Ca对原位自生Mg2Si/ZM5复合材料组织与性能的影响

通过真空感应炉中氩气保护,在ZM5熔体中加入Si获得原位反应自生Mg2Si/ZM5复合材料.采用金相显微镜、环境扫描电镜、拉伸实验等研究了Ca对该材料组织与性能的影响规律.结果表明:Ca的加入改变了Mg2Si/ZM5复合材料中Mg2Si相的形貌,使其从不规则的汉字状变成较细小的多角形,从而改善了材料的力学性能;当加入0.05?(质量分数)时,复合材料的室温力学性能最好,屈服强度提高了10.4%,延伸率提高了52.4%;在200℃高温下,当含Ca0.05%～0.10%(质量分数)时其屈服强度和延伸率最好,分别提高了30.1%和92.3%.     

镁合金与钛合金的瞬间液相扩散焊

为实现镁合金AZ31B与钛合金Ti6A14V的可靠连接，研究了两者以Al为中间层的瞬间液相扩散焊接头的微观结构与连接强度。研究结果表明：当焊接时间为180min时，焊接温度是影响界面反应热力学与动力学的主要参数，其对接头的微观组织、接头界面新生相构成与连接强度有重要影响。保温温度低于450℃时，AZ3IB／AI界面无液相产生，无法实现AZ31B与Ti6A14V的可靠连接；保温温度在450℃～480℃变化时，温度对AZ31B／Al／Ti6A14V界面反应的动力学因素有明显影响，且直接决定了焊后接头新生相的构成与分布。470℃保温180min的接头剪切强度较高（72．4MPa），达到AZ31B母材（86MPa）的84．2％。     

镁合金焊接接头的力学性能

随着镬合金应用的日益广泛，其焊接接头的力学性能也受到人们的重视。介绍和分析了采用不同焊接方法时焊接接头的力学性能。并提出一些看法，对镬合金焊接接头力学性能的研究有一定促进作用。     

快速凝固Mg94.6Zn4.8Y0.6镁合金薄带的组织与性能

采用单辊快速凝固技术制备了Mg94.6Zn4.8Y0.6合金薄带,研究了薄带的组织及性能特征。结果表明:Mg94.6Zn4.8Y0.6镁合金快速凝固薄带组织由过饱和的单相-αMg固溶体组成,沿厚度方向分为两个晶区:近辊面粗大等轴晶区和自由面细小等轴晶区。Mg94.6Zn4.8Y0.6合金快速凝固薄带的显微硬度为85.95HV,在250℃左右保温2 h的显微硬度最高,超过该温度(250~300℃)显微硬度显著下降。     

Effect of temperature on mechanical behavior of AZ31 magnesium alloy

Strain rate sensitivity and tension/compression asymmetry of AZ31 magnesium alloy at different temperatures and strainrates were investigated.Both of mechanical behaviors are temperature dependent.Strain rate sensitivity increases with increasingtemperature.Thermally activated slip is the source of strain rate sensitivity.At the temperature below or near 373 K,strain ratesensitivity is very little.Tension/compression asymmetry in yielding decreases with increasing temperature.Twinning is the reasonof tension/compression asymmetry.At the temperature above or near 573 K,the material shows little tension/compressionasymmetry of the flow stress.     

Thermodynamic database of the phase diagrams in the Mg-Al-Zn-Y-Ce system

The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams （CALPHAD） method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.     

Wear resistance of ceramic coating on AZ91 magnesium alloy by micro-arc oxidation

The ceramic coating formed on AZ91 magnesium alloy by micro-arc oxidation （MAO） was characterized. The results show that the ceramic coating （3.4-23 μm in thickness）on the surface ofAZ91 alloy was attained under different micro-arc oxidation treatment conditions, which consist mainly of MgO, Mg2SiO4 and MgSiO3 phases. Nano-hardness in a cross-sectional specimen was determined by nano-indentation experiment. The MAO coatings exhibit higher hardness than the substrate. Dry sliding wear tests for the MAO coatings and AZ91 alloy were also carded out using an oscillating friction and wear tester in a ball-on-disc contact configuration. The wear resistance of the MAO coatings is improved respectively under different treatment time as a result of different structures of ceramic coatings formed on AZ91 alloy.     

定向凝固AZ31镁合金晶粒取向及力学性能研究

采用自行设计的定向凝固装置制备了AZ31镁合金铸件,通过金相观察、XRD分析和室温压缩试验,研究定向凝固工艺对AZ31镁合金晶粒取向和常温力学性能的影响。结果表明:定向凝固制备的AZ31镁合金铸件具有柱状晶组织,第二相呈球状弥散分布于晶粒内部。由于温度梯度的影响,晶体规律性地定向生长,呈现较明显的[1010]择优取向。该铸件在常温力学性能和塑性成形性能上表现出各向异性的特点。     

有机酯水玻璃砂在特大型铸钢件上的应用

以有机酯水玻璃砂替代CO2水玻璃砂,应用于特大型铸钢件的生产中。介绍了有机酯水玻璃砂的硬化机理。选用福建平潭20/40目原砂、模数为2.0~2.3的改性水玻璃、12%~16%的有机酯进行有机酯水玻璃砂配比。给出了混砂和造型操作过程中的注意事项。通过对油压机横梁、汽轮机缸体、油轮挂舵臂和宽厚板轧机机架等一些特大型铸钢件的生产,实践表明:采用有机酯水玻璃砂后,铸件质量明显提高,铸件气孔、裂纹减少,表面光洁,尺寸精度提高。     

活性酯硬化水玻璃砂的研究

用焙烧活性砂混制而成的活性酯硬化水玻璃砂与普通酯硬化水玻璃砂相比，强度成倍提高，从而减少水玻璃的加入量，改善水玻璃砂的溃散性。实验证明：原砂的表面活性直接影响在水玻璃砂中水玻璃的加入量，是改善水玻璃砂溃散性的关键之一。焙烧活性砂的水玻璃加入量只要１．５％～２．０％，即能满足实际生产的强度要求。