Metals and Materials International最新文献

 Sb is one of the tramp elements that remain in molten steel during the steelmaking process. It is generally known to be difficult to remove it from the molten steel. In order to develop a feasible process to remove Sb from molten steel, the evaporation reaction of Sb from molten steel was investigated by high-temperature liquid–gas experiments using an electromagnetic levitation melting technique and kinetic analysis. The evaporation rate of Sb was measured by varying the flow rate of incoming gas (Q), temperature (T), initial C content ([pct C](_0)), and initial S content ([pct S](_0)) in molten Fe–C–S–Sb alloys. It was found that the evaporation rate of Sb accelerated by S due to the formation of the sulfide gas species (SbS(g)) and by C due to increasing the activity coefficient of Sb ((f_{textrm{Sb}})) and S ((f_{text {S}})). On the other hand, the evaporation rate of Sb decelerated by S due to the blocking of the molten steel surface. Based on the established mechanism, a model of Sb evaporation from molten Fe–C–S–Sb alloy was developed in the present study, which considers (1) actual evaporating species, (2) surface blocking by S using ideal Langmuir adsorption, and (3) effect of C and temperature on (f_{text {Sb}}) and (f_{text {S}}). With the established model, the extent of Cu, Sn, and Sb removal in the molten steel was assessed. It turned out that Cu has the fastest removal rate, followed by Sb, with Sn being the slowest for molten steel containing 0.1 pct C and 0.01 pct S at 1650 (^circ )C.

In this study, a cold-pilgered Zr alloy tube with the composition of Zr-1.0 wt%Sn-1.0 wt%Nb-0.3 wt%Fe was investigated. During the cold pilgering, the tube developed distinct microstructural and textural features at different positions (with varying internal/external diameters and wall thicknesses) due to their specific stress states and deformation amount. Microstructural and textural evolution during cold pilgering were analyzed by characterizing specimens (S0-S4) cut from typical tube positions mainly using electron channeling contrast imaging and electron backscatter diffraction techniques. Transmission electron microscopy was also utilized to reveal typical precipitates in the un-pilgered specimen (S0). Results indicate that at low/medium strains, there exist non-deformation grains with hard orientations in the pilgered tube specimens, leading to heterogeneous microstructures. With increasing strains, the tube specimens show continuously reduced grain sizes and increased kernel average misorientations along with higher fractions of low angle boundaries, resulting in enhanced microstructural homogeneity. During the pilgering, the texture of Zr-1.0Sn-1.0Nb-0.3Fe alloy tube gradually transforms from initial c//TD to c//RD, which changes back to the c//TD at high strains (>∼ 60%). In the meantime, the < 10–10>//AD component is initially weakened slightly but then significantly enhanced, while there is an opposite trend for that of the < 11–20>//AD component. According to the analysis of in-grain misorientation axes, the textural evolution during the pilgering results from the coordination of multiple slip systems and the pyramidal slip can be substantially activated at a high strain.

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The cold rolling and annealing treatment were applied to the face-centered cubic FeCoCrNiMn high-entropy alloy (HEA). The study investigated the heterogeneous microstructure and mechanical properties of FeCoCrNiMn HEA under different annealing temperatures and rolling reduction amounts. The results show that, when annealed at 600 ℃ − 700 ℃, it is beneficial for obtaining a heterogeneous microstructure composed of fine grains, deformed grains and precipitated phases. Due to the multiple strengthening mechanisms caused by the heterogeneous microstructure, the FeCoCrNiMn HEA exhibits excellent tensile properties, achieving a better balance of strength and plasticity. With a primary rolling and annealing treatment at 650 ℃ for 1 h, the recrystallization volume fraction is 50%, and the yield strength, ultimate tensile strength and elongation are 730.66 MPa, 909.67 MPa and 23.60% respectively, indicating high strength and ductility. With the increase of the annealing temperature, the precipitation of Cr-rich σ phase becomes more evident, the maximum volume fraction of σ phase is 1.96%, and the yield strength is increase by 41.65 MPa due to precipitation strengthening. With the increase of the degree of recrystallization, a phenomenon of texture component weakening and texture randomization occurs, but the main rolling textures, such as P-type and B-type textures, are still retained.

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Cu particles with porous surface are fabricated and used as the paste fillers for rapid sintering. The particles are manufactured by the formation of Cu₅Zn₈ on the surface of the Cu particles, followed by dezincification. The porous structure formed on the surface of the Cu particles collapses owing to external compression during sinter bonding and the in situ formation of Cu nanodebris, thereby enhancing the sinter-bondability. The sinter bonding was performed under 10 MPa at 300 °C in air. Higher shear strength was measured for the paste containing Cu particles with a porous surface compared to the identical sized spherical Cu particles at all bonding times. In particular, a near-full-density bondline was formed after bonding for 3 min and the shear strength increased to 15.85 MPa. When bonding was maintained for 10 min, an excellent shear strength of 20.17 MPa was obtained.

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Zr-containing aluminum-based alloys and especially Al-Zr composites have high thermal resistance due to the formation of Al₃Zr dispersoids from supersaturated aluminum solid solution. The use of mechanical alloying can significantly increase the solubility of zirconium and improve the strength properties at elevated temperatures. The aim of the present work is to investigate the effect of multi-directional forging (MDF) on the microstructure and properties of Al-Cu-Mn alloy mechanically alloyed with 5 wt%Zr. Mechanical alloying was carried out by ball milling for 20 h at 300 rpm. The temperature of hot pressing and subsequent MDF operation was 400 °C. SEM, XRD and TEM were used to study the microstructure. In this work, it was shown that MDF leads to the formation of a poreless structure compared to hot pressing due to strain accumulation during hot deformation, as well as grain growth and microhardness reduction. At the same time, the highest compressive yield strength at 350 °C of 132 MPa was achieved after forging. The obtained material consisted of nanocrystalline aluminum matrix and secondary precipitates of Al₃Zr with cubic (L1₂) and tetragonal (D0₂₃) lattices as well as Al₂₀Cu₂Mn₃ phase.

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This study investigated a strategy for simultaneous improving in the strength and ductility of the directly quenched ultra-high strength low alloy steel via low-temperature tempering. To stabilize the microstructure, sub-zero treatment was also employed at -73 °C for 30 min, and then tempering was performed for two types of temperature at 200 °C and 630 °C for 30 min. The microstructure of as-quenched steel consists of lath martensite and meta-stable retained austenite. After low temperature tempering (200 °C), some stable reverted austenite was formed at the austenite/martensite interface. When tempering was performed at high temperature (630 °C), the entire austenite remained as reverted austenite. In addition, Ti-rich carbides were observed at the martensite lath boundaries during tempering treatment. Tensile strength increased up to ∼ 1.8 GPa after low-temperature tempering, and ductility was also higher than that of as-quenched steel. In contrast, the steel which was tempered at 630 °C shows low mechanical properties compared to the as-quenched steel. Correlations between microstructure evolution (meta-stable to stable austenite transformation), mechanical properties and deformation behavior were also discussed and identified.

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