AZ镁合金在高氯酸镁溶液中的电化学行为

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1.0 mol/L Mg(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的放电电位负且稳定;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。     

Effect of yttrium and calcium additions on electrochemical behaviors and discharge performance of AZ80 anodes for Mg−air battery

The effects of yttrium (Y) and yttrium + calcium (Y+Ca) additions on the electrochemical properties and discharge performance of the as-extruded Mg?8Al?0.5Zn?0.2Mn (AZ80) anodes for Mg?air batteries were investigated. The results show that the addition of 0.2 wt.% Y increased the corrosion resistance and discharge activity of AZ80 anode. This was attributed to the fine and spherical β-Mg₁₇Al₁₂ phases dispersing evenly in AZ80+0.2Y alloy, which suppressed the localized corrosion and severe “chunk effect”, and facilitated the rapid activation of α-Mg. Combinative addition of 0.2 wt.% Y and 0.15 wt.% Ca generated grain refinement and a reduction of the β-Mg₁₇Al₁₂ phase, resulting in a further enhancement in discharge voltage. However, the incorporation of Ca in Mg₁₇Al₁₂ and Al₂Y compounds compromised the corrosion resistance and anodic efficiency of AZ80+0.2Y+0.15Ca anode. Consequently, AZ80+0.2Y anode exhibited excellent overall discharge performance, with the peak discharge capacity and anodic efficiency of 1525 mA·h·g^?1 and 67% at 80 mA/cm², 13% and 14% higher than those of AZ80 anode, respectively.     

Effects of Er on the microstructure and properties of AZ31 magnesium alloy prepared via the EMS process

The effects of small amounts of the rare-earth element erbium on the microstructure and the mechanical properties of AZ31 magnesium alloy via the electromagnetic stirring(EMS) process have been studied.It has been shown that AZ31-Er alloys are mainly composed of α-Mg solid solution and β-Mg17Al12 phases.When the Er content reaches 0.12 wt.%,the characteristic peaks of Al2Er can be observed.The micro-structure is obviously refined and the tensile strength of the AZ31-based alloy at ambient temperature is significantly improved by contents of 0.03 wt.% Er,especially the elongation(δ=19%).More addition of Er obviously decreases the tensile strength and elongation of the AZ31-based alloy because of the grain coarsening and the reduction of β-Mg17Al12 phases.     

Electrochemical Performance of AZ31 Magnesium Alloy under Different Processing Conditions

为选择一种高性价比的镁电池阳极材料,借助电化学工作站、光学显微镜(OM)、扫描电子显微镜(SEM)和X射线能谱分析(EDS)对不同加工状态的AZ31B镁合金电化学性能进行研究。分别将挤压、轧制、铸轧和铸态AZ31B镁合金作为阳极材料,测试其电化学性能。结果表明,在4种加工状态下,挤压态镁合金是性价比最高的一种阳极材料;其组织由均匀细小的晶粒和第二相组成,拥有最负的平衡电位,最低腐蚀电流密度和最小自腐蚀速率;挤压态样品腐蚀后,表面产生疏松细小,且均匀分布的腐蚀产物,降低了阳极极化,增加了阳极利用率。轧制和铸轧态的AZ31B镁合金的电化学活性和耐蚀性能相对挤压态的较低。铸态AZ31B镁合金由于较粗大的晶粒、第二相和铸造缺陷,表现出不稳定的放电曲线和较正的放电电位。不同状态AZ31镁合金的腐蚀均以点蚀为主。     

镁合金阳极材料在海水中放电的电化学性能(英文)

镁合金可以作为海水激活电池阳极材料来使用。研究了AZ31、AP65和Mg-3%Ga-2%Hg 3种镁合金在海水中放电的电化学性能。Mg-3%Ga-2%Hg合金的阳极极化曲线表明,该合金具有比AZ31和AP65合金更负的腐蚀电位。恒电流放电实验结果表明,Mg-3%Ga-2%Hg合金在海水中表现出更好的阳极放电性能。交流阻抗测试表明,镁合金阳极和海水接触表面的电化学反应决定反应的活性,Mg-3%Ga-2%Hg 合金中的Mg3Hg和Mg21Ga5Hg3化合物比AZ31合金中的Mg17(Al,Zn)12相以及AP65合金中的铅在镁中形成的固溶体具有更好的电化学活性。     

Effect of Ca addition on microstructure of twin-roll cast AZ31 Mg alloy

A twin-roll cast (TRC) AZ31-0.7Ca alloy sheet has been subjected to thermo-mechanical treatment (TMT) followed by annealing and its microstructure was evaluated. The as-cast microstructure of TRC AZ31-0.7Ca alloy is essentially similar to that of TRC AZ31 alloy, except for the presence of Al₂Ca dispersoid particles. The presence of Al₂Ca particles imparts significant changes to the microstructure of TMT-ed TRC alloy such as the refinement of grain size and evolution of textures different from those of ingot cast and TRC AZ31 alloys.     

Discharge performance of Mg-Al-Pb-La anode for Mg-air battery

The discharge performance of Mg-Al-Pb-La anode was investigated by electrochemical techniques and compared with that of Mg-Al-Pb alloy. The results indicate that the Mg-Al-Pb-La anode provides enhanced corrosion resistance at open circle potential, and exhibits better discharge activity than the Mg-Al-Pb alloy. The utilization efficiency of Mg-Al-Pb-La anode is higher than that of commercial Mg-Al-Zn (AZ) and Mg-Al-Mn (AM) alloys. A single Mg-air battery with Mg-Al-Pb-La alloy as the anode and air as the cathode has an average discharge potential of 1.295 V and a discharge capacity of 1370 mA·h/g during discharge at 10 mA/cm², which is higher than that of batteries using Mg-Li anodes. The enhancement in discharge performance of the Mg-Al-Pb-La anode is caused by its modified microstructure, which reduces the self-corrosion and accelerates the spalling of oxidation products during battery discharge. Furthermore, the dissolution mechanism of Mg-Al-Pb-La anode during the discharge process was analyzed.     

Microstructural evolution and mechanical properties of Mg95.5Y3Zn1.5 alloy processed by extrusion and ECAP

A Mg_95.5Y₃Zn_1.5 alloy processed via a two-step processing route of extrusion plus ECAP has been investigated. It was found that the ECAP processed Mg_95.5Y₃Zn_1.5 alloy contained ultrafine grains and exhibited excellent mechanical properties. After ECAP, the average grain size of Mg_95.5Y₃Zn_1.5 alloy was refined to about 300 nm. The highest strengths, with yield strength of 444.6 MPa and ultimate tensile strength of 472.7 MPa, were obtained after 1 pass at 623 K. The SAED patterns indicated that the microstructure after ECAP consisted of both high angle and low angle grain boundaries. The fraction of high-angle boundaries increased with increasing numbers of ECAP passes. The Mg_95.5Y₃Zn_1.5 alloy contained a high volume fraction of X-Mg₁₂ZnY phase due to high yttrium and zinc addition. And, it accelerated the growth and coalescence of cracks during tensile testing, resulting in premature fracture and lower elongation of alloy.     

Microstructure evolution and mechanical behavior of AZ31 Mg alloy processed by equal-channel angular pressing

AZ31 Mg alloy bar was subjected to 8-pass equal-channel angular pressing(ECAP) at 623 K. Microstructure evolution was observed by optical microscopy(OM) on cross section and X-ray diffraction analysis. The room temperature mechanical properties of the ECAP processed specimens were also investigated. A fine-grained structure with an average sub-grain size of 9 μm is obtained after 7 ECAP passes. XRD analysis indicates that after ECAP, in placing of planes and become the dominant directions that are favourable for grain refinement. ECAP processed AZ31 Mg alloy exhibits significant improvement in elongation but decrease in strength. The elongation of the specimen increases continuously up to 2 passes and then remains stable at further passes. This improvement can be related to the evolution of crystallographic texture and the scattered orientation of the basal plane (0001).     

Influence of multipass high rotating speed friction stir processing on microstructure evolution,corrosion behavior and mechanical properties of stirred zone on AZ31 alloy

The influence of multipass high rotating speed friction stir processing (FSP) on the microstructure evolution, corrosion behavior, and tensile properties of the stirred zone (SZ) was investigated by EBSD, TEM, SEM, electrochemical workstation and electronic universal testing machine. The mean grain size of the SZ is significantly refined, and it increases with the increase of the processing pass. In addition to an obvious increase in the number, the distribution of β-Al₁₂Mg₁₇ precipitates also becomes more uniform and dispersed with increasing the processing pass. Compared with the as-received AZ31 alloy, the tensile properties of the SZ are hardly improved, but the corrosion resistances are significantly enhanced. The corrosion potential of the SZ prepared by 4-pass FSP is increased from −1.56 V for the unprocessed AZ31 alloy to −1.19 V, while the corrosion current is decreased from 1.55×10⁻⁴ to 5.47×10⁻⁵ A.     

Microstructure refinement of AZ31 alloy solidified with pulsed magnetic field

The effects of a pulsed magnetic field on the solidified microstructure of an AZ31 magnesium alloy were investigated. The experimental results show that the remarkable microstructural refinement is achieved when the pulsed magnetic field is applied to the solidification of the AZ31 alloy. The average grain size of the as-cast microstructure of the AZ31 alloy is refined to 107 μm. By quenching the AZ31 alloy, the different primary α-Mg microstructures are preserved during the course of solidification. The microstructure evolution reveals that the primary α-Mg generates and grows in globular shape with pulsed magnetic field, contrast with the dendritic shape without pulsed magnetic field. The pulsed magnetic field causes melt convection during solidification, which makes the temperature of the whole melt homogenized, and produces an undercooling zone in front of the liquid/solid interface, which makes the nucleation rate increased and big dendrites prohibited. In addition, the Joule heat effect induced in the melt also strengthens the grain refinement effect and spheroidization of dendrite arms.     

ECAP变形对MWCNTs/AZ31复合材料抗腐蚀性能的影响

采用碳纳米管孕育块铸造法制备多壁碳纳米管/AZ31镁基复合材料,经等径角挤压(ECAP)变形后对复合材料在3.5%NaCl(质量分数)的腐蚀介质中进行静态浸渍试验和电化学极化曲线测定,研究等径角挤压变形工艺对复合材料抗腐蚀性能的影响;利用数码相机、扫描电子显微镜对复合材料腐蚀前后的表面形貌进行观察和分析;并对复合材料的抗腐蚀机理进行分析。结果表明:等径角挤压变形工艺能有效的提高多壁碳纳米管(CNTs)/AZ31复合材料的抗腐蚀性能,经等径角挤压变形4道次后,复合材料的平均腐蚀速率由挤压态的0.6035mg/(m2·s)降为0.2963mg/(m2·s)。腐蚀电流密度Icorr由ECAP变形前的3.363μA/cm2减小到2.269μA/cm2。     

转模等通道转角挤压路径对AZ31镁合金组织和力学性能的影响

利用3D转模等通道转角挤压(3D-RD ECAP)设备, 对AZ31镁合金进行了A', B_A', B_C'与C' 4种路径的ECAP实验. 对试样的显微组织观察显示, 经4种路径挤压后合金显微组织都明显细化, 但不同路径对微观组织和力学性能的影响不同. 经A' 和B_A'路径挤压的试样组织中晶粒尺寸和硬度分布比其它两种路径挤压的试样更均匀, 且显示出更高的塑性. 通过对各种路径挤压过程中试样内部立方单元的变形分析, 揭示了传统的剪切模型理论的不足. 利用有限元方法模拟了试样ECAP的形变过程, 证实材料在变形过程中各部位受力差异很大. ECAP对试样变形的均匀性主要取决于拉/压应力交替作用于试样各个部位的顺序, 而与传统剪切模型中的立方单元变形规律没有直接关系.     

AZ91镁合金的挤压和析出硬化行为(英文)

挤压比为4:1,将铸态AZ91镁合金分别在250,300和350℃下进行挤压,随后进行析出硬化处理(T6)。经过热挤压和析出硬化处理后,铸态AZ91镁合金中粗大的和偏析Mg17Al12析出相被细化并均匀分布在α-镁基体中。在不同的挤压温度下合金中发生了部分或全部动态再结晶。经挤压后,该合金的极限抗拉强度从铸态的190MPa增加到570MPa。AZ91镁合金的时效硬化特征与晶粒尺寸有关。在250、300和350℃下以4:1的挤压比挤压该合金后,获得峰值硬度的时效时间分别为35、30和20h。SEM观察到在AZ91基体中存在均匀细小的Mg17Al12析出相。     

Microstructure evolution of TA15 titanium alloy subjected to equal channel angular pressing and subsequent annealing at various temperatures

TA15 titanium alloy was successfully processed for the first time by equal channel angular pressing (ECAP) in the temperature range of 900-1000 °C and annealed in a wide temperature interval from 650 to 800 °C. The investigation was achieved by light microscope (LM), scanning electron microscope (SEM) and transmission electron microscope (TEM) on the microstructure evolution of TA15 alloy subjected to ECAP and subsequent annealing after ECAP. In the present work, equal channel angular pressing (ECAP) was taken as the effective method to acquire severe plastic deformation (SPD). The studies we have performed show that grains have been obviously refined and well globularized after ECAP. When TA15 alloy was pressed at the temperatures of α + β phase region equiaxed microstructure was created. There was an increase in the equilibrium grain size with increasing pressing temperature, while a decrease in the volume fraction of equiaxed α phase. TEM microstructural images illustrate that an amount of deformation twins emerged while pressing TA15 below α-β transformation temperature (T_β), which led to the continued plastic deformation through the restarting of many slip bands. Severe coarsening took place in β grains during ECAP at the temperature above T_β. A larger number of well globularized and more homogeneous equiaxed α phase of TA15 alloy annealed after ECAP has been attained. Furthermore, with annealing at the optimum temperature, grains have not grown significantly.     

Effect of tin addition on microstructure and electrochemical properties of rolled AZ61-Sn magnesium anodic materials

Microstructure characterization,corrosion behavior,and electrochemical properties of magnesium anode materials containing 1-3 wt.% Sn in AZ61 alloy were studied by optical microscopy,X-ray diffraction(XRD) ,scanning electron microscopy(SEM) ,and energy-dispersive spectroscopy(EDS) ,constant current method,potential polarization,and drainage.The results showed that amount of Mg2Sn phase increased,and recrystallization ratio of Sn-contained Mg alloys during rolling process was improved with increasing of Sn content.This resulted in uniform and refined grains.The results also demonstrated that discharge potential was improved and hydrogen release rate was reduced with the addition of Sn.As the current density increased,the release hydrogen rate was rising,owing to negative variance effect of magnesium alloys.The current efficiency gets to 87% at 20 mA/cm2.The main components of the corrosion products are easy-to-peel-off MgO and Al2O3 that can lead to more negative and stable work potential and accelerate battery reaction continuously.     

Preparation of submicrocrystal Al-Ti-B master alloy and its influence on microstructure and properties of AZ91D

To improve the mechanical properties of AZ91D magnesium alloy,the submicrocrystal Al-Ti-B master alloy was prepared with copper mold inject casting method,and the influence of submicrocrystal Al-Ti-B master alloy on the microstructure and mechanical properties of AZ91D was investigated.Results show that,the distribution of Ti B_2 phase in submicrocrystal Al-Ti-B alloy is even and disperse,and the average size of Ti Al_3 phase is reduced from 10-30μm to～1μm.The properties of AZ91D refined with submicrocrystal Al-Ti-B master alloy are better than that with coarse-grained Al-Ti-B master alloy without copper mold inject casting.The tensile strength,elongation and Brinell hardness of AZ91D are increased by 10.6%,25%and 18.1%,respectively.Therefore,refinement of AZ91D with submicrocrystal Al-Ti-B that is obtained by copper mold inject casting is an effective method to improve its mechanical properties.     

高精度AZ31镁合金薄壁管件等温挤压后的组织与性能

研究了不同条件下AZ3l镁合金管材的等温挤压情况,并对挤压前后材料组织与力学性能的变化进行了分析.研究结果表明,AZ31镁合金热挤压时发生了动态再结晶,材料组织比铸态时细化,力学性能大幅度提高;在(653±10)K挤压温度范围内金属流动均匀,挤出管材尺寸精度较高,力学性能良好;从综合性能看,AZ31镁合金挤压产品的合适退火工艺为573 K × 2 h;此时管材的机械拉伸强度为260 MPa,伸长率为23%.     

热挤压工艺对AZ31镁合金组织与力学性能的影响

在不同挤压条件下对AZ31镁合金进行了热挤压试验,并对挤压前后材料组织与力学性能的变化进行了分析.研究结果表明,AZ31镁合金热挤压时发生了动态再结晶,材料组织比铸态时细化,力学性能大幅度提高;AZ31镁合金挤压后的组织及力学性能受挤压温度及冷却方式影响,在本试验范围内,AZ31镁合金在623 K挤压后空冷得到的组织均匀细小,力学性能良好.     

Using X-ray microtomography to evaluate cavity formation in a superplastic magnesium alloy processed by equal-channel angular pressing

The magnesium AZ31 alloy exhibits excellent superplastic properties after processing by equal-channel angular pressing (ECAP) and testing in tension at a temperature of 623 K. Experiments show that there is an increase in the elongations to failure with increasing numbers of passes in ECAP. X-ray microtomography was used to obtain detailed information on the morphologies of cavities developed during superplastic flow and the results were analyzed in terms of the different possible cavity growth mechanisms. The results show that superplastic elongations are attained in this alloy because the finer grain structure introduced by ECAP is associated with lower flow stresses in tensile testing at elevated temperatures and this leads to a reduction in the rate of growth of internal cavities.