稀土及固溶处理对AM60B合金组织和力学性能的影响

研究了RE和固溶处理工艺对AM60B合金组织和力学性能的影响。结果表明，AM60B的抗拉强度随着RE的增加有显著提高，屈服强度、伸长率也有所提高。固溶热处理（T4）后，Mg17Al12相基本溶解，稀土化合物Al11RE3相未溶解但形貌略有改变，并且合金抗拉强度进一步提高与RE的加入量有关，当RE的含量达到1.6％时，其抗拉强度达到最高。RE的加入和热处理对合金的硬度基本无影响。     

稀土钇对Zn-25Al铸态组织及力学性能的影响

以Zn-25Al合金为基体材料,通过常规铸造方法制备了不同稀土含量的锌铝合金。采用金相显微镜、扫描电镜、拉伸试验机、硬度计等分析研究了稀土Y对试验合金显微组织和力学性能的影响。试验结果表明,添加稀土钇后,在锌铝合金中,其与Al、Zn等元素形成硬度高、热硬性好的复杂成分化合物且分散于晶界和枝晶中,细化了组织,有效地阻碍了高温时基体的变形和晶界移动。随着钇含量的增加,在室温、100℃和180℃3个温度下合金的抗拉强度和硬度基本上呈先升后降的趋势。当钇含量为0.6%时合金的综合性能最好,高温强度和硬度提高显著。180℃时的抗拉强度比不加Y时提高33.3%,硬度提高64.9%。当钇含量超过0.6%时力学性能下降。     

稀土合金对高铬铸铁共晶组织及性能的影响

高铬铸铁的韧度与枝晶间共晶碳化物的数量与分布有密切关系。通过定向凝固试样,考察了稀土合金对亚共晶及共晶成分高铬铸铁共晶组织的影响,测定了奥氏体（γ）一次臂的横截面积（Dγ）、共晶区域直径（EW）及碳化物间距（FSC：共晶区域中心碳化物间距;FSC：共晶区域边界碳化物间距）,以及力学性能。结果表明,稀土合金对高铬铸铁共晶组织有明显的细化作用,对其韧度也有一定的贡献。本文还对稀土的作用机理进行了讨论。     

稀土相对AZ61镁合金力学性能的影响

研究了以AZ61镁合金为基体,添加不同含量的La、Ce、Nd、Gd稀土元素,生成的第二相尤其是稀土相Al11La3、Al4Ce、Al2Nd、Al2Gd对AZ61镁合金力学性能的影响。AZ61+2%Gd合金中的第二相大部分呈球粒状,其有利于提高合金的综合力学性能。     

铈、镧及富铈混合稀土对AZ91D合金组织和力学性能的影响

用SEM、XRD和EDS分析了添加0.5%,1.0%,1.5%铈、镧和富铈稀土的AZ91D合金的微观组织形貌和相组成;并测试了各合金的硬度以及不同温度下的拉伸性能。结果表明:铈、镧和富铈稀土的添加均能细化AZ91D合金α相,降低β相含量,同时形成针杆状Al11RE3化合物。添加同一稀土元素的合金中,当稀土含量为1.0%时,其常温和高温抗拉强度达到最大值。对比相同含量不同元素的作用,低含量时含铈合金抗拉强度较好,高含量时含镧合金常温和高温断后伸长率较高;铈、富铈混合稀土、镧提高合金硬度的作用依次减弱。     

稀土、镍、锰对铝硅合金熔敷金属中铁相形态的影响

用氩弧将铁、镍、稀土、锰直接或间接熔入铝硅合金表面，研究这些元素对含铁量为1．03％—6．92％的焊缝中铁相形态的影响。研究发现，稀土含量低时可抑制针状铁相；稀土含量大于一定量就会生成针状的Al—Si—Fe—Ni—Fe相，该针状相的长度随稀土含量的增加而增加。铝硅合金中加入铁、锰、稀土后，熔敷金属中出现四辫状Al——Si—Mn—Fe相。若加入等量的Fe、Ni，熔敷金属中会形成间断的A1—Si—Fe—Ni状组织；若同时加入锰，除了生成网状结构外，还合同时存在四辫状Al—Si—Mn—Fe相和三辫状的Al—Si—Mn—Fe—Ni相。在铝硅合金中，单独加镍、同时加稀土和镍、同时加稀土和锰、同时加锰和镍均可很好地抑制针状铁相。锰、镍抑制针状铁相的效果明显优于稀土。     

稀土对铸造铝硅合金中氢的影响

研究了稀土对铝硅合金液态和固态含氢量的影响,找出了稀土最佳加入量的范围,探讨了稀土对铝硅类合金氢的存在状态及各状态下氢的含量的影响,以及稀土氢化物和Ｒｅ－Ａｌ－Ｓｉ多元金属间化合物的固氢作用。     

AlTiB和AlTiBRe对铝合金晶粒细化的影响

研究了AlTiB和AlTiBRe中间合金细化剂对铝合金的细化效果和细化机理，实验发现AlTiBRe对ZL104合金的细化效果优于AlTiB，两种细化剂对Al—1．4Mg合金均有细化作用，但细化效果的区别并不明显。金相实验结果表明，当稀土含量合适时，AlTiBRe中的Re不但在铝合金熔体中起良好的除杂作用，提高了铝合金的合金化程度，而且可以细化枝晶组织。     

Mg-4%Al-0.8%Sb-xRE镁合金的显微组织和力学性能

以锑元素取代Mg-4%Al-2%RE(AE42)镁合金中的部分稀土元素,制备了Mg-4%Al-0.8%Sb-xRE合金(x<2%),用SEM、XRD、万能拉伸试验机等分析了合金显微组织和力学性能随稀土元素含量x的变化.结果表明:铸态AE42镁合金的显微组织主要由α-Mg基体、针状及少量的颗粒状Al11RE3相组成;加入0.8%的锑元素后,随着合金中稀土元素含量的减少,基体中针状Al11RE3相的数量逐渐变少且形态逐渐变短、变细,同时基体中出现了弥散分布的小颗粒状RE2Sb和大颗粒状RESb化合物相和少量的骨骼状β-Mg17Al12相,且RESb相逐渐增多、变大;随着合金中稀土元素含量的增加,合金的力学性能逐渐提高,当稀土元素含量达到1.3%时,合金的力学性能基本达到AE42钱合金的水平.     

ZM5-0.1%RE阻燃镁合金表面氧化膜的结构及阻燃机理

为提高镁合金的起燃温度,在ZM5镁合金中添加了质量分数为0.1%的混合稀土(RE),对该合金表面进行了EDS、SEM和XRD分析.结果表明:在高温熔炼时合金表面生成了一层由RE2O3、MgO、Al2O3、Mg17Al12组成的厚度为2.5～3.μm的致密氧化膜;氧化膜最外表面没有稀土,而在基体和最外表面层之间混合稀土含量很高,质量分数为26.39%;稀土比镁更易氧化,致密的氧化膜抑制了基体镁合金的进一步氧化.     

硼含量对铅镁铝合金组织与力学性能的影响

采用真空熔炼法制备了含硼的铅镁铝合金,通过扫描电子显微镜、X射线衍射仪、能谱仪和力学性能试验机等研究了硼含量对合金组织与力学性能的影响。结果表明:添加硼后,合金中出现了黑色的颗粒状AlB2相,且与Mg-Mg17Al12共晶组织相伴生;随着硼含量的增加,AlB2相分布趋于均匀化,Mg-Mg17Al12共晶相增多;当硼的质量分数为1%时,合金的力学性能最好,抗拉强度、硬度和伸长率分别为105MPa,160MPa和6.87%,室温拉伸断口主要为韧性断裂和准解理断裂的混合特征。     

硼含量对Ni3Al合金抗氧化性能的影响

本文研究了硼含量对Ni3Al合金抗氧化性能的影响。结果表明,当硼含量在0.11～0.29wt%时,合金的抗氧化性能明显改善,而更高的硼含量由于生成了复杂的硼氧化物,破旧坏了Al2O3氧化硼的完整性,使合金的抗氧化性能恶化。     

Effects of electromagnetic stirring and rare earth compounds on the microstructure and mechanical properties of hypereutectic Al–Si alloys

In this paper, the effects of rare earth addition and electromagnetic stirring on the microstructure and the mechanical properties of hypereutectic Al–Si alloys have been reported. Hypereutectic Al–Si alloy was prepared using liquid metallurgy route and modified with the addition of cerium oxide. To control the structure, slurry of hypereutectic Al–Si alloy was subjected to electromagnetic stirring before pouring into the mould. It was observed that the addition of cerium oxide (0.2 wt.%) refined the primary silicon particles and modified the eutectic silicon particles. Further, the electromagnetic stirring of the hypereutectic Al–Si alloy reduced the average size of primary silicon particles, from 152?±?9 to 120?±?6 μm, and the length of β-intermetallic compounds decreased from 314?±?12 to 234?±?10 μm. Similarly, the application of electromagnetic stirring on cerium oxide-modified hypereutectic Al–Si alloy also reduced the average size of primary silicon particles from 98?±?5 to 76?±?4 μm and the average length of β-intermetallic compounds from 225?±?7 to 203?±?5 μm. Mechanical properties namely tensile strength, ductility and hardness of the alloys were improved with electromagnetic stirring and addition of cerium oxide appreciably.     

Wear and abrasion of cast Al-Alumina particle composites

Wear rates for cast aluminium and Al-Si alloys containing up to 5 wt.% γ-Al₂O₃ particles (100 μm size) were determined under conditions of adhesive wear and abrasive wear against a hardened steel disc and an alumina abrasive cloth sheet respectively. The adhesive wear rate of aluminium containing 5 wt.% A1₂O₃ dispersions is similar to that of Al-11.8Si eutectic alloy and slightly higher than that of A1-16Si hypereutectic alloy. Al-3wt. %Al₂O₃ and Al-5wt.%Al₂O₃ composites perform better than Al-11.8Si and Al-16Si hypereutectic alloys under abrasive wear conditions. Al-11.8Si and Al-16Si alloys have a lower abrasive wear resistance than pure aluminium. The results indicate that Al₂O₃ particles can be used as a substitute for silicon as the hard dispersed phase in aluminium for wear-resistant and abrasion-resistant applications.     

The influences of macrosegregation, intermetallic particles, and dendritic spacing on the electrochemical behavior of hypoeutectic Al-Cu alloys

The purpose of this research is (1) to investigate the influence of Al(2)Cu intermetallic particles associated with the dendritic arm spacing on the corrosion resistance of different hypoeutectic Al-Cu alloys and (2) to evaluate the electrochemical behavior of a hypoeutectic Al-Cu alloy directionally solidified under unsteady-state heat flow. The as-cast samples were produced using vacuum arc remelting and vertical upward water-cooled solidification. Microscopic examinations were carried out with optical microscopy and scanning electron microscopy + energy dispersiveX-ray analyses. To evaluate the surface corrosion behavior of such alloys, all corrosion tests were performed in a 0.5-M NaCl solution at 25 degrees C using an electrochemical impedance spectroscopy technique and potentiodynamic polarization curve analysis. Based on the tests, corrosion rate and impedance parameters were obtained. The present research has underlined the use of appropriate techniques of characterization for determining Al(2)Cu distribution, morphology, and fraction within the typical microstructures of Al-Cu alloys. The experimental results have established correlations between the Al-rich phase dendritic arm size, the intermetallic particles distribution in the eutectic mixture, the macrosegregation profile, and the resulting corrosion resistance.     

Electron crystallography applied to the structure determination of Nb(Cu,Al,X)2 Laves phases

The presence of primary precipitates of the Laves phases considerably improves the mechanical properties and the resistance to thermal degradation of the high‐temperature shape memory Cu–Al–Nb alloys. The structure analysis of the Laves phases was carried out on particles contained in the ternary and quaternary alloys as well on synthesized compounds related to the composition of the Nb(Cu,Al,X)₂ phase, where X = Ni, Co, Cr, Ti and Zr. The precise structure determination of the Laves phases was carried out by the electron crystallography method using the crisp software.     

长周期堆垛相对Mg-Zn-Y合金的阻尼性能影响

采用氩气保护条件下真空熔炼的方法熔炼出MgZnxY1.33x(x=1～4 at.％)合金,并运用SEM、XRD及阻尼测试方法对合金的组织结构和阻尼性能进行分析和讨论.结果表明,合金中主要包含镁基体和长周期堆垛相,随着Zn和Y含量的增加,合金中晶粒逐步细化,长周期堆垛相含量增多,并且针状或带状的长周期堆垛相互穿插在一起.阻尼测试的结果表明,长周期堆垛相的增加有利于镁合金的阻尼性能,Mg-7 ％Zn-12.8％Y合金在高应变阶段阻尼最优,其阻尼值达到0.04.     

Crystallographic Characteristic of Intermetallic Compounds in Al-Si-Mg Casting Alloys Using Electron Backscatter Diffraction

The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mechanical properties in Al-Si-Mg alloys. But intermetallic compounds in cast Al-Si-Mg alloy intermetallics are often misidentified in previous metallurgical studies. It was described as many different compounds, such as AlFeSi, Al8Fe2Si, Al5(Fe, Mn)3Si2 and so on. For the purpose of solving this problem, the intermetallic compounds in cast Al-Si alloys containing 0.5% Mg were investigated in this study. The iron-rich compounds in Al-Si-Mg casting alloys were characterized by optical microscope(OM), scanning electron microscope(SEM), energy dispersive X-ray spectrometer(EDS), electron backscatter diffraction(EBSD) and X-ray powder diffraction(XRD). The electron backscatter diffraction patterns were used to assess the crystallographic characteristics of intermetallic compounds. The compound which contains Fe/Mg-rich particles with coarse morphologies was Al8FeMg3Si6 in the alloy by using EBSD. The compound belongs to hexagonal system, space group P2m, with the lattice parameter a=0.662 nm, c=0.792 nm. The β-phase is indexed as tetragonal Al3FeSi2, space group I4/mcm, a=0.607 nm and c=0.950 nm. The XRD data indicate that Al8FeMg3Si6 and Al3FeSi2 are present in the microstructure of Al-7Si-Mg alloy, which confirms the identification result of EBSD. The present study identified the iron-rich compound in Al-Si-Mg alloy, which provides a reliable method to identify the intermetallic compounds in short time in Al-Si-Mg alloy. Study results are helpful for identification of complex compounds in alloys.     

Comparison of the machinability and wear properties of magnesium alloys

AZ and AS series magnesium alloys were used in this study and had different contents (i.e., 0 to 9 wt.% Al). The effect of zinc (Zn) and silicon (Si) on wear resistance and machinability was analyzed in AZ and AS series magnesium alloys. Zn amount in AZ series (1 %) and Si amount in AS series (1 %) were kept at a fixed rate. The effect of the changes in Al amount on hardness, wear resistance, and machinability in AZ and AS series magnesium alloys was comparatively analyzed. A higher increase was observed in the wear resistance of alloys in AS series magnesium alloys due to the rise in Al amount compared with AZ series. Intermetallic phases found in the microstructure of alloys (β-Mg₁₇Al₁₂ and Mg₂Si) were established to have an impact on the wear resistance and machinability of alloys.