Zr对Al-Li合金晶粒细化作用的电子理论分析

运用固体经验电子理论(EET),对Al-Li-Zr合金的价电子结构进行计算.结果表明:Zr与Al原子存在强烈的相互作用,在固溶体中形成Al-Zr偏聚区.Al-Zr原子的偏聚析出的细小Al3Zr粒子,均匀弥散分布在基体中,起到抑制晶粒长大,细化Al3Li晶粒的作用.Al3Zr和Al3(Zr,Li)粒子具有较强的Al-Zr共价键,不易被位错的切割折断,因而对位错的运动有较大的阻力,对合金起到强化作用.另一方面,共格复合相Al3(Zr,Li)的析出,可以降低共格界面错配度,使得界面键合强度分布较均匀,对提高基体的韧性是有益的.     

微量Er、Zr对Al-1.5Mg合金微观组织和性能的影响

借助OM、XRD和SEM等手段研究了微量Er、Zr元素对Al-1.5Mg合金微观组织和性能的影响。结果表明:合金中除了含有少量的β相(Mg2Al3)和Mg2Si外,绝大部分为铁基相(Al3Fe和Al12Fe3Si);复合添加Er、Zr能促进铁基相析出,实现针状相转化为相对无害的骨骼状相,提高了合金的宏观硬度和加工性能;大部分Er溶解在Al基体中,其余分布在晶界处的Er易吸附固/液界面前沿处的铁等原子,造成成分过冷,从而增加形核率,细化晶粒;Zr几乎都固溶于Al基体中,但有少量Al3Zr粒子形成。     

Ni-Al-Re/Ru合金的层错能

使用置换原子计算层错能的热力学模型计算了Ni-Al-Re(Ru)合金的层错能,研究了合金元素和温度对层错能的影响.结果表明:随着温度的提高,Ni-Al-Re(Ru)合金的层错能增加.Ni-6?-4%Re合金的层错能随着温度的提高线性增加.Ni-6%Al-4%Ru合金的层错能,在温度低于500℃时随着温度的提高呈抛物线规律增加,高于500℃时随着温度的提高呈线性规律增加.Al原子可明显降低Ni-6%Al-4%Re(Ru)合金的层错能.随着Al含量的提高,原子偏聚自由能(ΔGγ→εs)降低,使Al原子自发偏聚,并促进γ'有序相的形成和数量的增加,是合金层错能降低的主要原因.而Ru原子降低合金的偏聚自由能,可提高γ'有序相的稳定性.随着温度的升高,原子偏聚引起的自由能(ΔGγ→εs)增加可抑制原子偏聚;当温度高于500℃时,含Ru合金有比Ni-Al-Re合金高的原子偏聚自由能(ΔGγ→εs),故元素Ru能抑制原子的偏聚和TCP相的析出.     

Al-Mg-Mn和Al-Mg-Mn-Sc-Zr合金的再结晶

研究了Al-Mg-Mn和Al-Mg-Mn-Sc-Zr合金冷轧后在不同退火温度下合金的组织和性能的变化.结果表明,与不添加钪和锆的合金相比,复合添加0.4%Sc(质量分数)和Zr能使Al-Mg-Mn合金的再结晶开始温度提高120℃左右.添加微量Sc和Zr合金没有明显再结晶终了温度,在接近熔点时显微组织仍是加工态纤维组织.Sc,Zr复合添加形成的纳米级的二次Al3(Sc,Zr)相质点,对位错和亚晶界有强烈的钉扎作用,再结晶难以形核和长大,从而有效地抑制冷轧后退火过程中的再结晶.     

Zr_(50-x)Cu_(50)Al_x(x=0～25)合金中的二十面体团簇以及Al添加对非晶形成能力和结构转变的影响

采用X射线衍射(XRD)和扫描电子显微镜(SEM)技术研究了Al元素的添加以及二十面体团簇结构对不同冷却速率下Zr50-xCu50Alx(x=0～25)合金的非晶形成能力、合金结构以及相变过程的影响。结果表明,对直径3mm的Zr45Cu50Al5合金,其主相为ZrCu和二十面体相,而对于直径为3mm的Zr45Cu50Al5合金,其主相则为ZrCu和非晶相。二十面体相的衍射峰强度随着冷却速率的增加而大大降低,直至变成弥散峰。反映出二十面体相与非晶相之间存在强烈的关联性。Zr-Cu-Al合金中的非晶相与二十面体相具有相同的短程有序结构,即二十面体团簇结构,这种5次对称的原子堆垛结构与周期性有序的晶体结构互不相容,从而起到阻碍结晶、提高非晶形成能力的作用。     

时效处理对Al-Zr-Sc(-Er)合金组织和性能的影响EI北大核心CSCD

通过透射电镜(TEM)和扫描透射电镜(STEM)以及硬度、电导率测试等方法系统研究了时效处理对Al-Zr-Sc三元合金以及Al-Zr-Sc-Er四元合金显微组织和性能的影响。结果表明:对于Al-Zr-Sc合金,增加Sc含量,可显著提高合金时效响应速率、峰值硬度和热稳定性;增加Zr含量,显著提高了合金硬度和热稳定性,但会降低电导率。在Al-Zr-Sc合金中添加Er,进一步提高了合金的时效响应速率,促进了Zr,Sc的脱溶析出。Er与Zr,Sc形成具有核-双壳结构的Al 3(Er,Sc,Zr)相,明显改善合金的硬度和电导率。经300℃单级时效,实验合金硬度较高,但电导率相对较低;经400℃单级时效,实验合金时效响应速率加快,电导率明显提高,但硬度显著下降;经300℃/24 h+400℃的双级时效实验合金可获得电导率、强度和热稳定性的良好匹配。     

快速凝固高温铝合金显微组织及热稳定性研究

本文研究了快速凝固Al90.5Fe4.0Cu2.0Ce1.0Zr0.5Ti0.5V0.4Si1.1(at%)高温铝合金的显微组织及其热稳定性.结果表明,合金存在三种基本组织,即胞晶和显微胞晶组织、共晶组织、弥散析出相.350℃等温退火后,胞晶组织发生分解,弥散强化相Al12(Fe,V)3Si和Al17Cu5Ce2Fe的数量明显增多,并有一定数量的Al3(Zr,Ti)相析出.400℃以上温度热处理时,弥散相Ai17Cu5Ce2Fe发生部分分解,形成Al7Cu2Fe相.     

Er对汽车框架用铝合金组织与性能的影响

对比分析了不同退火温度下不含Er和含Er铝合金显微组织、显微硬度、拉伸力学性能和断口形貌的变化规律。结果表明,在相同退火温度下,含Er铝合金的显微硬度都要高于不含Er铝合金;相同的退火温度下,含Er铝合金的抗拉强度和屈服强度都要高于不含Er铝合金;含Er铝合金相对不含Er铝合金的再结晶温度有明显提高,这主要与合金中Er元素添加后形成了与基体保持共格或者半共格关系的纳米级Al_3Er或者Al_3(Zr,Er)粒子有关。     

铝铜合金的晶界偏析行为及析出相的理论研究

晶界偏聚行为及析出相形成对铝铜合金的力学性能提升至关重要.为研究铝铜合金中Cu元素与Al基体的相互作用,本文基于密度泛函理论,利用第一性原理方法计算了 Al∑5(210)[001]晶界Cu元素的偏析能、电荷密度分布等性质,并结合AFLOW的高通量框架系统研究了不同铝铜二元析出相的晶格常数、形成能和弹性常数等信息.晶界模...     

Zr含量对铸造AlSi7Mg0.4合金力学性能的影响

研究了添加Zr元素的重力铸造AlSi7Mg0.4合金的微观组织和力学性能.结果 表明,在含Zr的铸态合金中生成了(Al,Si)3(Zr,Ti)和π-Fe相,Zr的添加使合金的晶粒尺寸减小;经过T6热处理后富Fe相中的Mg和少量粗大的(Al,Si)3(Zr,Ti)相重溶到基体中,减小了金属间化合物的尺寸,生成了与基体有共...     

Atomic bonding and mechanical properties of Al–Li–Zr alloy

The atomic bonding of Al–Li alloy with minor Zr is calculated according to the “Empirical Electronic Theory in Solids”. The result shows that the stronger interaction between Al and Zr atoms, which leads to form the Al–Zr segregation regions, promotes the precipitation of Al₃Zr particles and produces a remarkable refinement of Al₃Li grains in the alloy. Because there are the strongest covalent Al–Zr bonds in Al₃Zr and Al₃(Zr, Li) particles, these covalent bonds can cause a great resistance for dislocation movement, and is favorable to strengthen the alloy. On the other hand, with precipitating the Al₃(Zr, Li) particles, it causes the coherent interphase boundary energy of Al/Al₃Li to decrease, and atomic bonding is well matched in between the interface of two phases.     

Coarsening kinetics and strengthening mechanisms of core-shell nanoscale precipitates in Al-Li-Yb-Er-Sc-Zr alloy

The tailored nanoparticles with a complex core/shell structure can satisfy a variety of demands, such as lattice misfit, shearability and coarsening resistance. In this research, core-shell nanoscale Al3(Yb, Er, Sc,Zr, Li) composite particles were precipitated in Al-2 Li-0.1 Yb-0.1 Er-0.1 Sc-0.1 Zr(wt%) alloy through the double-aging treatment, in which the core was(Yb, Er, Sc, Zr)-rich formed at 300°C and the shell was Li-rich formed at 150°C. The coarsening kinetics and precipitate size distributions(PSDs) of Al3(Yb, Er, Sc,Zr, Li) particles aged at 150°C previously aged at 300°C for 24 h showed a better fit to the relation of 2∝ kt and normal distribution, indicating that the coarsening of precipitates was controlled by interface reaction, not diffusion. The Orowan bypass strengthening was operative mechanism at 150°C.     

Zr+Er及Zr+Y对Al-Mg-Si-Cu-Mn-Cr合金组织和拉伸力学性能的影响

采用光学显微镜(OM)、电子显微镜(SEM)、能谱分析仪(EDS)、透射电子显微镜(TEM)和拉伸强度试验研究了0.3%Zr+0.2%Er和0.3%Zr+0.2%Y(质量分数)两种元素组合对Al-0.6Mg-0.9Si-0.5Cu-0.5Mn-0.2Cr合金热处理前后微观组织和力学性能的影响。研究结果表明,两种元素组合的加入均能细化铸态晶粒,其中Zr+Y改性合金的晶粒细化更明显,且两种改性合金铸态的强度和塑性均较基体合金提高。在热处理过程中,两种元素组合会影响合金中弥散相的析出,降低合金的弥散强化效果。最终,Zr+Er改性合金的强度较基体合金提高,而Zr+Y改性合金的强度则较基体降低,两种合金的塑性均较基体降低。     

Effect of Zr on microstructure and mechanical properties of the Al–Cu–Er alloy

ABSTRACT

The microstructure and mechanical properties of the Al–4Cu–2.7Er–0.3Zr alloy were investigated. The precipitates of the L1₂ structured phase with sizes 37?±?12?nm were formed in lines and homogenously distributed inside the aluminium matrix after annealing at 605°C for 1?h. The as-rolled Al–4Cu–2.7Er–0.3Zr alloy developed an increased hardness after 1?h annealing at 100–550°C and 0.5–6?h annealing at 150–250°C due to precipitation of the Al₃(Er,Zr) phase. Addition of Zirconium improved the tensile properties relative to those of the Zr-free alloy by approximately 20?MPa: yield strength?=?273–296?MPa and ultimate tensile strength?=?296–328?MPa in the alloys annealed at 100–150°C.     

Phase equilibria and crystal structure of ternary compounds in Al-rich corner of Al-Er-Y system at 673 and 873 K

Phase equilibria in the Al-rich corner of the Al-Er-Y ternary system from 65 at.% to 100 at.% Al at 673 and873 K were investigated,and the two isothermal sections were established by X-ray diffraction(XRD),scanning electron microscope(SEM) and electron probe micro analysis(EPMA).Three ternary-phase regions are observed and the phase relations are similar at both isothermal sections.There are two ternary compounds,and a complete crystal structures and composition ranges of the two ternary compounds are determined as τ₁(Al_75-76Er_15-22Y_2-10,R-3 m) and τ₂(Al_75-76Er_11-17Y_7-14,P6₃/mmc) via XRD,focused ion beam coupled with transmission electron microscope(FIB-TEM) and EPMA.Meanwhile,the solubilities of the third element in the binary compounds at both temperatures are measured.The solubility of Er inβ-Al₃ Y phase reaches to 6.6 at.% and that of Y in Al₃ Er phase reaches to 1.5 at.% after annealing at 873 K.The temperature effect is not obvious for the phase equilibria at 673 and 873 K,but it increases the solubility of Er in β-Al₃ Y,while it is not obvious for both the solubility of Y in Al₃ Er and that of Er and Y in(Al).The phase equilibria of the Al-Er-Y ternary system determined by the present work have provided new phase diagram data for a future thermodynamic assessment of this system.     

Transport properties of structures containing a-Si : H : Er

The I–V characteristics of diode structures containing sputtered a-Si : H : Er films for potential LED applications have been studied. The a-Si : H : Er films were deposited on p⁺ Si substrates. On top of the film, ZnO : Al transparent conductive layers, 3 mm in diameter, were deposited. The back contacts were made of Al. The Er concentration in the films was varied between 0.05 and 0.16 at %, and the hydrogen concentration between 14 and 24 at %. It was found that the log–log plot of the forward I–V characteristic of a typical sample consisted of several regions with different slopes. On the basis of models put forward in the literature, it is proposed that the electron transport in the studied structure is governed by unipolar carrier injection, and the space charge limited currents are controled by two types of electron trap. The first are probably deep acceptor traps formed by dangling bonds, and the second are donor-like levels created by Er–O complexes. The energy positions of these traps are estimated.     

Plastic deformation of Fe–Al polycrystals strengthened with Zr-containing Laves phases: I. Microstructure of undeformed materials

The microstructures of several Fe-rich Fe–Al–Zr alloys have been studied as a basis of investigating the mechanical behaviour, which is subject of Part II. The alloys with only low Zr contents show microstructures with a relatively soft matrix and a hard skeleton along the grain boundaries, the latter being residual eutectics containing the matrix phase and the Zr(Fe,Al)₂ Laves phase. Scanning electron microscopy, orientation imaging microscopy as well as transmission electron microscopy and diffraction are used to study the grain sizes, the orientation relationships between the grains and the phases and the crystallography of the Laves phase. With higher Zr contents above about 10 at.%, the matrix is formed by the Zr(Fe,Al)₂ Laves phase.     

Microstructure characteristics of thick aluminum alloy plate joints welded by fiber laser

It's difficult to weld high strength thick plate since the groove is huge when using traditional arc welding, and the weld tends to be softened and large deformation could occur after multi-layer welding. All of these can affect the industrial application of high strength thick plate wielding. In this case, developing advanced welding technology and welding material is necessary to optimize the microstructure and performance of the welds. Fiber laser has many advantages such as good monochrome and high quality laser beam. In order to decrease the heat damage to the base metal from the welding heat source, low heat input is employed for welding thick plate. Fiber laser is applied in the welding of 20 mm thick Al–Zn–Mg–Cu alloy with super narrow gap filler wire. The microstructure comparison of Al–Mg–Mn alloy and Al–Mg–Mn–Zr–Er alloy welded joints reveals that a huge amount of fine equiaxed grains is formed in the weld zone of Zr and Er micro-alloying Al–Mg–Mn alloy welding wire and a great number of precipitation strengthening phases are precipitated in the weld zone after the heat treatment of welded joints in the entirety.