Formation of intermetallic compounds during reaction between Ti and Al-Mg alloys with various Mg contents

The reactions between Ti and Al-Mg alloys were systematically investigated by heating the Ti/Al-Mg al-loy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.%at 660°C.Mg element in the Al-Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al-Mg alloy powders,thus,promoting the reactions.In the samples with Mg contents varying from 5.09 wt.%to 25.93 wt.%,the first-formed intermetallic compound was Al_(18)Ti_(2)Mg_(3),and then Al_(3)Ti generated at the Al_(18)Ti_(2)Mg_(3)/Ti interface.Since the Mg content in the Al-Mg melts decreased during the subsequent heat-ing process,the previously formed Al_(18)Ti_(2)Mg_(3)in the Ti/Al-5.09Mg sample transformed into Al_(3)Ti accom-panied by the reaction of Al with Ti to newly form Al_(3)Ti,generating a single Al_(3)Ti phase.In contrast,the new formation of Al_(3)Ti and its transformation to Al_(18)Ti_(2)Mg_(3)proceeded continuously in the Ti/Al-13.54Mg and Ti/Al-25.94Mg samples,resulting in a mixture of Al_(18)Ti_(2)Mg_(3)and a little Al_(3)Ti residue.In the Ti/Al-40.54Mg sample,Al_(3)Ti was the unique reaction product throughout the heating process.The final Al_(3)Ti particles in the Ti/Al-5.09Mg sample were in a blocky shape,while they were in a plate-like form in the Ti/Al-40.54Mg sample,which was caused by the enhanced growth anisotropy due to the de-creased interfacial energy between Al_(3)Ti particles and Al-Mg melts with the increase of Mg content.A twin plane re-entrant mechanism was suggested for the growth of Al_(18)Ti_(2)Mg_(3)particles,weakening the anisotropic growth caused by the directional supply of Ti atoms,and contributing to the blocky mor-phology of Al_(18)Ti_(2)Mg_(3)particles.In addition,the volume difference between the formed Al_(18)Ti_(2)Mg_(3)and consumed Ti was greater than that between the Al_(3)Ti and Ti,and the Al_(18)Ti_(2)Mg_(3)has worse plasticity than the Al_(3)Ti,resulting in the Al_(18)Ti_(2)Mg_(3)reaction product fracturing more easily during thickening,thus forming a petal-like structure,but the Al_(3)Ti product being in an almost continuous layer.

Cu含量以及Cu/Mg比对Al-Si-Cu-Mg合金组织和力学性能的影响

研究了Cu含量和Cu/Mg比对Al-Si-Cu-Mg合金组织和力学性能的影响。结果表明Al-Si-Cu-Mg合金凝固组织是否形成Mg_(2)Si、Q-Al_(5)Cu_(2)Mg_(8)Si_(6)以及θ-Al_(2)Cu取决于Cu含量以及Cu/Mg比。当Cu/Mg比相对低时形成Mg_(2)Si中间相,而Cu/Mg比高时则倾向于生成Q-Al_(5)Cu_(2)Mg_(8)Si_(6)和θ-Al_(2)Cu相。当Cu/Mg比相同时,高Cu含量和高Mg含量都会促进Q相θ相的形成。通过观察T6热处理后的组织发现Cu含量以及Cu/Mg比控制了初生相的溶解以及析出相的形成,从而影响合金的强度与韧性。通过控制Cu含量及Cu/Mg比使Al-9Si-2Cu-0.5Mg合金中析出较少数量的初生相,再通过热处理析出大量的Q′强化相,使合金具有较高的强度和相对适中的伸长率。

Mg含量对ER5356铝合金焊丝熔敷金属组织和性能的影响

针对国产ER5356铝合金焊丝,用熔化极惰性气体保护焊(MIG)制备ER5356铝合金焊丝熔敷金属,研究Mg含量对其组织和性能的影响。结果表明:熔敷金属主要由α(Al)基体相和少量β(Al_(3)Mg_(2))相组成;熔敷金属层内中心部位以尺寸较小的树枝晶组织为主,近界面处以柱状晶为主,界面区以细小的等轴晶为主;熔敷金属顶部区域为发达的树枝晶结构,Mg出现了晶内偏析,随Mg含量升高,偏析加剧;随焊丝中Mg含量的增高,熔敷金属的抗拉强度和屈服强度提高,而伸长率先增后减,Mg的质量分数为4.49%的熔敷金属综合性能最佳,抗拉强度、屈服强度和伸长率分别为277.7 MPa、131.3 MPa、34.2%。

Ce对Zn-Al-Mg合金镀层组织和耐腐蚀性能的影响

为了考察Ce含量对热浸镀Zn-Al-Mg合金镀层的组织和耐腐蚀性能的影响,采用SEM、EDS、XRD等方法对镀层的形貌、组织成分及物相进行了观察分析,结合盐雾试验对腐蚀产物形貌、组成及含量以及去除腐蚀产物后的镀层形貌进行了分析,并进一步通过电化学测试考察了不同镀层在3.5%NaCl溶液中的电化学行为。结果表明,Zn-5Al-1.5Mg-xCe (x=0, 0.05, 0.10, 0.25,质量分数,%)合金镀层的组织由富Zn相、富Al相和Zn/Al/MgZn_(2)(或Mg_(2)Zn_(11))三元共晶组织组成,少量Ce的加入增加了镀层中三元共晶组织的比例。Ce可以减薄镀层,细化富Al相,提高镀层的均匀性。当Ce添加量为0.10%时,细化效果最好。另外,Zn-5Al-1.5Mg-0.10Ce合金镀层的耐腐蚀性能最好,是Zn-5Al-1.5Mg合金镀层的2.6倍左右。Ce提高了镀层的均匀性,减少了局部腐蚀,提高了Zn_5(OH)_8Cl_(2)·H_(2)O腐蚀产物保护层的均匀性和致密性,从而提高了镀层的耐腐蚀性能。

Investigation of Portevin–Le Chatelier Band Strain and Elastic Shrinkage in Al-Based Alloys Associated with Mg Contents

The Portevin–Le Chatelier(PLC) effect in Al–2.30wt%Mg, Al–4.57wt%Mg and Al–6.91wt%Mg alloys has been investigated at various applied strain rates at room temperature in this study. Three-dimensional digital image correlation(3D-DIC) technique was applied to obtaining the further insight into the spatiotemporal characteristics, in particular the influence of Mg content on deformation behaviors. Mg content has a pronounced effect on serration characteristics, including the serration type and amplitude; Mg content tends to weaken the spatial correlation of the propagative bands. Additionally, the serration amplitude linearly increases with the maximum PLC band strain; high Mg content generates a higher PLC band strain at a given serration amplitude compared with low Mg content. Mg content is found to be effective to enhance the serration amplitude, the maximum PLC band strain and also the amount of elastic shrinkage outside PLC bands.

USING HIGH Mg-CONTENT CORED-WIRE TO SPHEROIDIZE AND DESULPHURIZE DUCTILE IRON MELT IN INDUSTRIAL EXPERIMENTS

Mg-content cored-wire was used to desulphurize and spheroidize ductile iron melt in industrial experiments. The optimal feeding speed and suitable treatment temperature were determined in the experiments. And cored-wire method and pouring method were compared. Conclusions have been drawn that, under these conditions in the experiments, the optimal feeding speed is 15m/min, treatment temperature should be as low as possible, 1400-1450℃ generally; and cored-wire method can act more effective in ductile iron melt desulphurization and spheroid than pouring method.

Mg含量对7A52铝合金MIG焊熔滴过渡及组织性能的影响

用3种不同Mg含量的ER5356铝合金焊丝对20 mm厚7A52铝合金进行MIG焊,研究Mg含量对熔滴过渡及电弧形态的影响,分析不同Mg含量焊丝对7A52焊接接头组织和性能的影响。结果表明:随Mg含量的增加,熔滴尺寸增加,过渡频率降低,焊接电弧产生的压缩作用减弱;焊缝区显微硬度提高,接头的抗拉强度提高,伸长率略有下降,断裂方式为韧性断裂;焊缝区等轴晶尺寸减小,Al_(3)Mg_(2)相增加;熔合区沿晶界处析出的Al_(3)Mg_(2)相增加,晶粒尺寸减小。当Mg的质量分数为5.0%~5.1%时,对裂纹扩展阻力大,焊缝中心延展性较好,抗拉强度为285.33 MPa,综合力学性能较好。

镁含量对高锌Al-9Zn-xMg-1Cu合金时效沉淀相及其强化作用的影响

采用硬度测试和室温拉伸测试,结合透射电镜、高分辨透射电镜及几何相位分析技术,定量研究了Mg含量(1%~3%,质量分数)对高锌Al-9Zn-xMg-1Cu合金在120℃人工时效时沉淀相的影响,并探讨了强化作用。结果表明:当Mg含量从1%增至2%时,合金的屈服强度大幅增加,增加率约为37.7%;当Mg含量继续增至3%时,合金的屈服强度小幅增加,增加率仅为9.1%。Al-9Zn-1Mg-1Cu合金的强化相为η’相,Al-9Zn-2Mg-1Cu和Al-9Zn-3Mg-1Cu合金的强化相都为η’相和T’相。T’相引起的应变大于η’相,其强化效果更好;Mg含量变化对两种强化相引起的最大应变值影响不大。随着Mg含量增加,η’相的体积分数、数量密度及其比例减小,T’相的变化则相反,沉淀相的总数量密度和体积分数增大。基于η’相和T’相的尺寸、体积分数和数量密度,计算和分析了它们对沉淀强化的贡献,计算结果与实验结果基本一致。

Analysis of Mg content of Zn_(1-x)Mg_xO film grown on sapphire substrates by plasma-assisted molecular beam epitaxy

The Mg content of Zn1-xMgxO film grown on A-sapphire substrates by plasma-assisted molecular beam epitaxy is measured by inductively coupled plasma (ICP) and electronic probe microanalysis (EPMA). A theoretical model for analyzing the difference in the Mg content between Zn-rich and Zn-deficient conditions in the growth process is established, and the mathematical relation between Mg content and the temperature of the Mg cell is formulated under Zn-rich condition. The formula derived is proven to be correct by experiments.

Effect of cobalt content on electrochemical performance of La-Mg-Ni system (Ce_2Ni_7-type) electrode alloys

In order to improve the cyclic stability of La-Mg-Ni system (Ce2Ni7-type) alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of (La, Mg)2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% (x=0) to 89.2 % (x=0.2), and then reduced to 87.8 % (x=0.6). After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system (Ce2Ni7-type) alloy electrodes were corrosion and oxidation as well as passivation of Mg and La in alkaline solution.

Effects of magnesium content on phase constituents of Al-Mg-Si-Cu alloys

By means of scanning electron microscopy(SEM), energy dispersive spectrum(EDS), X-ray diffractometry(XRD) and metallographic analysis, the effects of variation of magnesium content on phase constituents of Al-Mg-Si-Cu alloys were investigated. The results indicate that the constituents formed during casting alloys are main Al1.9CuMg4.1Si3.3,Al4(MnFe)3Si2 and Mg2Si, while pure Si is only present in the alloy containing lower magnesium content. Increasing Mg content leads to increasing the amount of Mg2Si, but decreasing the amount of Al1.9CuMg4.1Si3.3 and Al4(MnFe)3Si2. During the following homogenization process, Al1.9CuMg4.1Si3.3 is completely dissolved, Al4(MnFe)3Si2 and pure Si remain unchanged. After rolling and final heat treatment, the constituents in the alloys change no longer.

Mg含量对轨道车辆Al-7Si-xMg铝合金显微组织与力学性能的影响

为改善轨道车辆用Al-7Si-xMg铝合金的显微组织和力学性能,以Al-Si铝合金为基体,通过在凝固过程中进行超声振动制备不同Mg含量的Al-7Si-xMg铝合金,利用光学显微镜(OM)、扫描电镜(SEM)、万能试验拉伸机研究了Mg含量对显微组织和力学性能的影响。Mg元素在Al-7Si-xMg铝合金中主要以Mg2Si相的形式均匀分布在晶界处。随着Mg含量的增大,α-Al相尺寸、长宽比和二次枝晶臂间距先减小后增大,硬度和抗拉强度先增大后减小,伸长率不断减小,当Mg含量达到1.5%时,α-Al晶粒尺寸最小,呈现为椭球状,硬度和抗拉强度最大。Al-7Si-xMg铝合金力学性能的提升是因为细晶强化和Mg2Si颗粒强化的共同作用,过量的Mg导致Mg2Si相粗化,使得力学性能降低。适量的Mg含量可适当改善Al-7Si-xMg铝合金的显微组织和力学性能。

Zn含量对Al-xZn-1.5Mg-1.0Cu合金淬火敏感性的影响

通过浸入式末端淬火与室温拉伸实验,结合相图和时间-温度-转化率(TTT)曲线、差示扫描量热分析及扫描电镜、透射电镜等手段,研究了Zn含量(6.00%~9.08%,质量分数)对Al-xZn-1.5Mg-1.0Cu合金淬火敏感性的影响。结果表明:当淬火速率从200℃/s减小至70℃/s时,Zn含量为8.10%的合金(8Zn alloy)的淬火敏感性最高,Zn含量为6.00%的合金(6Zn alloy)其次,Zn含量分别为7.09%和9.08%的合金(7Zn alloy,9Zn alloy)的淬火敏感性相当且最低;当淬火速率进一步降低时,Zn含量为9.08%的合金(9Zn alloy)的淬火敏感性快速提高;当淬火速率低于约32℃/s时,随着Zn含量从6.00%增加到7.09%,淬火敏感性基本保持不变;然后随着Zn含量从8.10%增加到9.08%,合金的淬火敏感性迅速增加。结合电导率和淬火诱导相面积分数的结果,从淬火诱导相的析出驱动力和形核位置及数量差异的角度,对Zn含量影响淬火敏感性的机理进行了分析讨论。

Fe含量对Al-Mg-Si合金微观组织和力学性能的影响

采用电子拉伸试验机、金相显微镜、扫描电镜、透射电镜等检测手段,研究不同固溶温度下Fe含量对Al-MgSi合金铸棒微观组织和力学性能的影响。结果表明:Fe含量为0.14%(质量分数,下同)时,Al-Mg-Si合金具有最高的强度和断后伸长率,随着固溶温度升高,合金强度不断提高,固溶温度520℃以上时合金强度趋于高点,抗拉强度280 MPa,屈服强度259 MPa,断后伸长率13.40%;时效处理后晶界处富Fe相是球形的α-Al_(8)Fe_(2)Si,对合金基体割裂作用弱,弥散分布在晶界处起到钉扎晶界的作用;当Fe含量低于0.14%时,晶界处球形的α-Al_(8)Fe_(2)Si极少,钉扎晶界弱,在500℃以上固溶时,晶粒明显长大,断后伸长率大幅度降低;当Fe含量高于0.14%时,富Fe相多为长条状的β-Al_(5)FeSi,对界面割裂作用强,随着Fe含量增加,合金强度和断后伸长率不断降低;此外,Fe含量影响β"相时效过程的析出转变,Fe含量为0.14%时,β"强化相析出的尺寸小、数量多、分布密集,对位错运动阻碍作用最强。

Effect of Pb content on the surface topography and corrosion resistance of hot dip Zn-Al-Mg coatings

In this study,the effect of Pb content on the surface morphology and salt spray corrosion resistance of hot dip Zn-Al-Mg coatings was investigated.The results showed that the coating surface easily formed small grains of zinc spangle structures and that the salt spray corrosion resistance of the coating decreased when Pb content was greater than 0.01%.The microstructure and energy dispersive spectrum analysis of surface and cross-sectional areas was performed by scanning electron microscopy.Pb content present in the coating was analyzed by glow discharge spectrum.The results showed that the distribution of Pb in the coating was not uniform.The Pb content was segregated on the surface and at the cross-section of the Zn-Al-MgZn_2 ternary eutectic structure,especially,on the surface of the Zn-Al-MgZn_2 ternary eutectic structure.

热处理对La-Mg-Ni系贮氢电极合金性能的影响(Ⅱ)贮氢及电化学性能

用冷坩埚磁悬浮熔炼方法制备铸态La0.7Mg0.3(Ni0.81Co0.15Al0.04)3.4贮氢电极合金,并分别在1073、1173和1273K温度下热处理8h得到不同的热处理态合金,采用ICP-AES、三电极体系、显微硬度测试、XRD、SEM及EDS等研究合金的Mg含量、电化学性能、显微硬度及相应电极的表面状态。ICP-AES分析表明,合金的Mg含量随着热处理温度的升高而降低。P-C-T曲线显示随着热处理温度的升高,合金放氢平台的平台区域先变宽后变窄,平台压力先降低后升高再降低,平台先变得平坦后倾斜。电化学性能测试表明,合金电极的最大放电容量先增加后减小,循环稳定性先提高后有所降低;其中1173K,8h热处理态La0.7Mg0.3(Ni0.81Co0.15Al0.04)3.4合金具有良好的综合电化学性能,可以用作高容量电极材料。

Mg含量对MgZnO薄膜光学性质的影响

利用射频磁控溅射技术,高纯的氩气作为溅射气体,分别选用不同Mg含量的MgxZn1-xO陶瓷靶材,在石英衬底上生长六角纤锌矿结构的MgxZn1-xO薄膜,并对薄膜进行了后期热退火处理。研究了Mg含量对MgxZn1-xO薄膜光学性质的影响。实验结果显示,随着Mg含量的增加,薄膜的带隙变宽;光致发光光谱中近带边发射中心蓝移,近带边紫外发射与可见光区深能级发射强度比值减小,发光质量下降;拉曼光谱仍然保持着ZnO的拉曼振动模式,但随着Mg含量的增加,E2high振动峰逐渐展宽,峰型对称性变差。分析表明,随着Mg的合金化,薄膜中产生了更多的杂质缺陷,结晶质量下降。

Mg与Ag含量对Al-Cu-Mg-Ag新型耐热铝合金晶间腐蚀性能的影响

采用晶间腐蚀性能测试研究Mg与Ag含量对Al-Cu-Mg-Ag合金抗腐蚀性能的影响,结合透射电子显微分析技术与电化学分析技术等探讨了不同成分合金的晶间腐蚀机理。结果表明:增加Mg与Ag含量能够提高合金的时效硬化速率。随Mg含量的增加,强化相Ω相尺寸逐渐减小,体积分数逐渐增大,晶界析出相增多,无沉淀析出带(PFZ)中溶质原子减少,PFZ与基体的电位差增大,合金的抗晶间腐蚀能力逐渐降低。随Ag含量的增加,合金中的强化相由大量的θ′相和少量的Ω相,逐渐转变为大量的Ω相和少量的θ′相。Ag含量的改变对PFZ的电位差影响不大,合金的耐蚀性主要取决于PFZ的宽度。增加Ag含量能够细化晶界析出相,减小PFZ宽度,腐蚀通道变窄,合金的抗晶间腐蚀性能得到提高。

Al-Cu-Mg高强铝合金的研究进展

综述了Al-Cu-Mg系高强铝合金的发展,评述了微量元素对Al-Cu-Mg系合金性能的影响,介绍了热处理对Al-Cu-Mg系合金的影响机制,指出了现存的问题并展望了Al-Cu-Mg高强铝合金的发展趋势。

微量Mg掺杂对sol-gel制备Zn_(1-x)Mg_xO薄膜结构形貌及其透明导电性的影响

通过sol-gel旋涂法在石英玻璃衬底上制备了不同Mg掺杂含量的ZnO薄膜,并运用XRD、SEM、UV-VIS、四探针等测试手段分析研究了Mg含量对ZnO薄膜结构及透明导电性的影响。结果表明,掺Mg后薄膜仍保持六方纤锌矿结构并沿(002)方向择优生长,随着Mg含量的增加,结晶质量先变好,后变差,(002)峰位先向小角度方向移动,后又往大角度方向回升,薄膜晶粒尺寸变大,尺寸更加均匀,薄膜表面更加平整,当掺杂量增加至3 at%时,薄膜表面开始出现团聚现象;适量的Mg掺杂可提高薄膜可见光透过率和禁带宽度,透过率最高可达88.83%,增加至3 at%时,因散射和缺陷增多,透过率发生显著下降;由于Mg的金属性强于Zn而出现的burstain-Moss效应与缺陷带宽随着Mg含量而变化的共同作用,薄膜带隙出现先宽后窄再变宽的现象;四探针表征显示,Mg掺杂可降低ZnO薄膜的表面电阻,但仍具有较高的电阻率。