Plasma Electrolytic Oxidation (PEO) technology enables the in-situ growth of metal oxide-based ceramic coatings on the surfaces of metals and alloys such as aluminum, magnesium, titanium, and zirconium. In this work, a ceramic coating with uniform color and superior performance was successfully fabricated on H13 steel via a hybrid voltage-current control mode (step-up constant voltage followed by constant current) in an electrolyte containing 8 g/L NaAlO₂ and 2 g/L (NaPO₃)₆. The morphology, structure and chemical composition of the coatings were characterized using SEM, EDS, and XRD. The results indicated that after 40 min of treatment using the hybrid voltage-current control mode in the aluminate electrolyte, the thickness of the PEO coating reached 160.5 μm, and all coatings were predominantly composed of Fe3O4, Al2O3, and FeAl2O4 phases. The average hardness of the coating prepared under the hybrid voltage-current control mode for 30 min was 1249.22 HV1, while that of the substrate was only 186.02 HV1. Dry sliding wear tests demonstrated that the coatings prepared under the hybrid voltage-current control mode for 30 min exhibited excellent wear resistance. Under a load of 10 N, the coating demonstrated an ultra-low wear rate of 2.35 × 10⁻⁶ mm³•N⁻¹•m⁻¹ after 1800 s of dry sliding against a high-hardenability SiMnGCr15 steel ball. Adhesion tests revealed that the PEO coating prepared for 30 min achieved a coating-substrate adhesion strength as high as 39.24 MPa. The superior wear resistance of this coating is attributed to its good adhesion, dense microstructure, highly wear-resistant phase composition, and ultra-high surface hardness.

H13 steel is extensively utilized in the production of various forming dies due to its high strength, hardness, and toughness. However, due to its limited wear and corrosion resistance, the service life of the material is significantly reduced. In this work, plasma electrolytic oxidation (PEO) electrolytes consisting of Na2SiO3, NaAlO2, (NaPO3)6 and NaH2PO4 were selected. The coating formation condition of H13 steel treated with PEO in different electrolytes was investigated to determine the optimal electrolyte composition, and which was found to be 8 g/L NaAlO2 + 2 g/L (NaPO3)6. Furthermore, the morphology and chemical composition of the PEO coatings were investigated using SEM, EDS and X-ray diffraction (XRD). The results showed that the PEO coatings prepared in the aluminate electrolyte were mainly composed of Fe3O4, Al2O3 and FeAl2O4 phases. The average hardness of the coating prepared at 680 V was 787.83 HV1, which showed excellent wear resistance without any wear being observed after 1800 s wear test again G-Cr15 steel ball under a load of 10 N. Tafel curve results revealed that the corrosion potential of the PEO coating prepared at 680 V was -0.672, and the corresponding corrosion current density was 4.85 x 10- 8 A center dot cm- 2. The PEO treatment significantly improved the corrosion resistance of the material compared to H13 steel substrates.

This study explores the effects of intermediate annealing (IA) on the microstructure, texture, bendability, and deep drawability of an Al-Mg-Si alloy. It is found that that IA induces particle precipitation and static softening, leading to increases of the average size, number density, and volume fraction of both coarse and fine particles, along with a weakening of rolling texture. These effects become more pronounced with rising IA temperature. The changes in particle distribution and texture significantly influence the final grain size and texture, thereby affecting both bendability and deep drawability. The bendability of the IA-treated sheets is improved as the IA temperature increases, due to the changes in texture components from P and CubeND to Cube. Compared to the Non-IA sheet (dominated by Cube texture), the sheet treated with IA at 430 degrees C exhibits better bendability due to refined grain sizes. Introducing IA or increasing IA temperature improves the deep drawability by weakening the texture intensity of the T4P sheets. These results suggest that achieving both high bendability and deep drawability in Al-Mg-Si alloy is feasible by optimizing IA temperature. This study provides an experimental basis for the possibility of broader applications of Al-Mg-Si alloys in the automotive industry.

The influence of crystallographic textures, which was correlated to intermediate annealing (IA) after hot-rolling, on the hemming performance of Al–Mg–Si alloy sheets was investigated in the present paper. Cube (001 < 100 >) texture is developed after IA and is partially retained after cold-rolling, becoming increasingly pronounced as the IA temperature rises, with the particle-stimulated nucleation (PSN) texture predominating in T4P sheets. In contrast, the T4P sheet without prior IA develops a strong Cube texture, but the clustering of Cube-oriented grains leads to deformation incompatibility with surrounding grains. Consequently, the hemming performance of T4P sheet without prior IA is inferior to that of IA-treated sheets. The hemming performance is improved by IA treatment due to the development of the CubeND ( 22° ND-rotated Cube, 001 < 310 >) orientation induced by the PSN effect. And the hemming performance can be further improved by increasing IA temperature, due to coarsening of Mg2Si particles and the increase of effective PSN particles which lead to the increase of volume fraction of CubeND orientation in T4P sheets.

An amorphous SiO2 ceramic coating with a thickness of ∼72 μm is prepared within 13 min in organo-silicon electrolyte, which is stable in strong acid solutions, reducing corrosion current density of 6061 aluminum alloy by 3 orders of magnitude. With the aim to reveal influence of the electrolyte concentration, NaOH content and additive (NaPO3)6 on microstructure and corrosion resistance of the coatings, SEM/EDS, XRD, electrochemical tests were used to characterize their thickness, surface and cross-sectional morphology and structure, and corrosion performance prepared by using different electrolytes under the same electric control parameters. The results show that they significantly affect the surface morphology, structure and corrosion resistance of the coatings. Dilution of the electrolyte results in a significant decrease in coating thickness and surface porosity, reduction of NaOH content leads to coating thinning, increased porosity but reduced pore size. Coatings with lower porosity or smaller pore sizes are more effective in resisting corrosive media penetration for long term immersion. Whereas, the additive (NaPO3)6 promotes coating thickening, widening of the transition layer, which helpfully improves the corrosion resistance of the coating.

An amorphous silica ceramic coating with thicknesses exceeding 100 mu m (adjustable thickness) was prepared on 6061 aluminum alloy by plasma electrolytic oxidation in organosilicon electrolyte. To investigate its formation process and structural characteristics, the digital microscope system, SEM, X-ray diffractometer and microhardness tester were used to characterize morphology, structure and hardness at different voltages and times. The results show that it thickens rapidly after the voltage is raised to 480-500 V, and its surface begins to roughen and the micropores appear to enlarge. In organosilicon electrolyte, unlike conventional electrolytes, the coarse Al-Fe-Si second phase particles in the matrix do not negatively affect the PEO treatment. The produced coatings increase the surface hardness of 6061 aluminum alloy by more than 6 times and are stable in common acid solutions such as HCl and HNO3. Furthermore, the energy consumption rate of PEO treatment can be significantly reduced to 0.24-0.31 kJ cm-2 mu m- 1. The potentiodynamic polarization curves measured in 1 mol L-1 HCl solution show that the ceramic coating can reduce the corrosion current density of 6061 aluminum alloy from 3.74 x 10-2 A cm- 2 to 2.24 x 10-6 A cm- 2. And its corrosion resistance can be further improved by adding a 2nd low-voltage PEO treatment.

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 mu m, 83.2 mu m and 193.3 mu m increased the surface hardness of 6061 aluminium alloy by 6-8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L- 1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Plasma electrolytic oxidation (PEO) was performed on 6061 aluminum alloy in organosilicon electrolyte using a stepwise constant potential control method for 23 min. The resulting coating was a sponge-like structured amorphous silica ceramic with a thickness of about 130 mu m. Its exceptional wear resistance was attributed to the high hardness of the silica ceramic and the low elastic modulus of the sponge-like structure. The corrosion resistance was enhanced by a dense layer of approximately 2 mu m between the coating and the substrate. Impressively, the indentation depth of the PEO coating during nano-indentation tests was only 50-60% of that of 6061 aluminium alloy under varying loads, while the recovery depth of the PEO coating after unloading was 2.5-3.1 times greater than that of 6061 aluminium alloy. Due to its special composition and structure, the PEO coating caused serious wear to the high hardness Si3N4 friction balls during the friction and wear test. In the electrochemical tests, the coating reduced the corrosion current density from 1.056 x 10(-5)A center dot cm(-2) to 1.239 x 10(-7)A center dot cm(-2), while extending the passivation region from 0.322 V to 1.032 V.

A zeolite film was prepared by hydrothermal synthesis on the surface of 7204 aluminum alloy pretreated with 3-aminopropyltriethoxysilane（APTES）. The effect of silane pretreatment on morphology and corrosion resistance of zeolite film was studied with the zeolite film synthesized directly on the surface of 7204 aluminum alloy as a control. The scanning electron microscopy（SEM） observation indicated that the silane pretreatment facilitated the nucleation of zeolite film,resulting in a reduction of zeolite particle size. The results of polarization curve measurement and electrochemical impedance spectroscopy（EIS） in 3.5% NaCl solution showed that the silane/zeolite film exhibited superior long-term corrosion resistance to the pure zeolite film, which was attributed to the enhancement of the gel layer formation in zeolite film through the silane pretreatment.

Three different processes (non-3-aminopropyltriethoxysilane (APTES) pretreatment followed by one-step hydrothermal synthesis, APTES pretreatment followed by one-step hydrothermal synthesis, APTES pretreatment followed by two-step hydrothermal synthesis) were used to synthesize an MFI zeolite coating on mechanically polished H13 steel to improve corrosion resistance. The coatings synthesized by the different processes were remarkably different in terms of zeolite particle size, thickness, density, and corrosion resistance. In the case of the MFI zeolite coating synthesized on non-APTES-pretreated H13 steel, a non-dense gel layer and poorly intergrown zeolite particle layer lowered adhesion strength and corrosion ability, whereas the presence of the APTES film increased the density of the gel layer. Consequently, it showed better adhesion strength, and corrosion resistance with a lower corrosion current density (Icorr) and higher impedance value at 0.01 Hz. The adhesion strength and corrosion resistance of the MFI zeolite coating was further enhanced by two-step hydrothermal synthesis because the gel layer became denser and thicker in the early stages of secondary synthesis. The molten immersion test also indicated that the MFI zeolite coating had a high corrosion resistance in molten aluminum.

The influence of silane pretreatment with five different volume ratios (100/0, 75/25, 50/50, 25/75, and 0/100) of 3-aminopropyltriethoxysilane (APTES)/tetraethylorthosilicate (TEOS) on microstructure and corrosion resistance of the hydrothermal synthesized zeolite coatings on the H13 steel substrates was investigated. The surface of the zeolite coatings on the 100/0, 75/25, and 50/50 mixture of the APTES/TEOS pretreated substrates was composed of intergrown rectangular particles. Additionally, pores were observed. A 25/75 mixture of APTES/TEOS pretreatment smoothed the edges and angles of zeolite particles with gel-like materials filled in the pores. In pure TEOS pretreatment, microcracks, and much gel-like materials were observed on the zeolite coating. The electrochemical test revealed that the zeolite coating on a 50/50 mixture of the APTES/TEOS pretreated substrate exhibited the highest corrosion resistance in 3.5 wt-% NaCl solution. This was because a 50/50 mixture of APTES/TEOS pretreatment advantageously promoted development of a dense and thick gel layer, which enhanced the intergrowth of zeolite particles.

采用单轴恒应力蠕变试验、电子背散射衍射(EBSD)和透射电子显微镜(TEM)技术等实验手段,研究了Al-Cu-Li合金厚板的不均匀组织特征对其蠕变时效成形过程的影响.结果表明:厚向不均匀组织的差异性表现出明显不同的蠕变变形行为,靠近中心层的特征组织具有更高的蠕变量和更快的初始蠕变速率;厚板特征组织的晶粒尺寸与蠕变变形之间无确定的相关性,而位错运动是影响蠕变量的主要因素;晶粒尺寸在蠕变时效前后变化微小,但蠕变时效后小角度晶界比例存在不同程度的提高.此外,厚板不同特征组织会影响蠕变时效过程中强化相T1的析出行为,靠近中心层的特征组织在蠕变过程中会形成更多的位错缠结,促使T1相大量析出和致密分布.

A zeolite coating was synthesized on a nitrocarburized H13 steel substrate to improve its wear and corrosion resistance using a two-step hydrothermal synthesis approach. The wear test showed that compared with the nitrocarburized H13 substrate, the zeolite-coated sample offered significantly better wear resistance with slightly lower mean coefficient of friction (COF), narrower and shallower wear profiles, and an approximately half wear rate. During the wear process, the protruding corners and edges of the zeolite particles gradually abraded into smooth areas. The wear mechanism of the zeolite-coated H13 sample against the GCr15 grinding ball included the abrasive wear of zeolite particles, formation of a transfer layer, surface oxidation of the wear debris through plastic deformation, and peeling off of the local zeolite particles. Electrochemical and immersion tests showed that the synthesized zeolite coating significantly enhances the corrosion resistance of the steel.

为提高H13模具钢氮碳共渗后表面的耐蚀性,通过一次水热合成法在其表面制备了沸石涂层.采用扫描电子显微镜(SEM)和能谱仪(EDS)分别表征了沸石涂层的结构特征以及元素组成.采用Tafel极化曲线测试、电化学阻抗谱测量以及3.5％NaCl溶液室温浸泡实验考察了沸石涂层的耐蚀性.结果表明,采用一次水热合成法制备的涂层由交联生长的沸石颗粒构成,其厚度约为18μm.在3.5％NaCl溶液中,其腐蚀电流密度比H13氮碳共渗基体低2个数量级,浸泡840 h后的低频阻抗模值比没有浸泡时下降了约一个数量级,但仍比氮碳共渗基体高1.5倍.在3.5％NaCl溶液中浸泡1800 h后,沸石涂层在微观上出现了大量的腐蚀产物,表明它已逐渐失效.

For micro-arc oxidation (MAO) coating on aluminium alloys, the corrosion medium can permeate through the microvoids and cracks in it to decrease its corrosion resistance. In this study, a method of two-steps hydrothermal synthesis has been developed to prepare a composite coating by the synthesis of zeolite film on MAO-coated Al alloy substrate. The zeolite crystals are well intergrown into a continuous film and the micro defects in the MAO coating are sealed. This kind of composite coating can provide excellent long-term corrosion protection to Al alloy substrate. The effect of the first-step hydrothermal synthesis on the microstructure of the MAO coating and zeolite film has been studied.

采用160 g/L硫酸溶液在17°C下对7N01铝合金阳极氧化30 min,氧化电压分别选取14、15、16、17和18 V.用扫描电镜观察所得阳极氧化膜的形貌,用能谱仪和电化学测量分析了它的成分、厚度和耐蚀性.结果表明,7N01铝合金经过不同电压下的阳极氧化处理后,表面均能形成凹凸不平并有孔洞的阳极氧化膜,电压为17 V时所制膜层致密、均匀,厚度约为7.6μm,耐蚀性最佳,在3.5％NaCl溶液中浸泡1440 h后没有明显的腐蚀.

分别采用硅酸盐与磷酸盐-硅酸盐复合电解液在 7N01 铝合金表面制备了微弧氧化膜(MAO).采用扫描电子显微镜观察它们的微观形貌,用X射线衍射仪分析了它们的物相,并用极化曲线测量、电化学阻抗谱和盐水浸泡试验考察了它们的防腐蚀性能.结果表明,两种体系所得微弧氧化膜均主要由 α-Al2O3和 γ-Al2O3相组成.与硅酸盐体系所得膜层相比,磷酸盐-硅酸盐复合体系所得膜层更加致密,防腐蚀作用更好.

采用一次水热合成法在H13模具钢表面制备沸石涂层.采用扫描电子显微镜、能谱仪和X射线衍射仪表征沸石涂层的结构和成分,采用极化曲线和交流阻抗谱分析涂层的耐蚀性能.结果表明,制备的沸石涂层为MFI结构,涂层连续致密.3.5wt％盐水中的电化学测试结果表明,沸石涂层覆盖的H13模具钢腐蚀电流密度比未处理样品低2个数量级,浸泡276 h时的阻抗测中低频阻抗比未处理样品高出4个数量级.在3.5wt％的盐水浸泡696 h后的宏观形貌表明沸石涂层样品无明显腐蚀现象,说明沸石涂层能显著提高H13模具钢的耐蚀性能.

The effects of pre-stretching on creep behavior, mechanical properties and microstructure during the creep aging process of Al-Cu-Li alloy were investigated. AA2195 was taken as the representative of Al-Cu-Li alloys. It is found that the total creep strain and strength property of creep aged AA2195 specimens can be improved through effective pre-stretching. Unlike with artificial aging, yield strength increased increasing by 47%. The TEM images show that the constitution of aging precipitates in the creep-aged specimens are obviously changed by pre-stretching. Precipitates in the 2% pre-stretched specimen are mainly composed of T1 phase, while a great amount of θ’ phase accompanied with a few T1 phase were found in the non-pre-stretched specimen. Moreover, pre-stretching introduces many dislocations which benefit the creep deformation, but the increasing dislocation density also accelerates the nucleation and growth of the precipitates as well. The premature T1 phase has a great blocking effect to the dislocation motion, creating a lower decrease rate but a longer duration in the early creep stage. Except for the initial dislocations, the dislocation motion in the creep aging process is also a favorable factor to precipitate the T1 phase.

A MFI zeolite coating was prepared on friction stir processed 6A01 aluminum alloy (coded as FS6A01) by hydrothermal synthesis in a solution comprising tetrapropylammonium hydroxide (TPAOH), NaOH, tetraethyl orthosilicate (TEOS), and H2O with a molar ratio of 0.16:0.64:1.00:92.00 at temperature 180 °C for 24 h. Its surface and cross-section morphologies of the MFI zeolite coating were observed by scanning electron microscopy (SEM), elemental composition and phase structure were analyzed by energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD), and corrosion resistance was evaluated by polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the zeolite coating prepared on FS6A01 substrate is intact and compact with a thickness of 5 μm. The corrosion current density of the FS6A01/MFI zeolite coating was 3 orders of magnitude lower than that of FS6A01 substrate. The impedance at low frequency of the FS6A01/MFI zeolite coating after being immersed in 3.5% NaCl solution for 984 hours was decreased by about one order of magnitude as compared with that immersed for 1 hour, but was still higher than that of the FS6A01 substrate after being immersed for 15 min.