brake thermal efficiency of methanol.

No relevant conflicts of interest to declare.

The third-generation tyrosine kinase inhibitor (TKI) ponatinib exhibits activity against all common BCR-ABL1 kinase domain (KD) single mutations, including the highly resistant gatekeeper T315I. However, the drug response is variable and the clinical resistance mutations may still befall with few reports to date. We performed next-generation sequencing (NGS) detection of BCR-ABL1 KD mutations in sequential samples of three BCR-ABL1-positive leukemia patients who developed clinical resistance to ponatinib, to explore the dynamic evolution of ponatinib mutations.