扫描电子束铝合金表面处理温度场分析与实验验证

根据扫描电子束焊机的实际工作环境,建立了扫描电子束铝合金表面处理温度场三维有限元分析模型,分析了试样经电子束照射后表面熔池的形态及组织变化,分析过程中,考虑了试样表面的热辐射和材料的相变,并用实验验证了仿真结果。讨论了束流、束斑直径和扫描半径对扫描电子束表面处理温度场的影响。结果表明:在其它参数不变的情况下,随着束流的增大,试样表面的最高温度基本上呈线性增高,熔池的宽度和深度也有所增大;随着束斑直径的增加,试样表面的最高温度呈线性下降,熔池的深度也略有减小,而宽度则快速地增大;随着扫描半径的增加,最高温度、熔池的宽度和深度均急剧下降。

以需求为导向的应用型课堂本科教学改革与建设——以铝合金表面处理技术课程为例

当代大学生面临诸多就业问题,不但就业竞争大,而且就业要求高,很多企业招聘都是面向"具有实战技术或技能"的毕业生。由此对当代大学生的实践运用能力提出了更高的要求,对于应用型本科而言,就意味着需要改变以往陈旧的教学模式,强化实践运用,真正将理论知识运用于实践,从而培养出符合社会需要的高素质专业人才。对此,文章分析铝合金表面处理技术课程在教学中存在的问题,并基于以需求为导向的应用型课堂,给出教学改革与建设的意见。

铝合金表面处理工业废渣制备氢氧化铝工艺

研究了以铝合金表面处理工业废渣为原料制备Al（OH）3的工艺,探讨了NaOH浸提Al和H2SO4法沉淀制备Al（OH）3的过程,考察了碱酸浓度及用量、温度、时间等对制备过程的影响,采用正交实验确定了最佳工艺条件,分析了Al（OH）3产品的化学组成、形貌和质量.结果表明,干燥废渣中Al含量为28.7%,以Al（OH）3晶体存在.在加入的NaOH与废渣中Al（OH）3摩尔比为2.88：1、反应温度75℃、时间55 min的最佳浸提条件下,Al浸出率达97.5%.在加入的H2SO4与浸提液中AlO2-摩尔比为（0.95~1.10）：1及pH=5.5的最佳沉淀条件下,Al（OH）3的沉淀收率为89.2%,Al总回收率为87.1%.Al（OH）3产品为无定型白色粉末,粒径约为17μm,纯度达95.5%.

论汽车变速器铝合金壳体与零部件的表面防腐

铝合金壳体和零部件的自身优点是比重小、可加工性好、力学性能优异、导电导热能力强,但其自身形成的氧化膜很难抵抗应用环境的腐蚀,必须通过合理的表面处理方法来提高其耐蚀性能。因此,研究铝合金的防腐性能具有重要意思,文章将介绍几种提高铝合金耐蚀性的表面处理工艺。

铝合金三价铬本色钝化实践

介绍了铝合金三价铬钝化工艺流程和重要工序，分析了钝化液成分及操作条件对钝化工艺的影响。采用三价铬钝化工艺可使铝合金表层的耐蚀性大大提高。

免涂装铝合金轨道车辆研究

阐述免涂装轨道车辆关键技术,包括车体主要结构、车体制造技术及车体外表面表面处理工艺。车体由顶盖、侧墙、地板以及司机室等大部件组成,通过熔化焊及搅拌摩擦焊焊接而成。车体制造完成后,外表面首先进行焊缝整体打磨,然后进行表面拉丝处理。

离子注入改善电接触微动磨损研究

以AgCu10合金为对象 ,研究和探讨了离子注入提高电接触材料的抗氧化和抗磨损性能并改善电接触微动磨损的技术。试验结果表明 ,离子注入后的AgCu10合金大大减少了磨损颗粒的产生 ,降低了磨损过程中产生的金属转移 ,减轻了磨损颗粒的氧化污染 ,从而提高合金表面耐磨损和抗腐蚀性能 。

Preparation of cerium oxide based environment-friendly chemical conversion coating on magnesium alloy with additives

Ce（SO4）2？H2O2 solution was adopted to prepare a chemical conversion coating on AZ91D magnesium alloy.Additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate were applied to improving the coating formation.SEM,EDS,XRD and GIXD were adopted to study the coating morphology,structure and composition,and the potential change curve in the treating solution was recorded to study the coating growth.Sodium dodecyl benzene sulfonate makes a remarkable improvement in the coating compactness,and shortens the time in the second stage of the coating formation from 5 min to 2 min.Compared to Ni（NO3）2,sodium dodecyl benzene sulfonate makes the more remarkable effect on the corrosion resistance improvement,since it can decrease the current density of corrosion from 7.41×10-5 A/cm2 to 2.20×10-5 A/cm2.The additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate can enhance the Ce content from 18.92% to 22.32% and 25.08% in the coating,respectively.The XRD and GIXD results indicated that all the conversion coating formed in different solutions exhibit amorphous structure.

State-of-art on corrosion and protection of magnesium alloys based on patent literatures

The state-of-art of patented technologies for surface treatment of magnesium alloys including chemical conversion electrochemical plating, surface coating, and multiple-step surface treatment technologies was reviewed and analyzed. Some new techniques were introduced. It was found that conversion film technologies account for a large amount of proportion among the patents of surface treatment. These technologies are also the main technologies used in industry. As the structures and service conditions of Mg alloy parts are of variety, a single surface-treatment process can not satisfy all requirements. Combined surface-treatment techniques can meet the needs in different applications. More and more new and environmental friendly techniques were invented. Factors such as capital investment, ease of manufacturing, and coating performances have to be considered when developing a coating technology for the industrial application.

喷丸成形及强化对2024HDT-T351板材疲劳特性的影响

目的获得喷丸成形及喷丸强化工艺对2024HDT-T351板材疲劳特性的影响规律。方法设计了一种不传载的含紧固件单细节结构疲劳品质试验件,各组试验件相同,变化各组的喷丸参数,进行了试验基准组、喷丸强化组和4种不同参数喷丸成形组、4种不同参数喷丸成形后喷丸强化组的疲劳试验。结果通过疲劳试验和数据处理,获得了各组的疲劳性能、细节疲劳额定值和在相应应力水平下的疲劳寿命。试验结果表明,所有组的细节疲劳额定值均高于试验基准组,其中喷丸强化试验组的疲劳性能提高了24%,喷丸成形试验组的疲劳性能提高了9%~13%,喷丸成形后喷丸强化试验组的疲劳性能提高了9%~24%。结论给出了2024HDT-T351板材喷丸成形及强化疲劳分析合金和表面处理系数B。2024HDT-T351铝合金板材经喷丸强化后、经大弹丸喷丸成形后和经大弹丸喷丸成形后喷丸强化,疲劳分析时合金和表面处理系数B可保守取1.2、1.05、1.05。

Effect of fluoride treatment on corrosion behavior of Mg-Ca binary alloy for implant application

The influence of hydrofluoric acid（HF） treatment on the corrosion behavior of the Mg-0.5Ca alloys was investigated by immersion specimen in sodium hydroxide and HF solutions with various concentrations and durations at room temperature.Microstructural evolutions of the specimens were characterized by atomic force microscopy,X-ray diffraction,field-emission scanning electron microscopy.The corrosion resistance was examined through potentiodynamic polarization and immersion test in Kokubo solution.The results revealed that the fluoride treated Mg-0.5Ca alloys produced by immersion in 40% HF provided more uniform,dense and thicker coating layer（12.6 μm） compared with the 35% HF treated specimen.The electrochemical test showed that the corrosion resistance of fluoride treated specimen was 35 times higher compared with the untreated Mg-0.5Ca alloy specimen in Kokubo solution.In vitro degradation rate of the fluoride treated specimens was much lower than untreated Mg-0.5Ca alloy in Kokubo solution.After immersion test the surface of 40% HF treated sample showed a few corrosion dots,while untreated specimens were fully covered by corrosion products and delamination.Fluoride treated Mg-0.5Ca alloy with 40% HF is a promising candidate as biodegradable implants due to its low degradation kinetics and good biocompatibility.

Effect of electrolyte on mechanical properties of AZ31B Mg alloy in electrolytic plasma processing

Coatings on Mg alloys were prepared using NaOH + Na2SiO3 as basic electrolyte containing electrolyte of Na2SiF6 or NaF. EPP treatment was carried out on AZ31 Mg alloys matrix under a hybrid voltage of AC of 200 V combined with DC of 260 V for 30 min. Structural and morphological analyses of ceramic coatings were analyzed by XRD and SEM. Wear and hardness of coatings were measured by pin-on disk test and Vickers hardness test. The coatings formed in Na2SiF6 and NaF electrolytes were mainly composed of MgO and Mg2SiO4. The measured micro-hardness of coating formed in Na2SiF6 electrolyte was found to be over HV 1100, while, coating formed in NaF electrolyte possessed micro-hardness of HV ~900. These results show that the mechanical properties of AZ31 B Mg alloys can be enhanced by the proper selection of electrolyte agent.

A perspective of microplasma oxidation (MPO) and vapor deposition coatings in surface engineering of aluminum alloys

Over the past years, great achievements have been made in the development of coating technologies for surface improvement of aluminum alloys. Despite these achievements, the role in the market strongly depends on the ability of surface coating technology under technical and economic considerations to meet the increased demands for heavy tribological applications of aluminum alloys. Microplasma oxidation (MPO) technology has recently been studied as a novel and effective means to provide thick and hard ceramic coating with improved properties such as excellent load-bearing and wear resistance properties on aluminum alloys. The present work covers the evaluation of the performances of current single and duplex coatings combining MPO, physical vapor deposition (PVD), and plasma assisted chemical vapor deposition (PACVD) coatings on aluminum alloys. It suggests that the MPO coating is a promising candidate for design engineers to apply aluminum alloys to heavy load-bearing applications. The prospective future for the research on MPO coatings is introduced as well.

Formation mechanism and wear behavior of gradient nanostructured Inconel 625 alloy

The formation mechanism and wear behavior of a gradient nanostructured(GNS) Inconel 625 alloy were investigated using SEM, TEM and ball-on-disc sliding wear tester. The results show that surface mechanical grinding treatment(SMGT) induced an approximately 800 μm-deep gradient microstructure, consisting of surface nano-grained,nano-laminated, nano-twined, and severely deformed layers, which resulted in a reduced gradient in micro-hardness from 6.95 GPa(topmost surface) to 2.77 GPa(coarse-grained matrix). The nano-grained layer resulted from the formation of high-density nano-twins and subsequent interaction between nano-twins and dislocations. The width and depth of the wear scar, wear loss volume, and wear rate of the SMGT-treated sample were smaller than those of untreated coarse-grained sample. Moreover, the wear mechanisms for both samples were mainly abrasive wear and adhesive wear, accompanied with mild oxidation wear. The notable wear resistance enhancement of the GNS Inconel 625 alloy was attributed to the high micro-hardness, high residual compressive stress, and high strain capacity of the GNS surface layer.

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.

Corrosion behavior of Mg−Li alloys:A review

It has been known that the lack of excellent corrosion resistance is the key problem restricting the wide application of Mg−Li alloys.Based on a quantity of literature about corrosion behavior of Mg−Li alloys,this review elaborates the factors affecting the corrosion behavior of Mg−Li alloys and the processing methods for improving corrosion resistance.The corrosion characteristics of Mg−Li alloys are described firstly.Then,it is explained that the grain size,orientation,second phase,and surface film strongly influence corrosion performance,which can be tailored by alloying,plastic deformation,and heat treatment.Further in-depth discussion about the corrosion mechanisms for Mg−Li alloys was also presented.Finally,important points of improving corrosion resistance are suggested.

关于延长导焦溜槽使用时间的探讨

对焦仓导焦溜槽入焦口频繁破损、更换困难这一生产难题进行研究,采用嵌入式铬钼合金表面焊接处理耐磨夹套对焦仓导焦溜槽进行改造,以解决因焦炭冲击、磨损导致导焦溜槽频繁更换的状况。

Preparation and bioactive surface modification of the microwave sintered porous Ti-15Mo alloys for biomedical application

Biomedical porous Ti-15 Mo alloys were prepared by microwave sintering using ammonium hydrogen carbonate（NH4HCO3） as the space holder agent to adjust the porosity and mechanical properties. The porous Ti-15 Mo alloys are dominated by β-Ti phase with a little α-Ti phase, and the proportion of α and β phase has no significant difference as the NH4HCO3 content increases. The porosities and the average pore sizes of the porous Ti-15 Mo alloys increase with increase of the contents of NH4HCO3, while all of the compressive strength, elastic modulus and bending strength decrease. However, the compressive strength, bending strength and the elastic modulus are higher or close to those of natural bone. The surface of the porous Ti-15 Mo alloy was further modified by hydrothermal treatment, after which Na2Ti6O13 layers with needle and flake-like clusters were formed on the outer and inner surface of the porous Ti-15 Mo alloy. The hydrothermally treated porous Ti-15 Mo alloy is completely covered by the Ca-deficient apatite layers after immersed in SBF solution for 14 d, indicating that it possesses high apatiteforming ability and bioactivity. These results demonstrate that the hydrothermally treated microwave sintered porous Ti-15 Mo alloys could be a promising candidate as the bone implant.

Effects of the laser surface treatment on the mechanical properties of CuZr-based bulk metallic glasses

Surfaces of three types of CuZr-based bulk metallic glasses （BMGs） were modified by laser surface treatment （LST）, and the influence of the treatment on structure and mechanical properties of these alloys was investigated. The phase structure of as-cast and laser-treated samples was characterized by XRD and the morphology of the alloys after fracture was examined by SEM. The compressive plasticity of treated Cu47.sZr47.sAI5 and Cu46.sZr47.sAlsCo~ BMGs can be improved from 0.5% to 2.0% and from 1.2% to 5.7% respectively compared with the as-cast ones, while （Cu0.55Zr0.40Ala05）99Er~ BMG shows insignificant change of plasticity. The improvement in plasticity is attributed to induced crystallization of B2 CuZr phase in the treated sur- face zone of selected metallic glasses.