Zn含量对AlMgSiCu合金组织和力学性能的影响

使用常规铸锭冶金方法制备了不同Zn含量的AlMgSiCu合金.利用光学显微镜、扫描电镜、拉伸测试和纳米压痕方法研究了Zn含量对铝合金微观组织和力学性能的影响.研究发现Zn元素能够轻微细化AlMgSiCu合金铸态组织.随着合金中Zn含量的增加,铸态铝合金的晶界变宽,晶界析出相增多.Zn的添加未影响铸态合金的相组成和形貌.随Zn含量的增加,铝合金的强度和延伸率呈现先增后降的变化趋势,添加质量分数0.5%Zn可使合金具有最高的强度,而0.75%Zn使合金获得最高延伸率.对含Zn铝合金的纳米压痕测量表明:随着Zn含量的增加,铝合金的弹性模量呈现逐步降低的趋势.      

含Zn3003铝合金的显微组织与性能

采用透射电子显微镜研究了Zn元素对退火态3003铝合金微观组织的影响,并用拉伸试验和电化学极化实验,分别研究了Zn元素对3003铝合金力学性能和电化学腐蚀性能的影响.透射电镜观察和电子拉伸实验结果表明,Zn元素加入3003铝合金,可以细化退火态合金中的析出相,使其分布更加弥散,尺寸更加均匀.Zn元素的加入,可使退火态合...     

采用SECM分析7075铝合金的局部腐蚀行为

使用0.6 mol/LNaCl溶液腐蚀7075铝合金, 采用扫描电化学显微镜进行逼近曲线、面扫描测试, 用X射线衍射仪对合金的形貌进行分析, 用能谱仪分析腐蚀产物成分, 研究7075铝合金局部腐蚀电化学机理.结果显示:逼近曲线呈现正反馈, 探针的电流随着与合金基底距离的减小变大; 合金表面的活性点因为氯离子活化作用不断增加, 形成大范围的点蚀; 氯离子通过吸附在合金表面钝化层并与之反应, 破坏钝化层使得内部裸露, 内部的第2相电极电位更负, 和铝基体构成腐蚀微电池, 第2相的阳极腐蚀溶解降低合金的强度和抗腐蚀能力.      

微量Zn对Al-Cu-Mg合金力学性能及晶间腐蚀的影响

采用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）、电导率测试及常温拉伸实验,结合剥落腐蚀测试、晶间腐蚀测试和电化学测试研究了微量Zn对Al-Cu-Mg合金组织与性能的影响。试验结果表明,微量Zn的添加明显提高了合金T3态（预拉伸+自然时效）的塑性。随着Zn含量的增加,T3态合金点蚀电位提高,S相、阴极相和铝基体之间的电位差减小,点蚀的形成和晶间腐蚀的传播更加困难,合金的晶间腐蚀敏感性降低。     

Cu含量对7xxx系铝合金力学性能及腐蚀性能的影响

文章以添加不同Cu含量(wt.%)(1.4%～2.6%)的Al-Zn-Mg-xCu-Ce-Zr合金为研究对象,通过OM、TEM以及室温拉伸、剥落腐蚀、电化学腐蚀等实验,研究Cu元素对铝合金组织及性能的影响规律。结果表明,随着Cu含量的增加,合金晶内析出相的平均尺寸先减小后增大,合金的力学性能呈先升高后降低的趋势,抗腐蚀性能逐渐降低。当Cu含量为2.2%时,合金晶内析出相的平均尺寸最小且表现出最高的力学性能;当Cu含量为1.4%时,合金表现出最佳的综合性能,抗拉强度、屈服强度和延伸率分别为682MPa、605MPa和13.8%;腐蚀电流密度为1.496×10^-5A/cm²。     

Ti元素对7072铝合金显微组织与性能的影响

通过透射电镜、扫描电镜、拉伸试验和电化学测试等方法,系统研究了Ti元素的添加对模拟钎焊态7072铝合金热传输材料的显微组织、不同条件下力学性能与电化学性能的影响规律.透射电镜分析表明,Ti元素的添加对晶粒尺寸的影响微弱,且对析出相的析出有抑制作用.力学试验结果表明,Ti元素对钎焊态合金的高温力学性能有很大的影响.常温下含Ti合金的拉伸力学性能与无Ti合金相近.但在150℃测试时,屈服强度可提高5.5 MPa,抗拉强度和延伸率基本不变.在200℃测试时,抗拉强度可提高近10 MPa,屈服强度和延伸率略有下降.电化学试验结果表明,添加Ti元素能提高钎焊态7072铝合金的抗腐蚀性能,可使7072铝合金在0.5%NaCl溶液、3.5%NaCl溶液和1M NaCl+0.3M H2O2溶液中的腐蚀电位分别正移8.3mV、11 mV和8.5 mV.     

NH3对CuZnAl合金在3.5%NaCl溶液中腐蚀行为的影响

通过对CuZnAl舍金在3．5％NaCl和3．5％NaCl＋NH，溶液中的腐蚀速率和电化学参数的测试及CuZnAl合金腐蚀形貌的观察，分析了NH3对CuZnAl合金在3．5％NaCl溶液中腐蚀行为的影响。结果表明：NH3能改变CuZnAl舍金的腐蚀形貌，使合金的腐蚀电位负移。腐蚀电流增加，合金的腐蚀速率增大。     

Zn含量对Mg-Mn-Zn合金显微组织和力学性能的影响

通过添加少量的Zn元素制备了(%,质量分数)Mg-2.0Mn-x Zn(x=0,0.5,1.0,1.5,2.0)合金。对合金进行挤压变形,并利用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)等手段,研究了少量的Zn元素对Mg-Mn合金组织及力学性能的影响。实验结果表明,Mg-2.0Mn-x Zn合金的铸态及挤压态组织中主要含有的第二相为颗粒状的α-Mn相,Zn元素均匀固溶于Mg基体中。少量添加的Zn元素可以显著细化铸态Mg-Mn-Zn镁合金的晶粒尺寸。随着Zn含量增加,挤压态合金中动态再结晶区域增加,混晶组织呈减少趋势。少量添加Zn元素对挤压态Mg-2.0Mn合金的强度及塑性都有明显的改善作用,尤其是合金的屈服强度最高增加42%,延伸率增加57%。随着Zn添加量增加,合金强度的增加趋势减弱。SEM观察显示挤压态Mg-2.0Mn-x Zn合金拉伸试样的断口形貌以韧窝及解理台阶为主,呈现韧性断裂与准解理断裂的混合断口形貌。     

Ce含量对Al在3.5％NaCl溶液中腐蚀行为影响的研究

稀土元素及其含量对铝合金耐腐蚀性能的影响及其机制是铝合金开发利用的重要研究课题,采用高频熔炼方法制备Al1-xCex(x=0,0.2％,2.0％(原子分数))合金,通过X射线衍射、金相分析、电化学测试、扫描电镜和能谱等分别对制备的Al1-xCex合金的结构、动电位线性扫描极化曲线、浸泡与电化学腐蚀前后表面形貌的变化进行了研究;对Al1-xCex在3.5％ NaCl溶液中耐腐蚀性能与铈含量的关系进行了系统的分析.结果表明:由于Cl-离子的存在,铝在3.5％ NaCl溶液中发生点蚀破坏;稀土Ce的加入能够细化晶粒,改善合金微观结构,减弱Cl-离子对点蚀的影响;Ce元素在腐蚀表面层富集,有利于形成连续钝化膜,提高合金在NaCl溶液中的耐蚀能力;微量稀土Ce(0.2％)的加入使合金的自腐蚀电位升高,腐蚀电流密度降低,耐腐蚀性能改善明显;但随着Ce含量的增加,即含量高于铈在铝中的溶解度后,铝与铈将形成金属间化合物,基底与金属间化合物相界面的存在使合金的耐腐蚀性能有所降低,Ce含量为0.2％合金的耐腐蚀性能比Ce含量为2.0％的合金要好.所有合金腐蚀后的主要产物为Al2O3.     

Zn及热处理制度对2056铝合金力学性能及局部腐蚀行为的影响

通过拉伸性能测试、晶间腐蚀(IGC)、剥落腐蚀(EXCO)实验、极化曲线测试及透射电镜(TEM)分析,研究Zn元素和不同热处理制度对2056铝合金室温常规力学性能、抗晶间腐蚀性能、抗剥落腐蚀性能及微观组织的影响。结果表明,微量Zn均匀存在于合金的各个位置,可促进S′相的析出和提高合金强度;减小晶内与晶界的电化学腐蚀动力,使晶界析出的S相数量减少并不连续分布,无沉淀析出带(PFZ)变窄,提高合金的抗晶间腐蚀性能和抗剥蚀性能。与T6处理态相比,经T8处理后,晶内析出的S′相数量增加、尺寸减小、分布均匀,合金的强度显著提高,塑性降低;同时,沿晶界析出的S相数量减少,PFZ变窄,合金的抗晶间腐蚀和抗剥落腐蚀能力提高。在3.5%的NaCl溶液中进行的极化曲线测试也表现出相同的结果。     

Influence of the pH of the medium on the anodic behavior of scandium-doped Zn55Al alloy

The anodic behavior of the Zn55Al scandium-doped alloy is investigated. The extreme character of the dependence of the corrosion potential of this material on the content of Sc in it is shown and it is established that an increase in the concentration of chloride ions in the electrolyte promotes a decrease in this characteristics. The pitting-formation and repassivation potential displace to the positive region as the content of the doping elements in the alloys increases, while as the concentration of chloride ions decreases, they shift to the negative region over the entire pH range of the medium. The corrosion rate of the Zn55Al alloy decreases by a factor of 2–3 with the addition of 0.005–0.05 wt % Sc into it, which makes it possible to recommend an alloy of this composition as an anode coating for the anticorrosion protection of steel constructions, wares, and buildings.     

Microstructural control in an aluminum core alloy for brazing sheet applications

The use of aluminum alloys for automotive heat exchangers has increased considerably in the last 15 to 20 years, and in parallel, new alloys have been developed to meet the increased demand for higher strengths and improved corrosion resistance. An Al-Mn alloy, X800, has been developed by Alcan to significantly increase the corrosion resistance of radiator tubes when subjected to typical service environments. Conventional alloy tubes, 3xxx or 6xxx, fail by intergranular attack, whereas X800 utilizes the diffusion of Si during brazing to form a sacrificial layer between core and cladding and thus prevent penetration through the core. The Si penetrates up to a depth of 70 μm into the core alloy and combines with both the Mn in solid solution and the coarse constituent particles to form theα-AlMnSi phase. In contrast to the core, the interface layer exhibits a high dispersoid density, a modified coarse particle chemistry, and a lower Mn level in solid solution after brazing. Three layers remain after brazing; anα-Al residual cladding, the interface layer with a band of dense precipitates (BDP), and the X800 core. Free corrosion potential measurements confirmed the lowering of the potential within the BDP by about 30 mV compared to —710 mV for the brazed X800 core.     

Nb元素对Zr-Ti基生物材料力学性能和耐腐蚀性能的影响

通过真空非自耗电弧熔炼炉制备Zr-Ti-xNb(x=6、8、10,摩尔分数,%,下同)合金,采用锻造和β单相区固溶热处理工艺进一步加工铸锭,通过对材料微观组织、力学性能和耐腐蚀性能的表征,研究Nb元素对Zr-Ti基生物材料力学性能和耐腐蚀性能的影响。结果显示,Zr-Ti-xNb(x=6、8、10)合金均由β相和α″相组成,随着Nb元素含量增加,β相含量增加,α″相含量降低,Nb元素添加提高了合金中β相的稳定性。同时Nb含量增加,合金屈服强度由360 MPa增加至780 MPa,固溶强化效应明显,在变形过程中出现了应力诱发马氏体相变现象,极大提高材料的抗拉强度和塑性。同时可以较好地提高合金的耐腐蚀性能,实验表明三种材料在生理盐水中均表现出较强的耐腐蚀性能。     

固溶温度对挤压态Mg-13Al-6Zn-4Cu合金组织与性能的影响

采用不同的固溶温度对挤压态Mg-13Al-6Zn-4Cu(质量分数,%)合金进行热处理,然后在(150℃/10 h)条件下进行时效处理,通过金相显微镜、扫描电镜及能谱分析、维氏硬度与极化曲线测试,研究固溶温度对挤压态合金显微组织、硬度与腐蚀性能的影响。结果表明:固溶处理促进晶界处的β-Mg_(17)Al_(12)相充分溶入α-Mg基体中。提高固溶温度使基体晶粒再结晶长大,逐渐缩小T-MgAlCuZn相心部的Cu元素富集区,改变β析出相的形态和分布,促进层片状β相在α-Mg晶界析出,从而提高时效态合金的硬度。但固溶温度超过420℃时,合金晶粒粗化并发生过烧。固溶温度升高导致合金腐蚀电位负移,腐蚀电流增大,腐蚀速率加快。     

Influence of Chemical Composition of Mg Alloys on Surface Alloying by Diffusion Coating

A recently developed technique of surface alloying by diffusion-coating has been used to produce coatings on Mg alloys with various Al and Zn contents. The experimental results show that both Al and Zn solutes in the alloy promote the diffusion of alloying elements through grain refinement of the substrate alloys and through reduction of diffusion active energy because of the reduction of melting temperature of the alloys. Therefore, the efficiency of surface alloying increases by diffusion coating. Thick, dense, uniform, and continuous layers of intermetallic compounds, which consist of a τ-phase layer and a β-phase layer, can be produced on the surface of various Mg alloys. The intermetallic compound layers not only have microhardness values that are 4 to 6 times higher than the substrate but also provide effective protection of the Mg alloys from corrosion in 5 pct NaCl solution at room temperature.     

Effects of grain boundary ternary alloy doping on corrosion resistance of(Ce,Pr,Nd)-Fe-B permanent magnets

To satisfy the application of different environments,grain boundary doping is commonly used in the preparation of sintered magnets to improve the coercivity and the corrosion resistance.In this paper,the alloys were prepared by mixing different ratios of the master alloy(Ce,Pr,Nd)-Fe-B and the sintering aid(Pr,Nd)-Al.The coercivity of sintered(Ce,Pr,Nd)-Fe-B magnet is substantially enhanced by doping 2 wt%of(Pr,Nd)-Al,while the maximum energy product decreases slightly.We systematically investigated the corrosion behavior and micro structure of the sintered magnets in order to determine the mechanism of the degradation.The sintered(Ce,Pr,Nd)-Fe-B magnets with 2 wt% of(Pr,Nd)-Al addition exhibit the decreasing corrosion rate compared with others,due to the distribution of intergranular phases.The electrode potential difference between the main phase and the RE-rich phase is reduced by the addition of Al,improving the potential and stability of RE-rich phase due to the higher electrode potential of Al than that of Nd,Pr or Ce.In addition,the element distribution of the magnets doped by(Pr,Nd)-Al indicates that the Al-rich shell formed at the marginal area of the Ce-rich phase improves its stability.Therefo re,intergranular adding te rnary(Pr,Nd)-Al alloy powders results in both high coe rcivity and good corrosion resistance synchronously.     

A New Resource-Saving, High Chromium and Manganese Super Duplex Stainless Steels 29Cr-12Mn-2Ni-1Mo-xN

 A new family of resource-saving, high chromium and manganese super duplex stainless steels (DSSs), with a composition in mass percent, % of Cr 0.29, Mn 0.12, Ni 2.0, Mo 1.0, and N 0.51-0.68, has been developed by examining the effect of N on the microstructure, mechanical properties and corrosion properties. The results show that these alloys have a balanced ferrite-austenite relation. The austenite volume fraction decreases with the solution treatment temperature, but it increases with an increase in N content. The increases in nitrogen enhance the ultimate tensile strength (UTS) and reduce the ductility of the material slightly. The pitting corrosion potential increases first and then decreases with an increase in nitrogen content when the amount of N arrives to 0.68%. The yield stress and ultimate tensile strength of solution-treated samples were more than 680 and 900 MPa, the elongation of experimental alloys are higher than 30%, respectively, what is more, the pitting potentials were beyond 1100 mV.     

Comparison of the Tendency to Pitting Corrosion of Casting of Al6Ca,Al1Fe,and Al6Ca1Fe Experimental Alloys and AK12M2 Industrial Alloy

The electrochemical and corrosion behavior of four alloys (wt %) is investigated: Al–6Ca (further Al6Ca), Al–6Ca–1Fe (further Al6Ca1Fe), Al–1Fe (further Al1Fe), and Ak12M2. An increased iron content (up to 1%) in alloys is necessary for the high productivity of casting under pressure. Electrochemical studies are performed in a 3% aqueous NaCl solution at 26 ± 0.5°C using an IPC-Pro 3A digital potentiostat (IPC-2000). Anodic polarization is performed in a potentiodynamic mode with a potential scan rate of 1 mV/s. The initial polarization potential is–800 mV with respect to the standard hydrogen electrode. The direction of the potential scan was changed to inverse upon the “critical” current density i_cr = 10 mA/cm² performing polarization with the same rate. The tendency of the alloy to form pits was judged by the ratio of amounts of electricity that passed through the electrode before pitting formation and their repassivation (Q_for/Q_inv) and values of pitting resistance bases: the difference in the pitting formation potential and stationary potential and the difference in the repassivation potential and stationary potential. Corrosion tests of casting aluminum alloys were performed holding the samples in a salt fog chamber and in a 3% aqueous NaCl solution for 700 h. After these holdings, the surface morphology of the samples was investigated using an Olympus GX51 optical microscope. It is established that Al6Ca1Fe and Al6Ca experimental alloys, in contrast to the AK12M2 industrial alloy and Al1Fe alloy, are not subjected to pitting corrosion in a 3% aqueous NaCl solution. It is assumed that the increased corrosion resistance of Al6Ca1Fe alloy is caused by the fact that iron enters the Al₁₀CaFe₂ intermetallic compound, which is not an efficient cathode because of the considerable negative potentials of Al and Ca. Due to the high casting and mechanical properties of the Al6Ca1Fe alloy, which are no worse than the properties of eutectic silumin and surpass them by the corrosion resistance, the Al6Ca1Fe alloy is promising for use in an industrial scale.