Mg-6Al-3Ca-1Zn-0.3Mn alloy (mass fraction, %) was prepared by gravity casting, and the alloy was homogenized and differential speed extruded. The effect of differential speed extrusion on the microstructure and properties of different portions of the plates were investigated by using EBSD and TEM, and meanwhile the differential speed extrusion process was analyzed via finite element simulation with Deform-3D. As indicated by the results, that the temperature field and stress field in the extrusion process are the key factors affecting the microstructure of the plate. The temperature at the front end of the plate drops rapidly at the early stage of extrusion, forming a temperature difference with the inside of the die, which results in incomplete recrystallization, and thereby emergence of a large number of un-recrystallized grains. In the late stage of extrusion, the plate temperature is consistent and high, and the billet inside the cavity is subjected to increased stress, which produces partial twinning and promotes dynamic recrystallization. The starting portion of the plate consists of coarse un-recrystallized grains and fine dynamically recrystallized grains, and there is a color gradient within the un-recrystallized grains, and a large number of LAGBs are distributed among the un-recrystallized grains, and the recrystallization mechanism may be continuous dynamic recrystallization. The end portion of the plate consists of equiaxed grains with locally protruding grain boundaries, and the original grain boundaries show jagged shape, and the recrystallization mechanism may be ascribed to discontinuous dynamic recrystallization. Finally, the starting portion of the plate is obtained as the highest tensile strength of 328 MPa, which is due to the combined effect of fine crystal strengthening of the recrystallized grains and dislocation strengthening of the un-recrystallized grains. The end portion of the plate shows the best elongation of about 16.6%, which is mainly due to grain refinement and weakening of the weave structure.

In order to study the deformation behavior of a directionally solidified nickel based high-temperature alloy DZ411 by cyclic loads (20-380 MPa) at temperatures (1173-1223 K) was studied via electronic creep testing machine, optical microscopy and electron field emission scanning electron microscopy etc. Meanwhile a model of the fracture life of the alloy was also established and compared with the test results. The results show that under constant and cyclic loads, the fracture life (t_r) and minimum strain rate ({\dot{\epsilon }}_{\mathrm{m}\mathrm{i}\mathrm{n}}) of the alloy both conform to the Monkman-Grant equation and can be fitted well on the same data set. As the test temperature, stress amplitude, and average stress decrease, the fracture time increases and the internal damage of the alloy intensifies. The minimum strain rate and average stress of the alloy follow a power-law relationship, but considering the comprehensive effect of the average stress (σ_m) and stress amplitude (σ_a) on the fracture life in cyclic testing, the equivalent stress may be corrected according to ({\sigma }_{\mathrm{e}\mathrm{q}}={\sigma }_{\mathrm{m}}^{\gamma }{\sigma }_{\mathrm{m}\mathrm{a}\mathrm{x}}^{\mathrm{1}-\gamma }, γ = 0.1), and the Larson-Miller parameter method (P\left({\sigma }_{\mathrm{e}\mathrm{q}}\right)=T\left[C+\mathrm{l}\mathrm{g}\left(t_{\mathrm{r}}\right)\right]) is used to normalize the fracture life by different loading conditions, thus achieving life prediction by various temperature and loading conditions.

The Q620qENH steel plates were welded via a Gleeble-3800 thermal simulation set, while the welding thermal cycles of varying heat inputs ranging from 10 kJ/cm to 80 kJ/cm were applied. Then the steel and its weld joints were characterized by means of optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), Vickers hardness tester, and low-temperature impact tests, in terms of the effect of heat input on microstructure and mechanical properties of the coarse-grained heat-affected zones (CGHAZ) of weld joints. The results reveal that at lower heat inputs (10 kJ/cm to 40 kJ/cm), the microstructure of the CGHAZs is primarily composed of lath bainite (LB) and a minor fraction of granular bainite (GB), with microhardness values stabilized between 310 and 330HV, and with impact energy at -40 ^oC maintained within the range of 250 J to 300 J. The impact fracture surfaces exhibit a pattern of multi-scale reticular dimples feature. As heat input increases from 50 kJ/cm to 80 kJ/cm, the GB content increases while LB diminishes, a pronounced reduction in the lath bundle structure, significant coarsening of the microstructure, enlargement of the prior austenite grain boundary size, and increased proportion of M/A island constituents, which results in a decrease in microhardness to 253HV. Upon further increasing the heat input from 60 kJ/cm to 80 kJ/cm, there is a significant deterioration in the low-temperature toughness of the steel, with the impact energy at -40 ^oC plummeting from 273 J to 36 J. The impact fracture surfaces display a distinct river-like pattern, indicative of brittle fracture characteristics. This is attributed to the fact that the transition from ductility to brittleness of this grade steel occurs at a heat input of 60 kJ/cm. This is attributed to joints the fact that the transition from ductile-to-brittle of the steel occurs at a heat input of 60 kJ/cm. Consequently, the optimal heat input range for the Q620qENH steel is below 60 kJ/cm to achieve a favorable matching between high hardness and excellent low-temperature toughness.

To enhance the wear resistance of DD5 single crystal superalloy under severe frictional service conditions, CoMoCrSi alloy coating and CoMoCrSi/Y₂O₃ composite coating are fabricated on its surface via laser melting deposition. The microstructure, phase composition, grain size, microhardness, and wear resistance of the coatings are systematically investigated. Results show that by identical processing parameters, the CoMoCrSi/Y₂O₃ composite coating and CoMoCrSi/Y₂O₃ composite coating exhibit a smooth and compact surface without visible cracks or pores, and achieves good metallurgical bonding with the substrate. Compared with the CoMoCrSi alloy coating, the average grain size of Laves phase in the composite coating is reduced by 12.17%. The volume fractions of Co₃Mo₂Si-type Laves phase and Y₅Si₃ secondary phase increase to 50.1% and 0.7%, respectively. The phase formation sequence is as follows: Co-based solid solution precipitates first, followed by the secondary precipitation of Co₃Mo₂Si-type Laves phase, and finally the terminal precipitation of Y₅Si₃ secondary phase. Moreover, the composite coating exhibits an increased average microhardness of 803.4HV_0.5, representing a 10.19% improvement over the CoMoCrSi alloy coating. Correspondingly the average coefficient of friction and the wear mass loss are reduced to 0.308 and 3.2 mg, respectively. It follows that a continuous and compact protective oxide scale forms on the worn surface, which may facilitate effectively the suppressing of plastic deformation and wear damage. These improvements contribute to the significantly enhanced wear resistance of the CoMoCrSi/Y₂O₃ composite coating.

In view of the poor electronic conductivity and low Zn-ion diffusion coefficient of vanadium-based oxides as positive electrode material for aqueous Zn-ion batteries, a novel electrode material Ca²⁺ pre-intercalated V₂O₅ with high specific capacity and good rate performance has been prepared by hydrothermal method with the addition of an appropriate amount of hydrogen peroxide as inductive agent. V₂O₅ with pre-embedding Ca²⁺ has a slightly increased interlayer spacing (about 0.023 nm) on (001) crystal plane, which is beneficial to the embedding/detaching of Zn²⁺ and the improvement of Zn storage performance as the cathode material aqueous Zn-ion battery. The highest specific capacity of Ca²⁺ pre-intercalated V₂O₅ cathode material is up to 242 mAh·g^-1 which is 1.9 times of the product prepared without hydrogen peroxide. After 40 charge-discharge cycles, the specific capacity is 217.26 mAh·g^-1 showing the higher capacity retention rate at low current density. When the current density returns to 0.1 A·g^-1, the capacity retention rate is 95.6%, indicating the enhanced rate performance of Ca²⁺ pre-intercalated V₂O₅ cathode material. The calculation result about the kinematic behavior of Ca²⁺ pre-intercalated V₂O₅ cathode material shows that the high pseudocapacitive control proportion is 52% at the scanning rate of 0.2 mV·s^-1 with the pseudocapacitive proportion increasing as the scan rate increased.

The effect of Mg amount on the performance of Al-Ga-In-Sn alloys as anode for Al-air battery was investigated. The Al-Ga-In-Sn-Mg alloy was prepared by adding trace amount of elements Ga, In, Sn, and Mg to alloy the high-purity Al (4N). The added trace elements mainly contribute to the formation of second phases or precipitates in the Al matrix. As anode material, the electrochemical properties of the Al-Ga-In-Sn-Mg alloy in 4.0 mol/L NaOH solution were assessed by polarization curve measurement, electrochemical impedance spectra, and hydrogen evolution measurement. The results confirm that Mg has the effect of refining the grains and increasing the quantity of the second phase in the Al-alloy. Meanwhile, the corrosion resistance of the Al-Ga-In-Sn-Mg alloy has been improved. The grain refinement enhances the uniformity of the anodic microstructure of the Al-alloy, and the grain boundaries can play a role in hindering corrosion. The Al-Ga-In-Sn-Mg alloy shows an optimal discharge performance when the Mg content is 0.1%. Its discharge voltage is 1.5113 V, its discharge capacity is 2153 mA/cm², and its anode efficiency is 72.26%.

Aiming to practical engineering applications, a quantitative non-destructive testing of stress within the elastic zone of low-carbon steel pipelines was tentatively studied via ultrasonic. Herewith, a two-wave method for measuring the the axial stress of pipes was proposed by taking the transverse isotropic characteristics and acoustic elasticity of low-carbon steel pipe materials into consideration,while the stress-acoustic time equation of the two-wave method was also established. Further, a method combining S-transform and cross-correlation is proposed to overcome the problem related with the low sensitivity of sound waves to low-stress regions so that to improve the accuracy of time measurement. Next, the axial compressive stress of a low-carbon steel pipes of 13 mm in thickness and 168 mm in outer diameter was measured by single-wave method and the double-wave method comparatively. The results proved that the double-wave method could achieve better linearity than the single-wave method, and the accuracy of stress measurement was improved by approximately 3%.

The influence of prolonged high-temperature aging on the microstructural evolution and mechanical properties of GH4169 nickel-based superalloy was investigated. The results demonstrate that the standard heat-treated alloy primarily consists of a γ-phase matrix with trace amounts of short rod-shaped δ-phase (0.139% volume fraction, 0.32 μm in size) distributed along grain boundaries, achieving optimal mechanical properties: yield strength 1330 MPa, ultimate tensile strength 1385 MPa, and hardness 497HV, albeit with limited ductility 19.75% reduction of area. During aging at 900 °C for 500-1134 h, the metastable γ'' phase progressively transforms into δ-phase (Ni₃Nb), accompanied by a substantial increase in δ-phase content (14.2% at 500 h and 15.1% at 1134 h) and coarsening from 2.65 μm to 2.86 μm. The δ-phase evolves distinct microstructural characteristics: intergranular short-rod fragmentation and intragranular oriented needle-like precipitation. Significant aging effects are observed, manifesting as a 57% hardness reduction, 34% yield strength decline, 19% decrease in impact toughness, and an 80% ductility improvement. Mechanistic analysis reveals that initial grain-boundary δ-phase enhances the strength via grain refinement through Zener pinning. However, prolonged aging induces δ-phase coarsening at grain boundaries, which consumes γ'' strengthening precipitates and weakens the matrix. Concurrently, high-temperature aging promotes direct intragranular δ-phase precipitation, deteriorating the precipitation strengthening efficacy. Fractography transitions from equiaxed dimples (ductile fracture) in the standard condition to a ductile-brittle mixed mode featuring willow-leaf-shaped dimples and cleavage planes in the aged alloys, with δ-phase interfaces acting as preferential pathways for crack propagation. These findings elucidate the critical role of δ-phase evolution in governing the strength-ductility trade-off during high-temperature aging.

Composite of diamond particulates/copper was fabricated through diffusion bonding with a thin Ni-foil as interlayer via a spark plasma sintering technique. Then the formed bonding interface was characterized by means of SEM+EDS, XRD, universal testing machine and thermal conductivity meter, in terms of its microstructure, fracture morphology, shear strength, and thermal conductivity. Meanwhile the effect of process parameters on the microstructure and thermal conductivity of the bonding interface was investigated, and the variation of the interface behavior during diffusion bonding process was also studied by the first principle calculation. The results showed that the formed interface presents excellent metallurgical bonding between the diamond particulates and the Cu. The presence of the thin Ni foil interlayer significantly reduced the formation of voids and holes at the diffusion-bonded interface. The diffusion of Ni led to the formation of an α single-phase Cu-Ni solid solution and the production of the Ni₃C phase. The phonon and electron density of states maps of the Cu/Ni-interface showed that the thermal conductivity of the binary interface was better than that of the diamond/nickel interface, and the high proportion of Cu/Ni-interface connection at the interface was an important factor in achieving high thermal conductivity. The spark plasma sintering induced diffusion joint interface presents thermal conductivity up to 703.83 W/(m·K), while the infinite solid solution of Ni-Cu, as well as the generation of carbide is conducive to the thermal conductivity of the joint.