轧制温度对铝铜锂合金疲劳性能的影响

采用标准紧凑拉伸C(T)试样研究了室温冷轧和350℃温轧的铝铜锂合金固溶时效处理后的疲劳裂纹扩展性能,并采用光学显微镜、扫描电子显微镜、透射电子显微镜和电子背散射衍射对合金微观组织以及疲劳断口进行分析以揭示其内在影响机理。结果表明,固溶时效处理后,室温冷轧板材的再结晶程度比350℃温轧板材高25.3%,裂纹易沿着大角度晶界扩展;温轧板材的疲劳裂纹扩展速率较低,抗疲劳性能较好。

铜碲锂多元合金在3.5% NaCl溶液中腐蚀行为的研究

研究了铜碲锂多元合金中碲对合金耐腐蚀性的影响。经过25℃在 3.5% NaCl溶液中的全浸试验表明铜碲锂多元合金比纯铜具有更好的耐蚀性。利用扫描电镜观察腐蚀试样的表面形貌,发现表面不均匀的覆盖着一层多孔的腐蚀产物。经 X 射线衍射仪分析确定,该腐蚀产物为 Cu2 (OH)3Cl 和 Cu2O 的混合物。

锂对工业纯铜抗腐蚀性能的影响

研究了在工业纯铜中加入微量锂对其抗腐蚀性能的影响。结果表明 :在工业纯铜中加入微量锂会使其在Na Cl饱和溶液中的抗腐蚀性能有所提高 ,但当超过一极限值时 ,其抗腐蚀性能又下降 ,这是由于锂对纯铜的净化效应及对晶粒大小、组织形态及晶格畸变的影响而产生的综合效应所致 ,其主要腐蚀机制是吸氧腐蚀和铜及其它夹杂形成的微电池腐蚀。

锂对工业纯铜导电性能的作用效应

用X光电子能谱仪及同步辐射装置分析了铜锂合金的表面电子结合能及费米面处的电子能态分布.研究表明:微量锂的加入影响了纯铜的价带,使纯铜费米面处的电子态密度下降,从而降低纯铜的导电率,但是由于锂具有良好的脱氧、除硫等净化作用,使纯铜中的其他杂质含量有所下降,因此两者相消后略微降低铜的导电率;随锂含量的增加,铜的导电率呈逐渐下降的趋势,这是因为尽管加入锂后脱气除杂效果显著,但残余的锂主要固溶于铜中,使铜的晶格产生畸变,同时提高了纯铜的表面电子结合能,从而使金属导电率有所下降.

锂对工业纯铜的抗氧化性能的影响

向工业纯铜中加入不同含量的锂能提高其３００ ℃以下的低温抗氧化性， 锂的最佳含量为０ ．０２８８ ％ ， 这是由于在铜的表面生成一种致密度较高的ＬｉＣｕＯ 新相， 阻碍或减缓空气中的氧在铜基体中的扩散所致； 温度较高时其抗氧化性降低， 锂含量越高抗氧化性能越差， 锂易于在氧化膜的缺陷处富集， 严重时会在氧化膜中及铜基体中形成大空洞或连成网状，

深冷轧制与时效处理Al−3.6Cu−1Li合金的显微组织演变和力学性能

对Al−3.6Cu−1Li合金进行室温轧制和深冷轧制,并研究工艺对材料显微组织演变和力学性能的影响。通过显微组织分析与力学性能测试,研究厚度压下率为70%和90%的室温轧制和深冷轧制样品的显微组织和时效特性。经过90%厚度压下率的深冷轧制样品具有高强度和良好的韧性,这主要是由于深冷轧制样品对动态回复的抑制和高密度位错的积累。人工时效研究结果表明,达到峰值硬度的温度与变形量成反比,与轧制温度成正比。此外,明场透射电子显微镜照片表明,时效处理的深冷轧制样品存在T1(Al2CuLi)相析出。研究表明,高存储的应变能增强合金的时效动力学,进而促进强化相形核。

自然时效对Al-Li-Cu-Mg-Zr合金的影响

采用透射电镜 (TEM)和维氏硬度计详细研究淬火后与人工时效前的时间间隔 (自然时效 )对 Al- L i- Cu- Mg合金的影响。研究发现 ,通过在人工时效前引入自然时效可以提高 Al- 2 .4L i- 1.16 Cu- 0 .8Mg- 0 .1Zr(wt% )合金的硬度。合金硬度的增加主要来自于 S相数量的增加和分布更均匀。在人工时效前引入自然时效对 δ′相的尺寸和分布没有影响。

一种Al-Cu-Li合金轧制和时效的力学性能与微观组织演变

研究了深冷轧制(-100℃,-190℃)和热轧(400℃)并随后在160℃时效不同时间的Al-Cu-Li合金带材的力学性能和显微组织。通过透射电子显微镜和X射线衍射检查了动态析出和位错特征。通过超景深显微镜和扫描电子显微镜研究了微观组织和断口表面形貌。与热轧样品相比,经过深冷轧制和时效的样品表现出较高的位错密度和大量的析出物。在-190℃深冷轧制后时效15 h的样品表现出最高的极限抗拉强度(586 MPa),而通过热轧随后5 h时效处理的合金则表现出最高的均匀延展性(11.5%)。析出物的尺寸随着时效时间的增加而增加,这对位错与析出物之间的相互作用机理具有重要影响。过时效时,析出物尺寸比较粗大,拉伸变形过程中位错会绕过析出物进行运动,进而力学性能下降。

Al-Cu-Li系合金热轧板材组织、性能和织构的研究

研究了 Al-Cu-Li-( Mn) -( Zr)合金热轧板在 T8态下的显微组织、性能和织构情况。发现因合金的成分不同 ,T8处理对它们造成的影响也不同。其原因主要是由于 Mn、Zr对合金内部的再结晶过程产生了不同的影响。对热轧板的织构和性能测试结果表明 ,晶体学织构与材料的各向异性之间存在着对应关系 ,材料的塑性各向异性比强度各向异性更为严重 。

Sc对Al-3Cu-1Li合金显微组织和电化学腐蚀行为的影响

用真空熔炼炉制备Al-3Cu-1Li-xSc(x=0、0.1%、0.3%和0.5%)合金,观察合金的显微组织,测量合金的维氏硬度。在0.1mol/L NaCl溶液中,用开路电位(OCP)、极化曲线、电化学阻抗谱(EIS)和Mott-Schottky曲线研究了Sc对Al-3Cu-1Li合金腐蚀行为的影响。结果表明:Sc细化了合金的显微组织,提高了合金硬度;Sc添加后未改变合金的电化学腐蚀机制,该合金热力学稳定性提高的同时耐蚀性有所降低;该合金的耐蚀性与其腐蚀产物膜的载流子密度高低具有相关性。

杂质及Ce含量对Al-Li-Cu-Zr和Al-Li-Mg-Zr合金韧化水平的影响

研究了 Fe,Si,Na,K杂质及 Ce微合金化对 A l-L i-Cu-Zr及 Al-L i-Mg-Zr合金内、外韧化水平的影响 .杂质降低了 Al-L i-Cu-Zr合金的内韧化水平 ,从而降低了其总体韧化水平 .由于 Al-L i-Cu-Zr合金中添加微量 Ce可明显提高材料的内韧化水平及抑制杂质的脆化作用 ,故可改善合金的断裂韧性 .对于Al-L i-Mg-Zr合金 。

Li对工业纯Cu的变质效应研究

在真空保护气氛下 ,熔炼不同锂加入量的铜锂合金 ,用扫描电镜及图像分析仪分析其晶粒大小。结果表明 ,微量锂增大工业纯铜的晶粒尺寸 ,且随锂含量的增加 ,其晶粒尺寸亦随之增大 ,增至一定值后其晶粒尺寸又随锂含量的增加而减小 ,这主要是由于锂加入量的改变引起晶体核心形核率的变化所致。

Exfoliation corrosion of T6- and T8-aged Al_xCu_yLi_z alloy

The exfoliation corrosion behavior of a novel Al-Li alloy treated by T6- and T8-peak ageing was studied by electrochemical impedance spectroscopy(EIS) technique. The surface morphology of corroded samples was examined by scanning electron microscope(SEM). The microstructure of un-corroded samples was observed by transmission electron microscope(TEM). At early stage of immersion in EXCO, EIS plots of the two differently processed samples are composed of a capacitive arc in the high frequency range and an inductive loop in the low frequency range. Inductive loop disappears with the increasing of immersion time and two capacitive arcs appear. T6-treated alloy has higher exfoliation susceptibility than T8-treated one, suggested by different exfoliation starting time, which is 23 h and 27 h respectively. T1 phase and equilibrium precipitate at the grain boundary of T6-treated alloy are larger in amount and size than those of T8-treated alloy. This is the main reason for the higher exfoliation susceptibility of T6-treated alloy.

Calculation of free energy of Al-Cu-Li alloy under electric field

Based on Thomas-Fermi model, the interior potential boundary condition with the effect of electric field was defined, the calculation method of free energy for atom cluster under electric field was established. The change of free energy of Al-Cu-Li alloy under the effect of electric field was calculated quantitatively. It is shown that: near the zero electric field and the side of positive electric field, the free energy of Cu4LiAl7 compound at aging temperature 460 K is higher than that of free energy at solid solution temperature 725 K, but once the negative electric field increases to certain degree there will be opposite result. Under the effect of electric field, at 725 K the free energy of Cu4LiAl7 is higher than that of Al-1.0%Li-4.0%Cu, and at 460 K the free energy of compound is lower than that of solid solution. When the copper content in the Al-Li-Cu solid solution is below 5%, under the effect of electric field the free energy of solid solution increases gradually with the increasing of copper content, but the increasing amplitude reduces with the increasing of copper content. The free energy of binary solid solution increases with the addition of lithium, and with the increasing of electric field intensity the free energy margin of two kinds of solid solution becomes bigger.

Flow stress behavior of Al-Cu-Li-Zr alloy containing Sc during hot compression deformation

The flow stress behavior of Al-3.5Cu-1.5Li-0.25(Sc+Zr) alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermal-mechanical simulator. Compression tests were preformed in the temperature range of 653-773 K and in the strain rate range of 0.001-10 s-1 up to a true plastic strain of 0.7. The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature,and decreases with increasing temperature at a given imposed strain rate. The relationship between the flow stress and the strain rate and the temperature was derived by analyzing the experimental data. The flow stress is in a hyperbolic sine relationship with the strain rate,and in an Arrhenius relationship with the temperature,which imply that the process of plastic deformation at an elevated temperature for this material is thermally activated. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of n,α and A in the analytical expressions of flow stress σ are fitted to be 5.62,0.019 MPa-1 and 1.51×1016 s-1,respectively. The hot deformation activation energy is 240.85 kJ/mol.