Lin Xiang

Using additive friction stir deposition (AFSD), the poor weldability of 1045 steel can be solved, facilitating the efficient and high-performance additive manufacturing of its components. This study selected spherical 1045 steel powder and investigated key factors influencing mechanical properties, including deposition temperature, tool rotational rate, and axial force. The results showed that dynamic recrystallization (DRX) occurred in AFSD 1045 steel, which produced randomly oriented fine equiaxed grains with a size range of 1–3 µm and was sensitive to changes in tool rotational rate and axial force. The AFSD 1045 steel, with a maximum surface hardness of 477.2 HV, ultimate tensile strength of 1061.9–1172.3 MPa, and elongation of 8.6–19.0%, has superior overall mechanical properties compared with other forming processes. Moreover, by analyzing tensile fracture morphology, geometrically necessary dislocation (GND) density, and coincidence site lattice (CSL) boundary distribution characteristics, the strengthening mechanism in AFSD 1045 steel was discussed. The research findings serve as a reference for optimizing the AFSD process for 1045 steel and supply a new alternative for joining and manufacturing this material.

In this study, we employed the first-principles method based on density functional theory to calculate the elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and density of states for both cubic and tetragonal phases of Pb(Zr_xTi_1−x)O₃. The structural model of Pb(Zr_xTi_1−x)O₃ was established using the virtual crystal approximation (VCA). Our results demonstrate that the VCA-calculated properties are in excellent agreement with other theoretical predictions and experimental data. As the Zr content increases, the lattice constants of both cubic and tetragonal Pb(Zr_xTi_1−x)O₃ increase, while the c/a ratio initially decreases and subsequently increases. Both cubic and tetragonal Pb(Zr_xTi_1−x)O₃ satisfy the Born stability criteria, indicating mechanical stability. For the cubic phase, the elastic constants, bulk modulus, and shear modulus decrease with increasing Zr content. In contrast, for the tetragonal phase, the elastic and shear moduli exhibit a non-monotonic trend, peaking at a Zr content of 0.5, where Pb(Zr_0.5Ti_0.5)O₃ demonstrates superior mechanical properties. A comparative analysis reveals that as Zr content increases, the cubic phase exhibits enhanced structural resilience, greater electronic structure stability, and increased anisotropy. These characteristics make cubic Pb(Zr_xTi_1−x)O₃ more suitable for advanced manufacturing techniques such as additive manufacturing, offering enhanced design flexibility for ferroelectric materials.

This study aims to examine the variation in corrosion characteristics and tensile properties of WE43 magnesium alloy in an actual marine atmospheric environment by means of outdoor exposure tests. The macroscopic corrosion morphology, microstructure, and tensile properties were analyzed. The results indicated that WE43 alloy will corrode rapidly during exposure under marine atmospheric environmental conditions, resulting in a loose and porous Mg(OH)₂ layer on the surface. The Mg matrix was mainly consumed as an anode, leading to the occurrence of corrosion pits. With the increase in exposure time, both the tensile strength and plasticity of WE43 alloy gradually deteriorated. After exposure for six months, the elongation and area reduction were significantly reduced, with a reduction ratio of more than 50%. After 18 months of exposure, the ultimate strength of the alloy decreased from 359 MPa to 300 MPa. According to an analysis of fractures in the alloy, the corrosion pits on the sample surface were the main reason for the decrease in tensile properties.

This study aimed to investigate the impact of corrosion on the microstructure and tensile properties of 7075 high-strength alloy. It involved outdoor exposure tests in an actual marine atmospheric environment in Wanning, Hainan Province. The results showed that the 7075 alloy was corroded rapidly in the marine atmospheric environment, and corrosion pits and intergranular cracks were generated. The intergranular cracks were extended along the grain boundary during corrosion, leading to the exfoliation of the matrix. The cause for the intergranular corrosion was discussed based on the microstructure characteristics of 7075 alloy. The tensile properties of the 7075 alloy gradually deteriorated with the increase of exposure time in the marine atmospheric environment. The ultimate strength and elongation were decreased by about 3.2% and 58.3%, respectively, after 12 months of outdoor exposure.

This work analyzed changes in the corrosion morphology and mechanical performance of 7085 aluminum alloy after outdoor exposures for different times in a humid and hot marine atmospheric environment. After one month of exposure, a pronounced corrosion of the alloy was observed. The corrosion product was mainly Al(OH)₃, and the corrosion features were mainly pitting corrosion and intergranular corrosion (IGC). With the exposure time extended from 6 months to 12 months, the IGC depth increased from 114 μm to 190 μm. After a 1-year outdoor exposure in a humid and hot marine environment, the alloy’s ultimate strength and yield stress remained nearly unchanged, while its elongation and area reduction decreased from the original 6% and 9%, respectively, to 3% and 5%. Moreover, the reasons for IGC and its effect on the mechanical performance was analyzed.

Previous results reported that SiCp (Silicon Carbide particles) particle doping proved to be effective in enhancing the wear performance of WE43 magnesium alloy. In this work, finite element simulation was employed to investigate the effect of SiCp particle shape on the mechanical behaviors of SiCp/WE43 magnesium matrix composites. SiCp particles underwent larger load internally and a smaller plastic deformation under tensile loading, leading to the enhanced strength and stiffness of the composites. Polygonal SiCp particles provided a better enhancement in strength for the composites than round SiCp particles, but the enhancement in stiffness was opposite. Meanwhile, the damage is likely to initiate at the interface between the matrix and particle, at the location of the highest stress concentration. This phenomenon was more prominent in polygonal particle-reinforced composites. These current findings provide a comprehensive understanding of the effect of SiCp particle shape on the mechanical behaviors of magnesium matrix composites.

The objective of this work was to study the corrosion behavior of 2xxx aluminum alloys in the marine environment and the degradation of mechanical properties caused by corrosion as well as to provide support for the lightweight design of marine equipment. The corrosion characteristics of 2297-T8 and 2195-T8 were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) at 3, 6, 9, and 12 months of exposure, and the mechanical properties were obtained via uniaxial tensile testing. The results of the study showed the following: (1) With an increase in the exposure time, the corrosion products on the surface of 2297-T8 gradually increase, and the corrosion products on the surface of 2195-T8 accumulate rapidly. (2) The results of EDS show that the corrosion products of 2297 are mainly Al oxides and that those of 2195 are composed of Al, Fe, Mn, Si, etc. (3) Through the corrosion pit diameter, corrosion pit depth, and corrosion mass reduction rate surface, the trend of an increasing average radius of the corrosion pits and the corrosion mass reduction rate surface varies linearly, and the average depth of the corrosion pits increases dramatically after 9 months of exposure time. (4) According to the mechanical properties of the study surface, in a marine atmosphere, the degradation of 2297-T8 ductility is higher than that of 2195-T8, while the degradation of the yield stress is lower than that of 2195-T8.

The effect of a chromium (Cr) transition layer on the hot-salt corrosion behavior of an AlSi alloy coating was studied. Hot-salt corrosion experiments were performed at 650 °C and corrosion kinetic curves were plotted. The weight gain of the AlSi-coated samples increased to 0.89 mg/cm² at 100 h and then decreased steadily to 0.77 mg/cm² at 200 h. The weight of the AlSi-coated samples with the addition of a Cr transition layer increased immediately to 0.79 mg/cm² at 20 h and then gradually increased to 0.85 mg/cm² at 200 h. This Cr diffusion promoted the preferential creation of an Al₂O₃ layer, which effectively hindered the upward diffusion of Fe and also resulted in the production of a Cr₂O₃-SiO₂ layer, which impeded the multi-scale salt mixture’s penetration. The Cr diffusion also caused a notable seal-healing effect, which healed the micro-pores. These oxidation and degradation reactions were considerably repressed by the high barrier properties of these oxide layers and the dense surface, resulting in the increased hot-salt corrosion resistance of the AlSi alloy coating. The current findings provide a feasible strategy for the design of a diffusion barrier layer of a thermal protective coating on martensitic stainless steel.

Detailed tests and characterizations were used to investigate the corrosion degradation behaviors of Ti6Al4V alloys in simulated marine environments. These alloys suffered from very slight pitting and a miniscule weight loss of 0.018 mg/cm² during the 50 cycle salt spray exposure but experienced significant oxygen erosion in the high-temperature oxidation test, resulting in a high weight gain of 2.657 mg/cm² at 400 h. The oxidation and degradation reactions simultaneously occurred during the high-temperature hot salt test. The chlorine (Cl₂) induced by the eutectic reaction of the mixed salts accelerated the degradation of the substrate and led to a higher weight gain of 4.265 mg/cm² at 400 h. In contrast, this alloy suffered from severe corrosion damage during the high-temperature hot salt–water vapor synergy test. The degradation of TiO₂, Al₂O₃, and V₂O₅ was aggravated by the synergistic action of chlorine salt and water. The reaction forming hydrochloric acid (HCl) further degraded the matrix metal and consequently led to a high weight loss of 16.358 mg/cm² at 400 h. These current findings provide a comprehensive understanding for the degradation mechanisms of Ti alloys in these specific marine environments.

Actual marine atmospheric pre-corrosion behavior and its effect on the fatigue performance of 7075-T73 aluminum alloy were studied by means of marine atmospheric outdoor exposure testing and fatigue testing. The surface and cross-sectional microstructures of aluminum alloy specimens after different numbers of days of exposure were analyzed. Localized pitting, and intergranular and exfoliation corrosion occurred during the outdoor exposure of aluminum alloy specimens in a marine atmosphere. The degree of severity of atmospheric corrosion increased with increasing duration of exposure. The effects of Fe-rich constituent particles (Al₂₃CuFe₄) and grain boundary precipitates (MgZn₂) on the marine atmospheric corrosion behavior were discussed. In addition, when the exposure time was increased from 0 days to 15 days, the average fatigue life of aluminum alloy specimens decreased dramatically from about 125.16 × 10⁴ cycles to 16.58 × 10⁴ cycles. As the exposure time was further increased to 180 days, the average fatigue life slowly decreased to about 6.21 × 10⁴ cycles. The fatigue fracture characteristics and the effect mechanism of marine atmospheric pre-corrosion on the fatigue life of 7075-T73 aluminum alloy were also analyzed.