碳酸锂溶液封闭处理对阳极氧化AA2099-T83合金耐蚀性能的影响

为开发一种新型铝锂合金表面处理技术,将经酒石酸−硫酸阳极氧化后的AA2099-T83合金浸泡在不同温度−浓度组合的碳酸锂(Li_(2)CO_(3))溶液中进行后处理。结果表明:经过Li_(2)CO_(3)溶液处理后,阳极氧化合金的耐蚀性能显著提高(耐中性盐雾试验长达1300 h)。此外,高温/低浓度和低温/高浓度组合的封孔过程明显不同,在高温模式下阳极氧化膜仅部分封孔,而在低温模式下阳极氧化膜的封孔更加完全。封孔处理合金的高耐腐蚀性主要归因于在阳极氧化膜表面和内部形成的封孔产物(即Li−Al−LDH和/或勃姆石)对腐蚀介质的阻隔作用。

Microstructural characterization of Inconel 718 alloy after pulsed laser surface treatment at different powers

An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers（100, 50 and 25 W）. Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone（MZ）, densities of low angle boundaries（LABs） are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.

Erosion behavior of a ship propeller material of QAl9-4 alloy

The erosion behavior of a QA19-4 alloy as a ship propeller material was investigated.The effects of the solution,the impact angles and the sand content were considered.The test results demonstrate that the mass loss of the alloy in 3.5 wt%NaCl solution is 1.35 times that in tap water,due to the corrosive effect of Cl^(-).The mass loss of the alloy increases as the impact angle increases up to~30°and consequently decreases as the impact angle increases.Also,this feature is typical for the ductile metal behavior.At the impact angle of 0°,this feature is associated with the predominant erosion mechanisms,such as shallow plowing and surface fatigue;at 30°,this feature is micro-cutting,deep plowing and surface fatigue;and at 45°,it becomes indentation accompanied by extruded lips.The mass loss and surface roughness of the alloy increase as the sand content increases under the testing conditions.

Hybrid machine learning and microstructure-based approach for modeling relationship between microstructure and hardness of AA2099 Al−Li alloy

A hybrid approach combining machine learning and microstructure analysis was proposed to investigate the relationship between microstructure and hardness of AA2099 Al−Li alloy through nano-indentation,X-ray diffraction(XRD)and electron backscatter diffraction(EBSD)technologies.Random forest regression(RFR)model was employed to predict hardness based on microstructural features and uncover influential factors and their rankings.The results show that the increased hardness correlates with a smaller distance from indentation to grain boundary(D_(dis))or a shorter minimum grain axis(D_(min)),a lower Schmidt factor in friction stir weld direction(SF_(FD)),and higher sine values of the angle between{111}slip plane and surface(sinθ_(min)).D_(dis) and D_(min) emerge as pivotal determinants in hardness prediction.High-angle grain boundaries imped dislocation slip,thereby increasing hardness.Crystallographic orientation also significantly influences hardness,especially in the presence of T_(1) phases along{111}Al habit planes.This effect is attributable to the variation in encountered T_(1) variants during indenter loading.Consequently,the importance ranking of microstructural features shifts depending on T_(1) phase abundance:in samples with limited T_(1) phases,D_(dis) or D_(min)>SF_(FD)>sinθ_(min),while in samples with abundant T_(1) phases,D_(dis) or D_(min)>sinθ_(min)>SF_(FD).

Synergistic effect of chloride ion and albumin on the corrosion of pure magnesium

In this work, we report on synergistic effect of chloride ion and albumin on the corrosion of pure magnesium through corrosion tests. We show that the adsorption of albumin mainly affects the anodic polarization behavior of pure magnesium in NaCl solution. Low concentration of albumin enhances the reaction reactivity of pure magnesium and the initial evolvement of hydrogen at the initial immersion time. Addition of I glL albumin provides limited corrosion control for pure magnesium in NaCl solution. In comparison with low concentration albumin, addition of 10 g/L albumin can effectively inhibit the further dissolution of pure magnesium in test solutions with NaCI concentration of 0.2-0.8 wt. %, but this effect lowers gradually with increasing the concentration of chloride ion.

EBSD Study of Microstructural and Textural Changes of Hot-Rolled Ti–6Al–4V Sheet After Annealing at 800 ℃

In this paper, electron backscatter diffraction and various other characterization and analysis techniques mclucilng X-raydiffraction, electron channeling contrast imaging and energy-dispersive spectrometry were jointly employed to investigatemicrostructural and textural changes of a hot-rolled Ti-6A1-4V （TC4） sheet after annealing at 800 ℃ for 5 h. In addition,the hardness variation induced by the annealing treatment is rationalized based on revealed microstructural and texturalcharacteristics. Results show that the TC4 sheet presents a typical dual-phase （α＋β） microstructure, with α-Ti as themajor phase and short-rod-shaped β-Ti （minority） uniformly distributed throughout the α matrix. Most of α grains cor-respond to the un-recrystallized structures with a typical rolling texture （c//TD and 〈11-20〉//ND） and dense low angleboundaries （LABs）. After the annealing, the stored energy in the as-received specimen is significantly reduced, along withgreatly decreased LABs density. Also, the annealing allows recrystallization and grain growth to occur, leading toweakening of the initial texture. Furthermore, the water quenching immediately after the annealing triggers martensitictransformation, which makes the high-temperature β phases be transformed into submicron α plates. The hardness of theannealed specimen is 320.5 HV, lower than that （367.0 HV） of the as-received specimen, which could be attributed toreduced LABs, grain growth and weakened texture. Nevertheless, the hardening effect from the fine martensitic platescould help to suppress a drastic hardness drop.