Acta Metallurgica Sinica-English Letters最新文献

The oxidation behavior and kinetics of Ti₂AlC–20vol.%TiB₂ composite at 600–900 °C in air were investigated. The results showed that the oxidation kinetics of the composite followed a logarithmic law within the given temperature range, which indicated that the composites had excellent oxidation resistance. The selective oxidation of Al in Ti₂AlC was greatly enhanced, which facilitated the formation of a continuous and dense protective layer of Al₂O₃. Meanwhile, the existence of molten B₂O₃ inhibited the outward diffusion of Ti and inward diffusion of oxygen, which prevented the growth of anatase TiO₂ at 600 °C and rutile TiO₂ at 700–900 °C. Therefore, the incorporation of TiB₂ completely inhibited the abnormally rapid oxidation of bulk Ti₂AlC at 600 °C and improved its oxidation resistance at 700–900 °C.

The equiatomic TiNbZrTaHf alloy was successfully rolled at room temperature with the reduction of ~ 85%. The microstructure and tensile properties were investigated after cold working and annealing. It was determined that the recrystallization temperature of the TiNbZrTaHf alloy between 850 and 900 °C. Complete recrystallization and normal grain growth occurred, the high stability of single phase was maintained after annealing at 1000, 1200, and 1400 °C. But the precipitated phase appeared after long term annealing, as seen after 500 h at 1000 °C. After cold working, the tensile strength and the elongation of TiNbZrTaHf were 1137 MPa and 25.1%, respectively. The annealed alloy has a high tensile strength (σ_b = 863 MPa) and ductility (ε_e = 28.5%). Moreover, the oxidation of TiNbZrTaHf alloy at elevated temperatures has a significant impact on its mechanical properties. The poor oxidation resistance of TiNbZrTaHf can accelerate tensile failure by inducing fractures at grain boundaries.

In aero-engines, abrasive coatings are typically utilized to protect the blade tip from excessive wear caused by the harder abradable sealing coating and thereby improve the sealing performance of engines. Therefore, a Ni/cBN abrasive coating was prepared on titanium alloy using electrodeposition. The high-speed rubbing tests with a linear velocity of 350 m/s and different incursion rates were performed to investigate the effect of the Ni/cBN abrasive coating on the wear behavior against NiCrAl/diatomite seal coating. Results showed that melting wear and adhesive transfer occurred on the bare blades, causing the bare blade to suffer excessive wear. While the Ni/cBN abrasive coating exhibited superior wear resistance and cutting performance. The cBN grits pullout, the abrasion of Ni matrix and transfer of seal coating to the cBN grits were the main wear mechanism of the Ni/cBN abrasive coating. Additionally, it was found that the relationship between the incursion rate and high-speed rubbing behavior is quite different for the bare blade and Ni/cBN coating. The reason for the difference in wear behavior of bare blade and Ni/cBN coating at different incursion rates was discussed in detail.

The primary focus during surgery is to ensure successful implantation by achieving long-term and stable fixation of implants. Orthopaedic surgery is now more focused on the development of novel biomaterials intended to improve implant performance. To obtain a better understanding of metal implants, this article investigated the causes of material failures in certain cases and analysed a few case studies. The interaction between the implant and bone tissue was a crucial aspect of successful implantation, and this study explored the factors influencing this interaction as well as ways to improve it. Several modern approaches used for modifying implant surfaces were systematically illustrated and briefly analysed. Thermal spray coatings were often favoured because of their wide range of coating materials, but other substantial surface modifications (such as friction stir processing and laser surface texturing) were also used for a selection of applications. Notably, implant surfaces with desirable features, such as biocompatibility, antibacterial properties, corrosion resistance, and wear resistance, were essential for optimising implant functionality. This systematic review's main aim is to provide exhaustive reference information and a broad overview to advance the production and design of orthopaedic implants.

This research systematically examined the degradation, antibacterial effects, and biocompatibility of micro-arc oxidation (MAO) coatings with nano CuO and ZnO on extruded Mg alloys. Both copper (Cu) and Zinc (Zn) possess antibacterial properties. The findings demonstrated that adding ZnO will appreciably reduce the degradation rate of MAO-coating alloy due to the self-sealing micro holes. CuO + MAO coating exhibited excellent antibacterial performance, with an antibacterial rate of over 90% within 6 h co-cultured with Staphylococcus aureus. Similarly, the antibacterial rate of ZnO + MAO coating reached 90% after 12 h co-culture. Cytotoxicity test using MG63 cell indicated that the incorporation of CuO and ZnO did not notably affect the cell viability rate of the coating. Moreover, after 14 days of culture, the CuO + MAO and ZnO + MAO coated samples exhibited higher alkaline phosphatase (ALP) activity than the MAO-coated and uncoated samples, suggesting favorable osteogenic properties.

This work investigated the gradient microstructure evolution and tensile property of LPBF fabricated 15-5 precipitation hardening stainless steel in post-process direct ageing (DA) and solution treating & ageing (STA). The varied microstructures for austenite and small-sized oxide inclusions at different sample heights in the as-built (AB) condition was generally preserved after DA treatment. However, austenite was almost disappeared, and oxide particle grew significantly after the STA treatment. As a result, the tensile property differences in sample top and bottom for AB and DA conditions did not occur in the STA samples. For the influence of post-process heat treatment, the STA condition had the highest yield strength due to the highest volume fraction of nano-sized Cu precipitates. However, the DA specimen had the highest ultimate tensile strength and elongation owing to the considerable amount of austenite phase and associated transformation induced plasticity effect.

AZ31/Mg3Y composites with a layer thickness of 100–200 μm were fabricated by accumulated rolling bonding (ARB), which was followed by diffusion annealing at 300 °C for 0–32 h. An interface layer, containing numerous Al-Y precipitates, is formed in the Mg3Y layer that is adjacent to the interface as a result of Al diffusing from the AZ31 layers into the Mg3Y layers. The thickness of the interface layer gets increased and more precipitates are formed in the interface layer with the extension of the annealing time. The microhardness of the AZ31 and Mg3Y layer decreases firstly and then reaches a stable value, while the microhardness of the interface layer increases gradually with the extension of the annealing time. The AZ31/Mg3Y composites exhibit equivalent strength but increased ductility after diffusion annealing, in comparison to the as-rolled AZ31/Mg3Y composite. In addition, the AZ31/Mg3Y composites after annealing always present higher strength and ductility than AZ31/AZ31 composite, which was fabricated by the same process as that for the AZ31/Mg3Y composites. Hetero-deformation induced strengthening also plays an important role in the excellent strength and ductility of the annealed AZ31/Mg3Y composite. This study can provide a direction for improving the plasticity and strength of magnesium alloys synergistically.

Superplastic forming is a practical method to manufacture complex-shaped parts of titanium alloys with large deformation. Laminated parts of dissimilar titanium alloys fabricated by superplastic forming can achieve excellent performance by combining the advantages of components. This work displays the superplastic tension behavior and microstructural evolution of dissimilar TC4/SP700 laminate prepared by the diffusion bonding process. Two titanium alloys can achieve metallurgical bonding at parameters of 800 ℃/1 h/5 MPa. Except for dynamic recrystallization and grain growth behaviors upon superplastic tension, stress-induced phase transformation plays an important role in α to β phase transformation apart from the elevated temperature. The superplastic deformation can be attributed to the grain boundary sliding accommodated multiplex motion of dislocations. In addition, the retained strengths of all dissimilar TC4/SP700 laminates after superplastic deformation with different strain rates and temperatures range from 807 to 890 MPa.

Effect of direct aging of 170 °C on corrosion behavior of laser powder bed fused AlSi10Mg (LPBF-AlSi10Mg) was studied by microstructure analysis, electrochemical analysis and X-ray photoelectron spectrometer. The results show that direct aging of 170 °C has little effect on melt pool and Si cellular structure, but promotes the precipitation of nano-Si particles and releases the residual stress. With increasing aging time from 0 to 4 h to 24 h, the corrosion property of the LPBF-AlSi10Mg is deteriorated, which is evidenced by increased corrosion current density and decreased pitting potential and polarization resistance. With increasing the aging time, the thickness of the oxide film formed on surface of the LPBF-AlSi10Mg increases. The Si content of the oxide film of the sample aging for 4 h is the lowest, 9.42 at.%, and it is the highest, 18.62 at.%, for the sample aging for 24 h. The electrochemical noise analysis reveals that the middle-frequency contribution of the Hilbert spectrum is responsible for the deteriorated corrosion performance, which corresponds to metastable pitting initiated by nano-Si particles.

Proper matching of cold-rolled deformation and low-temperature short-term aging can simultaneously enhance the strength and ductility of the lean duplex stainless steel. To investigate this, the microstructure evolution of cold-rolled and aging steels was observed by using scanning electron microscopy, transmission electron microscopy and electron backscattered diffraction. Additionally, the phase volume fraction was measured using X-ray diffraction. In this study, it was observed that the elongation of 21Cr lean duplex stainless steel significantly increased to 16.7% after undergoing moderate cold deformation (~ 40% reduction) and subsequent aging treatment at 550 °C for 30 min. Remarkably, the material still maintained a high yield strength of 1045 MPa. Such an excellent mechanical property was attributed to a unique microstructure combination of fine α'-martensite, twins, coarsened austenite resulting from partial martensite reverse transformation, and two-phase fine layered structure. The result of this study may open up new horizons for the alloy development in order to overcome the low ductility of cold-rolled high-strength lean duplex stainless steel.