淬火速率对7020铝合金板材耐剥落腐蚀性能的影响

通过剥落腐蚀浸泡实验、电化学阻抗谱技术,并结合电子背散射衍射技术、扫描电镜以及扫描透射电镜等分析手段,研究了淬火速率对7020铝合金板材剥落腐蚀性能的影响。结果表明:淬火速率从1800℃/min下降到38℃/min时,合金耐剥落腐蚀性能降低,腐蚀等级由EA级变为EB+级,最大腐蚀深度从388μm增加至570μm。通过分析晶界析出相的数量、尺寸、间距及其化学成分和无沉淀析出带宽度的变化来探讨淬火速率对剥落腐蚀的影响机理。     

冷却速率对Al-Zn-Mg-Cu合金厚板剥落腐蚀的影响

研究了冷却速率对Al-Zn-Mg-Cu合金厚板剥落腐蚀性能的影响。结果表明,降低冷却速率,合金的剥落腐蚀性能随之下降,腐蚀等级由EB级变成ED级,腐蚀电极电位更负,电流密度增加,极化电阻减小且与冷却速率呈线性关系。冷却的速率降低导致晶界析出相覆盖率增大,晶界析出相的Cu含量降低和晶界无沉淀析出带宽化是剥落腐蚀性能下降的主要原因。     

新型Al-Mg合金的耐腐蚀性能

采用晶间腐蚀、剥落腐蚀实验结合扫描、透射电镜等手段观察分析腐蚀后合金的微观形貌和相结构,研究了合金元素和热变形工艺对新型Al-Mg合金的抗晶间腐蚀和剥落腐蚀性能的影响。结果表明:随着Mg含量的增加合金在浓硝酸溶液中的腐蚀失重量增大,抗晶间腐蚀性能降低;合金中Zn含量的的提高导致在晶界上形成了不连续析出的Mg32(Al,Zn)49相,降低了合金的腐蚀失重量,提高了Al-Mg合金的抗晶间腐蚀性能。合金的抗腐蚀性能也受形变热处理工艺的影响,对冷变形后的合金进行适当的稳定化处理,相比单纯的冷变形可同时提高合金的抗晶间腐蚀性能与剥落腐蚀性能。冷变形后的残余应力、高位错密度以及拉长晶粒形貌都导致更多的析出相在晶界连续析出,形成网状膜,使合金的抗腐蚀性能降低。     

Al-Mg-Sc合金的剥落腐蚀性能

采用目视剥落腐蚀敏感性试验考察了微量Sc对Al-Mg合金剥落腐蚀性能和力学性能的影响，不同Mg,Sc含量的Al-Mg合金的剥落腐蚀及力学性能测试表明，合金的剥落腐蚀性能与合金的Mg含量和热处理工艺有很大的关系，Mg含量低于5．5％时合金有很好的抗剥落腐蚀性能，随着Mg含量的增加，合金的强度上升，稳定化温度提高使合金的强度下降，冷加工使合金出现了（220），（311）织构。     

7085铝合金剥落腐蚀的淬火敏感性

采用末端淬火实验、剥落腐蚀实验结合扫描和透射电镜分析,研究了7085铝合金剥落腐蚀的淬火敏感性。结果表明:7085铝合金的耐剥落腐蚀性能随淬火速率的降低而下降,腐蚀等级由EA级变为EB级,最大腐蚀深度从135μm增加至315μm,腐蚀深度与淬火速率的对数呈线性关系。淬火速率降低导致晶界析出相尺寸增加、无沉淀析出带宽化和在亚晶处也有η相析出,是造成剥落腐蚀淬火敏感性的主要原因。     

微量Zr对Al-Zn-Mg-Mn合金板材抗剥落腐蚀性能的影响

通过腐蚀浸泡实验和电化学阻抗谱测试,研究了微量Zr的添加对Al-Zn-Mg-Mn合金板材抗剥落腐蚀性能的影响,并结合金相显微镜(OM)、电子背散射衍射技术(EBSD)、扫描透射电镜(STEM)等显微组织表征结果对影响机理进行分析和讨论。结果表明：在Al-Zn-Mg-Mn板材中添加微量Zr可以改善抗剥落腐蚀性能,剥落腐蚀等级由EB级变为EA级,最大腐蚀深度由593 μm降至421 μm。通过分析板材晶粒组织的差异和晶界η相尺寸、间距和化学成分的变化及无沉淀析出带宽度的变化,认为添加微量Zr后是通过综合作用来影响材料的剥落腐蚀行为。     

Fe含量对Al-1.04wt.%Mg-0.64wt.%Si-0.23wt.%Cu合金析出相、力学性能和腐蚀性能的影响

Fe含量对于铝合金的熔炼成本、成形性能和使用性能具有重要影响,本文研究了 Fe含量(质量分数)对AlMg1SiCu合金析出相、力学性能和腐蚀性能的影响,并探讨了 Fe含量对性能的影响机制.结果表明,随着Fe含量由0.27％增加至1.44％,试样中的主要富铁相变化规律为:针状β-Al9Fe2Si2 →汉字状α-Al17 Fe3.2 Mn0.8 Si2 →短棒状Fe2Al3Si3.Fe含量由0.27％增加到1.21％时,试样的平均晶粒尺寸由173 μm减小到122 μm,继续提高Fe含量则平均晶粒尺寸增大.在本文Fe含量范围内,试样的屈服强度基本不变,但抗拉强度和断后伸长率随着Fe含量的增加而显著增加,当Fe含量超过1.21％时略有下降,其原因与富铁相的变化规律有关.试样的腐蚀速率与试样中主要富铁相的种类和数量有关,试样的自腐蚀电位随着Fe含量的增加先增大后减小,腐蚀电流随着Fe含量的增加逐渐增大.综合考虑力学和腐蚀性能因素,AlMg1SiCu合金合适的Fe含量约为0.50％.     

Gd对Mg-x Gd-1Er-1Zn-0.6Zr合金显微组织和腐蚀行为的影响EI北大核心CSCD

采用重力铸造法制备Gd含量分别为7%(质量分数,下同),9%和11%的Mg-x Gd-1Er-1Zn-0.6Zr合金,利用光学显微镜、扫描电镜和X射线衍射仪等研究合金的显微组织,通过开路电位、动电位极化和电化学阻抗测试等方法研究合金在3.5%NaCl溶液中的腐蚀行为。结果表明:当Gd含量从7%增至11%时,开路电位峰值时间从1609 s降为851 s,电荷转移电阻从588.5Ω降至31.9Ω,腐蚀电流密度从2.21×10^(-5)A/cm^(2)增至3.97×10^(-5)A/cm^(2),说明随着Gd含量的增加,合金耐蚀性下降,这主要归因于第二相的微电偶腐蚀效应和腐蚀屏障效应共同作用。当Gd含量从7%增至11%时,(Mg,Zn)_(3)(Gd,Er)相体积分数从1.9%增至5.2%,并从沿晶界不连续分布转变为半连续分布,层片状LPSO相体积分数从11.7%增至26.7%,并沿着晶界贯穿晶粒内部,(Mg,Zn)_(3)(Gd,Er)相和层片状LPSO相体积分数的增加导致合金耐腐蚀性能下降,但大量细小层状LPSO相也能阻止腐蚀扩展,使得Gd含量为11%的合金在8~24 h内腐蚀速率增长减缓。     

Fe含量对Ti80合金显微组织和性能的影响

研究了不同Fe元素含量（0.04%~0.41%,w）对Ti80合金显微组织和性能的影响。结果表明:增加Fe含量,可以提高Ti80合金室温强度。Fe元素含量每增加0.2%,合金强度提高约20 MPa,但对合金塑性与冲击性能无明显影响。Fe元素对合金组织形态有影响,当Fe含量提高至0.41%时,α相由球状转变为长条状。30 d海水腐蚀试验周期内,Fe元素的加入降低了Ti80合金的开路电位,导致合金在天然海水浸泡和5 m/s流速条件下平均腐蚀速率增大,耐海水腐蚀性能有所下降,但与正常Ti80合金仍处于同一数量级。      

固溶前深冷变形处理对7050铝合金组织和性能的影响

本工作提出了7050铝合金自由锻件深冷变形新工艺,即在热处理前将合金置于液氮中,待合金降至液氮温度后进行单道次压缩变形。经热处理后,采用硬度仪、室温拉伸、电导率、晶间腐蚀、剥落腐蚀测试及金相显微镜、扫描电镜和透射电镜研究了不同深冷变形量对7050铝合金微观组织、力学性能和抗腐蚀性能的影响。结果表明:随着深冷变形量的增大,合金再结晶比例上升,晶粒逐渐细化,晶界析出相间距减小,由非连续分布转变为连续分布,晶界无析出带宽度变窄;合金的抗拉强度、屈服强度与硬度明显升高,最大提升幅度分别为33 MPa、35 MPa和10. 5HV,延伸率最大提升幅度为1. 5%;电导率呈现小幅下降趋势,合金抗晶间腐蚀和抗剥落腐蚀性能降低,30%深冷变形量对应的晶间腐蚀最大深度为167μm,剥落腐蚀等级为EC。     

Influence of aging temperature on corrosion behavior of Al–Zn–Mg–Sc–Zr alloy

Al–Zn–Mg–Sc–Zr alloy sheets were prepared using water chilling copper mould ingot metallurgy processing which was protected by active flux. The effect of aging temperature on the corrosion characteristics of Al–Zn–Mg–Sc–Zr alloy was investigated by means of exfoliation corrosion testing, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) combined with transmission electron microscopy, scanning electron microscopy and optical microscopy observation. It is found that with increasing the aging temperature the susceptibility to exfoliation corrosion decreases. Electrochemical measurements reveal that at early stage of immersion in testing solution, EIS plots of the samples are composed of a capacitive arc and an inductive loop. Inductive loop disappears with the increasing of immersion time and two time constants in impedance diagrams appear. Moreover, the trends of corrosion resistance are further confirmed by polarization curve and EIS test. In addition, transmission electron microscopy observations show that the improved corrosion resistance from increasing aging temperature is duo to the coarsening of matrix and separated precipitates at the grain boundary, and the increased spacing of grain boundary precipitates.     

Al-Zn-Mg合金T4板材微观组织对剥落腐蚀性能的影响

采用剥落腐蚀、金相和SEM-EBSD方法研究了Al-Zn-Mg合金T4板材的基体组织与剥落腐蚀性能的关联性。研究结果表明,Al-Zn-Mg合金的剥落腐蚀裂纹主要沿晶界扩展,抗剥落腐蚀深度与Al-Zn-Mg合金T4板材基体组织中的亚结构组态有关,亚结构所占比例小的板材,其抗剥落腐蚀性能优于亚结构所占比例大的。     

Corrosion resistance of Al–Li alloys

Abstract

Experiments designed to investigate the corrosion resistance of several lithium-containing aluminium alloys are described. Intergranular corrosion was investigated using the NAWL test, exfoliation corrosion using the EXCO test, and stress corrosion using the C-ring test. It was found that intergranular corrosion varied with extrusion parameters and was more severe in copper-containing alloys. Alloys containing less than 0·4% Cu were not susceptible to stress corrosion. In alloys that failed, susceptibility increased as the aging treatment was extended from the underaged to the peak aged temper and also with increasing copper content. The addition of copper to ternary Al–Mg–Li alloys also increased the exfoliation corrosion attack.

MST/494     

医用Mg-Zn-Ca-Mn合金在PBS模拟体液中的腐蚀行为

利用真空感应熔炼,采用金属模浇铸制备了Mg(100-x-y-z)-Znx-Cay-Mnz四元合金。使用光学显微镜、X射线衍射仪、扫描电镜及能谱仪对合金进行分析和表征。探讨了合金在PBS模拟体液中的腐蚀行为。结果表明,Ca、Zn及Mn原子的复合加入可显著细化合金的铸态显微组织;镁合金的腐蚀发生于晶粒内部,至晶界处终止;当加入2.0%的Zn和0.5%的Ca时,铸态合金的抗腐蚀性能最佳(平均腐蚀速率为0.77mm/a);当Zn、Ca含量均大于1%时,固溶时效态合金的腐蚀速率下降为铸态的1/2～1/4,表现出优异的耐蚀性;固溶时效处理可有效减少Mg2Ca相的体积分数,改善其分布,提高合金的耐蚀性能。     

Effect of rare earth metals on microstructure and corrosion resistance of Zn–0·18Al coatings

Abstract

Effect of rare earth (RE) metals addition on the microstructure, formation of Fe–Zn intermetallics and corrosion resistance of the batch galvanising Zn–0·18Al coating were studied. Microstructure of the coating was observed using optical microscopy, scanning electron microscopy and transmission electron microscopy. Salt spray test and surface potential measurement were employed for corrosion resistance determination. The results show that the addition of RE can improve bath liquidity, refine surface spangles, stabilise the Fe₂Al₅ inhibition layer, decrease coating thickness and enhance corrosion resistance of the coating. However, corrosion resistance of the coating did not increase continuously with increasing RE content and the optimum RE content lies between 0·045 and 0·069% in the experiment. Mechanism of RE on the corrosion resistance of the galvanised coating was briefly analysed.     

Mn和Zr对Al-Zn-Mg-Cu铝合金各向异性的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)以及室温拉伸、剥落腐蚀、晶间腐蚀等测试方法,研究了微量的Mn和Zr对Al-Zn-Mg-Cu铝合金的组织和性能各向异性的影响。结果表明,在Al-Zn-Mg-Cu-Ti合金中,分别添加微量的Mn和Zr,合金中对应析出细小弥散的Al6Mn和Al3Zr相,这两相均能抑制基体再结晶,促使合金的晶粒纵横比增大。合金的力学性能、抗晶间腐蚀和剥落腐蚀性能提高,但性能各向异性增大。同时,结果显示Zr对合金的组织和性能各向异性的影响显著大于Mn。     

Influence of Si,Ca and Ag addition on corrosion behaviour of new wrought Mg–Zn alloys

Abstract

The development of new wrought magnesium alloys for automotive industry has increased in recent years owing to their high potential as structural materials for low density and high strength/weight ratio demands. However, the poor mechanical properties and low corrosion resistance of the magnesium alloys have led to searching a new kind of magnesium alloys for better strength, ductility and high corrosion resistance. The main objective of the present research is to investigate the mechanical properties and the corrosion behaviour of new magnesium alloys, Mg–Zn–Ag (ZQ) and Mg–Zn–Si–Ca (ZS) alloys. The ZQ6X and ZS6X–YCa alloys were prepared by using hot extrusion method. Hardness AC and DC polarisation tests were carried out on the extruded rods, which contain different amounts of silver or silicon and calcium. The potential difference in air between different phases and the matrix was examined using scanning Kelvin probe force microscopy. The microstructure was examined using optical and electron microscopy (TEM and SEM), X-ray analysis and EDS. The results showed that the silver addition improved the mechanical properties but decreased the corrosion resistance. The addition of silicon and calcium also affected both mechanical properties and corrosion behaviour. These results can be explained by the effects of alloying elements on microstructure of Mg–Zn alloys such as grain size and precipitates caused by the change in precipitation and recrystallisation behaviour.     

Korrosionsverhalten der Legierung Al-Li-Cu-Mg

Corrosion Behaviour of the Al-Li-Cu-Mg Alloy The localized corrosion behaviour of the Al-Li-Cu-Mg alloy 8090-T651 (25 mm thick plate) was investigated using salt spray tests, EXCO tests and tests according to the MIL-H-6088F specification. These accelerated laboratory tests indicate that the material is susceptible to intergranular and exfoliation corrosion. The stress corrosion cracking behaviour was studied under constant load, constant deformation and slow strain rate conditions. The material was found to be resistant against stress corrosion cracking in the long transverse direction. In the short transverse direction a threshold stress below 50 MPa was determined. The same values were measured for the conventional alloys 2014-T351 and 2024-T351. The fracture surfaces of specimens failed due to stress corrosion cracking were examined using a scanning electron microscope. Fractographic features attributed to corrosion were discussed.     

7075铝合金无铬磷化成膜动力学过程及其性能

直接在7075铝合金表面喷涂油漆,其结合力和防护性能较差。先对7075铝合金作磷化处理再喷涂环氧底漆和聚氨酯面漆。应用X射线衍射仪、Autolab电化学工作站和扫描电子显微镜及加温耐盐水试验对磷化膜的物相组成、成分、表面形貌及其耐蚀性进行了研究;探讨了磷化处理对7075铝合金表面漆膜层结合力及耐腐蚀性能的影响。结果表明:7075铝合金表面磷化动力学过程分为基体阳极溶解、表面形核及膜层增厚3个阶段,主要得到了由Mn Zn2(PO4)2,Zn3(PO4)2,Al PO4等物相组成的多孔磷化膜; 7075铝合金表面的自腐蚀电流由磷化前的40.17μA/cm^2降低到磷化后的7.37μA/cm^2,磷化提高了其耐点蚀性能;磷化处理还极大地提高了漆膜与7075铝合金的附着力和耐腐蚀性。