Stirring brazing of dissimilar Al/Mg alloy without flux in air

AZ31B magnesium alloy and 2024 aluminum alloy were successfully jointed at aid of mechanical stirring with Sn-Zn-Al filler metal. The microstructure, fracture morphologies, and mechanical properties of joint were investigated. The results show that Mg-Al intermetallic compounds can be avoided by the process. But, a small quantity of porosity is found in the joint. The sheafing strength of joint interface adjacent to magnesium alloy is 35.4 MPa for formation of Mg-Sn intermetallic compounds, which is about 46 % of that of filler metal. While, the shearing strength of joint interfaces adjacent to aluminum alloy is 70.4 MPa for formation of Zn-Sn-Al solid solution, which is about 92 % of that of filler metal.     

GWN751K镁合金均匀化热处理

通过OM、SEM及布氏硬度分析,研究GWN751K镁合金在不同状态下的显微组织与性能,确定该合金的双级均匀化工艺参数。结果表明:合金经过440℃、6h初级均匀化后,共晶组织开始发生分解,晶粒开始长大;经过535℃、16h热处理后,合金晶粒明显长大,但元素分布较为均匀,晶界处仅明显残留含Y化合物;均匀化处理使合金的力学性能得到改善,合金断裂强度为245MPa,屈服强度为192MPa,伸长率为12%,较铸态合金的力学性能均有所提高;合金变形抗力较铸态合金的有所增加,这种特性在450℃仍保留下来,但差别减小。     

A Master Alloy for the Spheroidisation of Needle-form Iron Compounds in Aluminium Alloys

Abstract

By use of a master alloy, Al-10% Mn-2% Ti, the long needle-form iron compounds in Al-Si, Al-Mg and Al-Zn alloys can be transformed into a spheroidal shape under normal casting conditions. After addition of the master alloy, the elongation of an Al-Si alloy containing 1.4% Fe is increased by over 80%, as compared with an alloy where the iron compounds remain in the needle-like form. The spheroidisation mechanism of the needle-form iron compounds is also considered in this paper.     

稀土银合金显微组织观察与分析

对稀土银合金材料进行了金相观察和电子探针扫描分析以及显微硬度测定。实验结果表明,添加两种性质差交大的稀土元素可以充分发挥互补作用,改善银合金的组织与性能。含有稀土钇的银合金有较强的加工硬化效果和较好的抗高温氧化作用。稀土钇与轻稀土元素组合添加将有助于改善银合金的综合性能。     

表面扩渗Al,Zn处理对ZM5镁合金性能的影响

通过铝锌(Al,Zn)混合粉对ZM5镁合金进行了表面固态扩渗铝锌(Al,Zn)处理,在衬底形成了Mg-Al-Zn合金层.研究结果表明:Mg-Al-Zn合金层主要由Mg-Al-Zn固溶体和Mg-Al-Zn金属间化合物(Al6Mg10Zn,Al5MgllZn4)组成,该合金层不仅使ZM5镁合金表面合金层显微硬度显著提高,而且在盐水浸泡腐蚀过程中,在衬底与腐蚀介质之间起到了良好的屏障作用,从而赋予试样良好的腐蚀性能.     

Fe-Y合金在800℃空气中的氧化行为

研究了Fe-5Y和Fe-10Y合金在800℃空气中的氧化行为。结果表明：二元Fe-Y合金氧化动力学曲线不规则,此温度下Fe-10Y合金的氧化速率高于Fe-5Y合金的氧化速率。Fe-5Y合金及Fe-10Y合金形成了相似的氧化膜结构,且它们都发生了内氧化现象。同时合金未形成单一的Y₂O₃层,这归结于Y在Fe中非常低的溶解度及合金中两相共存而阻碍了Y通过合金向外扩散。     

Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl₃ and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m² in a solution containing 1.53 mol/L H₂SO₄ and 0.018 5 mol/L Al₂(SO₄)₃·16H₂O at 20 °C. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.     

铬酸钠对铀钛合金在氯化钠溶液中的缓蚀作用

采用失重法和电化学方法研究了铬酸钠对铀钛合金在200 mg/L氯化钠溶液中的缓蚀作用,并用X射线光电子能谱(XPS)和激光共聚焦显微镜分析铀钛合金表面氧化物成分和形貌。结果表明,铬酸钠属于阳极型钝化剂,缓蚀效率随浓度的增加而增大。但溶液温度对铬酸钠的缓蚀效率影响较大,溶液温度高于45℃时,加入100 mg/L的铬酸钠对铀钛合金具有加速腐蚀作用。XPS分析表明,铀钛合金表面形成的钝化膜中铀的氧化物存在两种形式,最外层为UO2+x,内层为UO2;加入铬酸钠后,钝化膜最外层含有UO2+x和多种铬化合物,厚度小于3 nm。     

Al-5C中间合金对AZ31镁合金的细化机理

采用粉末原位合成工艺制备Al-5C中间合金,研究Al-5C中间合金对AZ31镁合金晶粒细化的影响及细化机理。结果表明：Al-5C中间合金由α（Al）和 Al 4 C 3两相组成,Al 4 C 3颗粒的尺寸分布由烧结时间控制。Al-5C中间合金能显著地细化AZ31镁合金晶粒尺寸,当Al-5C中间合金添加量低于2%时,随着Al-5C中间合金添加量的增加,AZ31镁合金晶粒尺寸减小。晶粒细化机理是由于 Al4C3与 Mn 反应生成的Al-C-Mn 颗粒能作为初生α-Mg晶粒的异质形核基底,从而细化晶粒。     

Ag-Cu-Ti活性钎料热力学分析

在陶瓷与金属的活性钎焊连接技术中，Ag—Cu—Ti合金是研究和应用最多的钎料之一。合金组元Ti的活度是影响钎料／陶瓷界面反应的关键因素，对钎料与陶瓷的润湿性和连接能力起着重要的作用。作者借助热力学对Ag—Cu—Ti活性钎料进行了热力学分析，重点分析了Ti的热力学活度及其与组分浓度之间的关系，计算了各组分之间的相互作用参数。分析和计算结果表明，Ti的活度随着Cu含量的增加而减小，随着Ag含量的增加而增大；Ag与Ti之间存在较大的排斥作用，两者的相互作用参数为32．83kJ／mol；而Cu与Ti之间存在强烈的吸引作用，其相互作用参数为-16．14kJ／mol；Ag—Cu—Ti合金中添加某些与Cu的结合力大、与Ti的结合力小、且与合金组元不形成高熔点化合物或脆性相的合金元素，有利于提高合金中的Ti活度。     

The effect of solid diffusion surface alloying on properties of ZM5 magnesium alloy

In this research, solid diffusion process was used to form a diffusion alloying layer on the surface of ZM5 magnesium alloy to improve corrosion and wear resistance. It is shown that the solid diffusion layer was mainly composed of Mg–Al–Zn intermetallic compounds and Mg–Al–Zn solid solution transition zone that had more Zn and Al elements than untreated ZM5 magnesium substrate. The continued immersion test in 3% NaCl solution displayed that the diffusion-treated specimen had better corrosion resistance compared to the untreated ZM5 specimen. The polarization test indicated that the Mg–Al–Zn intermetallic compounds of the diffusion alloying layer were an effective corrosion barrier to decrease the corrosion rate for ZM5 magnesium alloy when exposed to 3% NaCl solutions. In addition, the microhardness values of the Mg–Al–Zn intermetallic compounds were much higher than those of the substrate and this would greatly contribute to the enhancement of wear resistance.     

Corrosion of Fe-15Ce alloy in three mixed-gas atmospheres

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Thermodynamic calculation of intermetallic compounds in AZ91 alloy containing calcium

1 Introduction Magnesium alloy is regarded as a promising structural material in the 21 century because of its excellent properties such as low density, high specific strength, good castability and machinability[1?5]. The common magnesium alloy AZ91 is, however, unsuitable for using at the temperatures above 120 ℃ because of its poor creep resistance and strength at elevated temperatures[2]. Adding other elements, like calcium, is an important method to improve the mechanical properties of A…     

Sliding wear and friction behavior of ZA-27 alloy reinforced by Mn-containing intermetallic compounds

A ZA-27 alloy reinforced with M n-containing intermeta llic compounds was prepared and its tribological behaviors were investigated. By adding Mn, RE, Ti and B into ZA-27 alloy, the test alloy (ZMJ) was fabricated by sand casting. Microstructural analysis shows that considerable amount of Mn-containing intermetallic compounds such as Al5MnZn, Al9(MnZn)2 and Al65 Mn(RE)6Ti4Zn36 are formed. Compared to ZA-27, ZMJ shows better wear resistance, lower friction coefficient and lower temperature rise of worn surface under lubricated sliding condition. ZMJ also shows the lowest steady friction coefficient under dry friction condition. The wear resistance improvement of ZMJ is mainly attributed to the high hardness and good dispersion of these Mn-containing intermetallic compounds. It is indicated that the intermetallic compounds play a dominant role in reducing the sever adhesive and abrasive wear of the ZA-27 alloy.     

铝合金表面电火花沉积层组织与性能

采用电火花沉积技术,以硅青铜作为电极,在空气中对2A12铝合金表面进行了强化.采用扫描电镜、电子能谱分析仪与X射线衍射仪等仪器对沉积层的形貌、组织、元素分布和结构进行了分析与研究;利用显微硬度计和磨损试验机对沉积层的显微硬度与耐磨性进行了测试.结果表明,沉积层连续、致密,与基体呈冶金结合,无明显界面;主要由铜铝金属间化合物组成,显微硬度可达578 HV;沉积层耐磨性较基体显著提高,表面强化效果明显.     

表面渗硅处理提高钛铝基合金高温抗氧化性

使用Al-Si合金熔体对钛铝基合金进行表面渗硅处理，在表层发生了不同程度的界面反应，生成成分比较不同的以Si,Ti,Al三元互为主的物相，表面渗硅处理可明显增强钛铝基合金的高温抗氧化性，使1173K，100h的恒温氧化后，表面涂层氧化生成致密的Si-Ti-Al-O复杂氧化物，而且表面涂层与TiAl基体之间还发生了一定程度的界面反应，生成Ti-Si及TiAl2化合物。对于1053K渗硅处理的试样，在恒温氧化过程中，表面Si-Ti-Al化合物的局部区域已经转化成为更加稳定的Ti-Si化合物。     

30CrMnSi/Cu/V/TC4电子束焊接试验研究

使用Cu/V中间层实现了30CrMnSi合金钢与TC4钛合金的电子束焊接,探究了接头组织和性能特征.结果表明,通过添加Cu/V过渡层金属可以避免Ti-Fe元素的直接混合反应生成脆硬的金属间化合物.焊缝不同区域分布着不同组分及性能的特征相,靠近钢侧焊缝为偏聚形成的富Fe相与富Cu相,靠近钛侧焊缝在形成Ti-V固溶体的同时...     

Effect of mischmetal and yttrium on microstructures and mechanical properties of Mg-Al alloy

The effect of yttrium and mischmetal(MMs)on the as-cast and solid solution treated structures of Mg-Al alloys with different Al-contents was investigated.The results show that the MMs in Mg-Al alloy existed in rod Al4(Ce,La)compound while Y in Mg-Al alloy in polygonal Al2Y compound.The amount of Mg17Al12 in Mg-Al alloy is decreased with increasing Y or MMs addition,and Mg17 Al12 intermetallic compound is changed from continuous network to discontinuous one.The Al4(Ce,La)and Al2Y compounds are not dissolved into Mg-Al alloy matrix during solid solution treatment so that their high heat stability can be exhibited.The experiment of mechanical properties indicate that elongation and impact toughness of the Mg-Al-Y alloy with polygonal Al2Y compound are higher than those of Mg-Al-MMs alloy with rod A4(Ce,La) compound.     

Microstructure Control and High Temperature Properties of Al-Mn-Based AlloysEI北大核心CSCD

The process of production and working environment of heat exchangers call for materials with good elevated temperature properties. However, the previous investigations were mainly focused on their room temperature properties. The relationship between microalloying and high temperature properties, especially creep properties of Al-Mn-based alloys are barely discussed. In order to improve the industrial applications of Al-Mn-based alloys, the effect of Mg, Ni and Zr additions and annealing process on the microstructure and high temperature properties of Al-Mn-based alloys were studied in this work. The investigated alloys were treated in two ways, first one is cold-rolling and heat treatment at 873 K for 10 min, and the second one is cold-rolling, heat treatment at 623 K for 1 h and 873 K for 10 min. The results indicate that annealing process has remarkable effect on the grain shape, fine equiaxed crystal grains are obtained in the former, while stable elongated grains are obtained for precipitation precedes recrystallization at 623 K in the latter. With Mg addition, more AlMnSi phase precipitated during annealing. The addition of Zr and Ni increases the type and amount of heat resistant compounds, precipitate Al3Zr and AlMnSiNi, which are beneficial to improving high temperature properties of Al-Mn alloy. Al-Mn-0.3Mg-0.2Ni alloy has the best elevated temperature properties, and the tensile strength of it is 102 MPa (50 MPa higher than Al-Mn alloy) at 523 K. And the steady-creep rate is strongly decreased to 3.93x10(-8) s(-1), two orders of magnitude smaller than Al-Mn alloy at the temperature of 523 K under the stress of 40 MPa. With dispersoids complicated or increased, the movement of dislocations are pinned strongly, which are contribute to improving the creep properties of Al-Mn alloy for the creep is mainly controlled by dislocation climb.     

束流偏移对钒合金与不锈钢电子束阻隔熔化焊接头性能的影响

以金作为中间层采用电子束阻隔熔化焊方法来实现V-5Cr-5Ti钒合金与HR-2不锈钢之间的连接,研究电子束流的偏移对接头性能的影响.结果表明,不偏移电子束流(偏移距离d=0)焊接得到的钒合金与不锈钢接头界面将产生贯穿性裂纹,直接导致焊接失败.通过电子束流的偏移(偏移距离d等于束斑半径)一定程度降低了结合界面金属间化合物的产生,实现了钒合金与不锈钢的冶金结合.金作为中间层添加元素,很好地抑制了V/Fe界面的金属间化合物的产生,显著提高了接头性能,接头抗拉强度超过380 MPa.钒合金/不锈钢异种金属焊接接头焊缝正反面成形良好,X射线探伤未发现裂纹和气孔缺陷.