材料期刊网

OXIDATION OF A TWO-PHASE Cu-75Cr ALLOY IN AIR AT 700-900℃

F. Gesmundo , Y Niu , F. Vianiand D.L. Douglass(Universita di Genova , Fiera del Mare , Pad. D , 16129 Genova , Italy)(State Key Lab. for Corrosion and Protection , Institute of Corrosion and Protection of Metals , theChinese Academy of Sciences , Shenyang 110015 , China)(University of Arizona , 4715 East Fort Lowell Road , TUcson , AZ 85712 , USA)

金属学报(英文版)

The cormsion in air of a two-phase Cu-75Cr alloy was studied at 700-900℃. Thealloy cormded nearly parabolically at 700-800℃, but at 900℃ its instantaneousparabolic mte constant decreased with time. The scales were complex and consistedof an outermost layer of copper oxide generally followed bg a layer of the double ox-ide Cu2 Cr2 O4 sometimes containing particles of unoxidized chromium surmunded bya chromia layer. An innermost layer of chromia was also observed in some cases.Finally metallic copper was al8o frequently mixed with chromia particles. No Cr de-pletion was observed in the alloy close to the inteffoce with the scale. In any case,this alloy was not able to form an exclusive continuous protective chromia layer. Thespecial cormsion behavior Of this alloy is typical of two-phase binary systems with alange solubility gaP in which the outwaof dthesion fiux of the most-reactive componentin the alloy is strongly reduced and may be inswncient to fOrm a protective externallayer of the cormsponding oxide. In paTticular, the presence of particles of Cr withina double oxide layer is very unusual and is allowed only for the kinetic reason.

关键词: copper-chromium , null , null , null

Hot Cracking in AZ31 and AZ61 Magnesium Alloy

C.J. Huang

材料科学技术（英文）

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS) was used for component analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid Mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone (PMZ). In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher (6 wt%) Al content and produced much liquefied Mg₁₇Al₁₂ at grain boundaries under multiple thermal cycles. The liquefied Mg17Al12 were pulled apart and hot cracks formed at weld metal HAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length (TCL) in one thermal cycle compared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. Consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.

关键词: Varestraint test

Hot Cracking in AZ31 and AZ61 Magnesium Alloy

C.J. Huang

材料科学技术（英文）

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS) was used for component analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid Mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone (PMZ). In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher (6 wt%) Al content and produced much liquefied Mg₁₇Al₁₂ at grain boundaries under multiple thermal cycles. The liquefied Mg17Al12 were pulled apart and hot cracks formed at weld metal HAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length (TCL) in one thermal cycle compared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. Consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.

关键词: Varestraint test

Corrosion behaviour of AZ21, AZ501 and AZ91 in sodium chloride

Corrosion Science

The corrosion behaviour of AZ21, AZ501 and AZ91 was studied in 1 N NaCl at pH 11 by measuring electrochemical polarization curves, electrochemical AC impedance spectroscopy (EIS) and simultaneously measuring the hydrogen evolution rate and the: magnesium dissolution rate. The corrosion rates increased in the following order: AZ501 < AZ21 < AZ91. The: corrosion behaviour was related to alloy microstructure as revealed by optical and electron microscopy. The beta phase was very stable in the test solution and was an effective cathode. The beta phase served two roles, as a barrier and as a galvanic cathode. If the beta phase is present in the alpha matrix as intergranular precipitates with a small volume fraction, then the beta phase mainly serves as a galvanic cathode, and accelerates the corrosion of the alpha matrix. If the beta Fraction is high, then the beta phase may mainly act as an anodic barrier to inhibit the overall corrosion of the alloy. The composition and compositional distribution in the alpha phase is also crucial to the overall corrosion performance of dual phase alloys. Increasing the aluminum concentration in the alpha phase increases the anodic dissolution rate and also increases the cathodic hydrogen evolution rate. Increasing the zinc concentration in the alpha phase may have the opposite effect. (C) 1998 Elsevier Science Ltd. All rights reserved.

关键词: magnesium alloys;corrosion;negative difference effect;microstructure;magnesium alloys;electrode

AZ31与AZ61异种镁合金的TIG焊研究

彭建 , 周绸 , 陶健全 , 潘复生

材料工程 doi:10.3969/j.issn.1001-4381.2011.02.010

采用TIG焊对AZ31与AZ61镁合金薄板进行连接,分别采用了AZ31和AZ61焊丝,比较焊接效果的影响.通过显微镜、扫描电镜、X-ray物相检测等实验方法,分析了两种焊丝焊接接头的外观形貌、显微组织、焊缝析出相及力学性能等差异.研究结果表明:采用AZ31和AZ61两种焊丝都能完成AZ31与AZ61镁合金薄板的对焊,获得无缺陷的焊接接头;焊缝区均存在α-Mg和β-Mg17Al12两种相,两侧母材存在热影响区,靠近焊缝处晶粒粗化,但AZ31侧晶粒粗化比AZ61侧明显.采用AZ31焊丝与采用AZ61焊丝相比,AZ31母材侧的粗晶区宽度更窄,断裂处更靠近中心线,强度为161MPa,达到AZ31挤压板母材的64%左右;AZ61焊丝的焊接接头平均强度为210MPa,可达到AZ31母材的84%.

关键词: AZ31镁合金 , AZ61镁合金 , TIG焊 , 微观组织 , 力学性能

AZ91系列镁合金防蚀技术简述

刘亚莉 , 刘超锋 , 王振保 , 刘建秀 , 纪莲清

材料保护

AZ91系列镁合金用途广泛,提高其耐腐蚀性能意义重大.对AZ91系列镁合金的多种防腐蚀技术进行了简述.

关键词: AZ91 , 镁合金 , 耐蚀性

AZ91D镁合金凝固过程分析

张丁非 , 张红菊 , 刘荣燊 , 段红玲 , 石国梁

材料导报

采用差热法以及冷却曲线测定AZ91D镁合金的相变温度,通过金相试验,研究了AZ91D镁合金凝固过程中显微组织的变化,为制定合理的AZ91D镁合金热处理工艺,提高合金力学性能提供了依据.

关键词: AZ91D镁合金 , 热分析 , 相变温度 , 显微组织

Effect of Cooling Conditions on Grain Size of AZ91 Alloy

Zhiliang NING , P.CAO , H.WANG , Jianfei SUN , Diankun LIU

材料科学技术（英文）

The grain size of AZ91 alloy was investigated in terms of the effects of cooling rate, superheat and steel gauze. It was found that rapid cooling rate and low superheat favoured the achievement of fine grain structures. The gauze had a less profound effect on the grain size in AZ91 magnesium alloy than that in A356 aluminum alloy. The mechanisms by which these factors affect grain refinement of AZ91 have also been discussed.

关键词: Superheat , null , null , null

AZ镁合金在高氯酸镁溶液中的电化学行为

陈昌国 , 张佩红 , 尧玉芬 , 刘渝萍 , 陈浩 , 余丹梅

稀有金属材料与工程

用失重、线性电位扫描、交流阻抗、恒流放电等多种方法研究了AZ镁合金在1.0mol/LMg(ClO4)2溶液中的电化学行为,考察了它们作为镁电池负极材料的性能.浸泡与伏安实验结果表明,AZ21的自腐蚀比AZ31和AZ61严重;AZ21和AZ31的电化学活性优于AZ61,表现为阳极极化小,开路电位负.交流阻抗结果表明AZ21、AZ31、AZ61的Rct值逐渐增加.恒电流放电发现,AZ31的放电电何负且稳定;电流效率为82%,高于AZ21和AZ61;滞后时间2 s,小于AZ21和AZ61.可望用于Mg电池.

关键词: AZ镁合金 , 高氯酸镁 , 电化学行为 , 镁电池

Effect of the width on AZ31 sheet rolling

Qingwei DAI

金属学报(英文版)

A pyramid sheet has been used in experiments and three-dimensional finite element simulation to study the edge cracks and effects of width on AZ31 sheet under rolling. Results show that the edge cracks of Mg sheet comply with the Normalized Crockroft & Latham theory. It can be predicted by D=-0.124+0.09X-0.008X², if D≥0, the edge cracks occur. The sheet shearing deformation at the edge brings about cracks. The strain rate changes periodically with different X. With initial width increases, the recrystallized grain size decreases. The finite element model has been validated by the experiment results.

关键词: Finite elements method , 镁合金 , 轧制 , 边裂