The effect of rolling temperature on microstructure evolution and mechanical/thermal properties of Mg-4Zn-1Mn-1.2Ce alloy was investigated. Results indicate that Mg-Zn-Ce (τ phase) second phase and α-Mn were crushed and distributed along the rolling direction in the as hot-rolled Mg-4Zn-1Mn-1.2Ce alloy. When the rolling temperature was lower than 400^oC, most grains became deformed grains, but the proportion of recrystallized grains increased due to the occurred static recrystallization during heat preservation in the intervals between rolling-passes when the plate was rolled at 425^oC. The tensile strength, yield strength and elongation of the rolled Mg-4Zn-1Mn-1.2Ce alloy sheet were 386 MPa, 356 MPa and 4.8%, respectively, as well as the thermal conductivity of 127.3 W·(m·K)^-1 when it was hot-rolled at 375^oC. Annealing has resulted in a slight decrease in strength, but a great improvement in toughness. In the case of the alloy rolled at 375^oC, its elongation increased from 4.8% to 23.5% after annealed at 400^oC/60 min. Also, the thermal conductivity of the annealed alloy decreased about 4~9 W·(m·K)^-1 in comparison with that of the as-rolled one.

The effect of mixed rare earth elements Ce and La on the microstructure and mechanical properties of Al-Zn alloy was studied by means of metallographic (OM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), hardness tester and wear resistance test. The results show that after the addition of Ce and La, the Al-Zn alloy presents microstructure composed of three phases: eutectic Al₁₁Ce₃ and Al₁₁La₃ phases distributed along the grain boundaries and punctate iron-rich phases distributed in the matrix, furthermore, a rod-shaped primary Al₁₁Ce₃ phase may emerge when 0.75%RE is added. With the increase of mixed rare earth content, the grain of Al-Zn alloy is gradually refined, while the grain size is the smallest when the rare earth content is 0.75%, which is about 151 μm. The smaller the grain size, the higher the hardness and wear resistance of the alloy. Among others, the hardness is the highest, about 27.5HV, and the wear resistance is also the highest, the average friction factor is 1.076, and the average wear rate is 36.5 mg·N^-1·m^-1 for the alloy with addition of 0.75% mixed RE. In the process of friction wear, abrasive wear, peeling wear and plastic deformation mainly occur for the Al-Zn alloys.

Silicon carbide (SiC) as a kind of high temperature absorbing materials has great application potential, but its application range is limited due to high preparation cost. Herein, the SiC absorbing materials by in-situ reaction of pyrolytic carbon and silicon powder were prepared in vacuum at 1800^oC, 2000^oC and 2200^oC respectively, aiming to clarifying the relevant reaction mechanism so that to search the way for saving preparation cost. The microstructure, phase composition and electromagnetic properties of the three kinds of SiC materials were assessed. The results show that during the in-situ reaction of SiC preparation, the β-phase SiC with 3C crystallographic structure is formed at 1800^oC, while at 2000^oC the β-phase SiC begins to transform into α-phase SiC with 6H crystallographic structure via evaporation and condensation processes. With the increase of the reaction temperature, the degree of phase trasformation reaction was gradually intensified. Spontaneously, the proportion of α phase SiC also increases gradually, and the dielectric loss ability of the corresponding SiC materials to electromagnetic waves is gradually weakened, the impedance matching performance is gradually improved. In brief, the prepared SiC material presents appropriate comprehensive performance of dielectric loss and impedance matching when the preparation temperature is set above ≥ 2000^oC, suitable for use as a wave absorbing material. The results show that it is feasible to prepare SiC absorbing materials with low preparation cost by in-situ reaction method.

Two pre-powders of GH4099 alloy were prepared via techniques of plasma rotating electrode process (PREP) and electrode induction melting gas atomization (EIGA) respectively. Then, the powders were subjected to hot isostatic pressing (HIP) to prepare bulk GH4099 alloy (PM GH4099 alloy), and the effect of HIP temperature on the microstructure and tensile properties of PM GH4099 alloy was investigated. The results show that in comparison with EIGA process, the GH4099 powder prepared by PREP process has better powder sphericity with thinner surface oxide scale, which is more suitable for hot isostatic pressing preparation of workpiece of PM GH4099 alloys. With the increasing HIP temperature within the range of 1165^oC~1230^oC, the porosity and prior particle boundaries (PPBs) of the acquired PM GH4099 alloy decreases significantly, therewith, the corresponding tensile properties at 900^oC were improved. Finally, with the help of finite element modeling (FEM) to assist the envelope design and make, and finally thin-walled cylinders of PM GH4099 were successfully fabricated with the PREP powder via HIP at 1230^oC/150 MPa/4 h. The FEM predicted dimensional shrinkages are consistent with that of the actual made thin-walled cylinders of PM GH4099, and the deviation between the corresponding key dimensions is less than 5%.

High-entropy oxides (HEOs) have attracted widespread attention as the next-generation anode materials for lithium-ion batteries (LIBs) due to their low cost and high theoretical capacity. In this work, for the first time, a series of spinel-type cobalt-free (Cr_0.2Fe_0.2Mn_0.2Ni_0.2X_0.2)₃O₄ (X = K, Mg, Zn) high-entropy oxide powders as anode materials for LIBs were synthesized via a solution combustion method. The microstructural features and electrochemical performance of the powders were systematically investigated in comparison with cobalt containing powders of (Cr_0.2Fe_0.2Mn_0.2Ni_0.2Co_0.2)₃O₄. The results indicate that the prepared high-entropy oxide powders are all single-phase of spinel structures, with a porous reticular morphology and uniform distribution of constituent elements. When used as anode materials for LIBs, cobalt-free (Cr_0.2Fe_0.2Mn_0.2Ni_0.2Zn_0.2)₃O₄ exhibits excellent lithium storage performance. After 150 cycles at a current density of 200 mA·g^-1, its reversible specific capacity is up to 1303 mAh·g^-1. Furthermore, after 380 cycles at a high current density of 1000 mA·g^-1, the reversible capacity can still reach 1190 mAh·g^-1 (both are higher than its theoretical capacity of 908 mAh·g^-1). The reasons for the excellent lithium storage performance of 4MZn electrode are: high specific surface area, mesoporous structure, and abundant oxygen vacancies on the surface make it a high conductivity (12.2 S·m^-1) and a large pseudo-capacitance contribution rate; At the same time, the addition of active element Zn causes the formation of Li-Zn alloy in the reduction process of 4MZn electrode, thereby increasing its specific capacity. This work provides a new design approach for exploring cobalt free high entropy energy storage materials with low cost and excellent electrochemical performance.

In this paper, thermal barrier ceramic coatings (TBCs) with columnar-like structure were prepared on high temperature alloys N5 and DZ411 by suspension plasma spraying, using tetragonal yttria stabilization zirconia (YSZ) powder as raw material. The failure behavior of TBCs was assessed by thermal cycling test (i.e. furnace heating to 1100^oC for 60 min. and then air cooling for 10 min. as one cycle), and flame thermal shocking test (i.e. quick flame heating to 1300^oC and then compressed air cooling to below 300^oC as one cycle) respectively. The results show that the coatings have excellent resistance to thermal cycling and flame thermal shocking, and the phase composition of ceramic coatings maintains tetragonal crystallographic structure after all the tests. The failure mechanism of TBCs in thermal cycling and flame thermal shocking is different. Delamination failure occurs at the interface between the ceramic layer and thermal grown oxides (TGO) during thermal cycling, caused by the mismatch of different thermal expansion coefficient. Besides, the main failure source of TBCs during flame thermal shocking is severe internal oxidation of bond coat due to the formation of hot channel, which is converted from gaps between columnar.

Two Al-Mg-Si alloys with different Fe-rich phase contents within a range of low Fe-rich phase content were designed, and the effect of Fe-rich phase on microstructure, texture and mechanical properties of the alloys were studied through microstructure characterization, texture measurement and tensile test. The results show that the shape and size of the Fe-rich phase may undergo continuous changes during thermomechanical processing, especially for the intermediate annealing state, and some coarse particles of Fe-rich phase could become nano-sized; although the introduction of the Fe-rich phase affects the microstructure of the intermediate states slightly during thermomechanical processing, it may be beneficial to efficiently refine the final recrystallization grain structure; Fe-rich phase can affect recrystallization texture and volume fractions, and thus the final weak recrystallization texture may be developed; Fe-rich phase is beneficial to improve yield strength, ultimate tensile strength and plastic strain ratio r, reduce strain hardening exponent n and planar anisotropy coefficient, and keep elongation unchanged. The improvement of properties can be attributed to the fine microstructure and weak texture.

The fatigue crack propagation of heavy rail steel has a very complex relationship with the stress and strain at the crack tip, but there is currently little research on this mechanism. This article takes pearlite heavy rail steel as the research object under three conditions (increasing cooling rate): online rolling state, online heat treatment state, and laboratory heat treatment state. The pearlite layers at different cooling rates were observed using scanning electron microscopy, and the tensile fatigue crack and stress field cloud map at the crack tip of the heavy rail steel were measured using fatigue testing machines and strain gauges. Then, a stress and strain model was established based on Abaqus, the results indicate that as the cooling rate increases, the interlayer spacing of pearlite decreases; With the fatigue crack propagation, the stress field strength around the crack and the Stress intensity factor k at the crack tip increase, and the stress field is more significant in the "butterfly" shape. The Stress intensity factor of the laboratory heat treated heavy rail steel at the crack length of 1, 2, 3 mm is 13.53, 14.58, and 15.54 MPa·m^1/2, respectively, which is far greater than that of the rolled and heat treated heavy rail steel at the same crack length; As the fatigue crack length increases, the equivalent strain area near the crack tip increases. At the same crack length, the equivalent strain at the crack tip of three kinds of heavy rail steels with cooling rate decreases with the decrease of pearlite lamellae. The simulation results of equivalent strain at a longer crack length of 3 mm are 0.074, 0.067 and 0.055 respectively, while the strain experimental results are 0.082, 0.064 and 0.058 respectively. The maximum error between the simulation results and the strain field experimental results is 5.1%, which verifies the model. Both simulation and experimental results show that the smaller the pearlite lamella is, the larger the Stress intensity factor at the crack tip is during the fatigue crack growth process of heavy rail steel, the smaller the equivalent strain area is, the stronger the fracture resistance is, and the better the fatigue performance is.