合金元素对Zr基大块非晶晶化行为的影响

利用准晶的共轭结构模型构造出了Zr基非晶合金中准晶相的原子结构模型,用递归方法研究了合金元素对非晶晶化过程的影响.结果表明:Zr基非晶合金析出的准晶相存在Zr6Ni,Ni6Zr2种结构,Ni6Zr结构优先析出;合金元素Ag,Pd,Pt,Au固溶于准晶中时,占据Cu,Ni原子的位置,增大近邻原子间的相互作用,这从电子理论角度解释了合金元素Ag,Pd,Pt,Au稳定地促进二十面体准晶(I)相析出的事实.     

Effect of Minor Alloying Elements on the Oxidation Behavior of Ni-Base Alloys in a High-Temperature Steam Environment

Oxidation of Metals - Model alloys based on Alloy 617 were fabricated with modified minor alloying elements for improvement in oxidation resistance in high-temperature steam environments. Model...     

The Effect of Alloying Elements on the Microstructure of Al-5Fe Alloys

The effects of adding Cr, Mn, and Zr on the microstructure of Al-5Fe alloys has been studied by metallographic analysis, scanning electron microscopy, x-ray diffraction analysis, and differential thermal analysis. It has been found that the effects of the different elements on the microstructure of ferro-aluminum intermetallics in Al-5Fe alloys are not alike. Addition of Cr in Al-5Fe alloys dissolves only into AlFe intermetallics, resulting in the morphology of the AlFe phases being changed with increasing Cr content. Cr is a favorable nucleating agent for encouraging metastable Al _x Fe (x = 4.6 to 5.0) phase formation. Adding Mn in Al-5Fe alloys may stabilize the metastable Al₆Fe phase, helping the primary phase field of Al₇Cr diminish or even disappear and forcing Cr to dissolve into AlFe phases. Adding Zr does not refine the primary AlFe intermetallics. Al₃Zr particles in Al-5Fe alloys will occupy the growing spaces of ferro-aluminum phases and indirectly hinder the growth of Fe-bearing phases.     

等离子喷涂热障涂层的高温氧化行为研究

采用等离子喷涂工艺在K38高温合金基体上分别制备了Y2O3稳定的ZrO2(YSZ)和MgO稳定的ZrO2热障涂层(MSZ),利用热重分析、X-射线衍射和带能谱的扫描电镜等手段,研究分析了两种涂层在900℃和1000℃的高温氧化性能.结果表明:YSZ涂层和MSZ涂层在900℃都有较好的抗高温氧化性能:MSZ涂层在1000℃氧化时发生了相变,引起陶瓷外层开裂,影响了涂层的抗氧化性能和使用寿命,而YSZ涂层在1000℃氧化没有相变发生,表现出比MSZ涂层更佳的抗氧化性能.     

合金元素对镁合金耐热性能的优化作用及机理

论述了耐热镁合金的研究现状.介绍了锂、硅、钙、锡、铋、锑、银、钍、稀土以及其中的钕、锆元素对镁合金性能尤其是耐热性能的作用及影响机理,总结了提高镁合金高温性能的途径.最后指出发展耐热镁合金的主要方向.     

Oxidation Behavior of ODS Fe–Cr Alloys

Four experimental oxide dispersion strengthened (ODS)Fe-(13–14 at. %)Cr ferritic alloys were exposed for up to 10,000 hr at 700–1100 °C in air and in air with 10vol.% water vapor. Their performance has been compared to other commercial ODS and stainless steel alloys. At 700–800°C, the reaction rates in air were very low for all of the ODS Fe–Cr alloys compared to stainless steels. At 900°C, a Y₂O₃ dispersion showed a distinct benefit in improving oxidation resistance compared to an Al₂O₃ dispersion or no addition in the stainless steels. However, for the Fe-13 %Cr alloy, breakaway oxidation occurred after 7,000 hr at 900°C in air. Exposures in 10 % water vapor at 800 and 900°C and in air at 1000 and 1100°C showed increased attack for this class of alloys. Because of the relatively low Cr reservoirs in these alloys, their maximum operating temperature in air will be below 900°C.     

稀土元素对Nb-Si基超高温合金的合金化作用和抗氧化涂层改性作用

由铌基固溶体和金属间化合物组成的Nb-Si基超高温合金是当前新型高温结构材料的研究热点,但是其抗氧性能较差制约了合金的应用,合金化和涂层制备是提高抗氧性能的重要途径,稀土在合金化和涂层改性两个方面都具有特定的益处。综述了在合金化时添加稀土(Y、Ce、Dy、Ho)对微观组织和力学性能的影响,论述了稀土或稀土氧化物(Y、Ce、Y_2O_3、CeO_2)对硅化物抗氧化涂层的改性作用机理。     

主要合金元素对镁合金组织和性能的影响

本文叙述了一些常用镁合金以及新近发展起来的某些新型镁合金的成分、组织及性能;重点介绍了合金元素对这些镁合金组织和性能的影响。     

合金元素对Mg—Zn—Gd合金组织和力学性能的影响

采用金相显微分析、X射线衍射、扫描电子显微镜和室温拉伸试验,研究了合金元素Zn、Gd对Mg-Zn-Gd合金铸态组织和力学性能的影响.结果表明,当Zn含量不变时,随着Gd含量的增加,合金中的第二相依次从准晶相(I相) Mg7Zn3相、I相到I相 W相转变,二次枝晶臂间距明显减小,晶粒细化,晶间组织也由颗粒状、细线状向封闭的网状转变;当保持x(Zn)/x(Gd)=5.8不变时,合金第二相的组成不变,枝晶相分布更加细密,第二相也随之增多.拉伸测试表明,当Zn含量不变时,随着Gd含量的增加,合金的抗拉强度和伸长率均增加,但屈服强度先升高后降低;同比例增加Zn、Gd的含量,合金的强度升高,伸长率降低.     

合金元素对Mg-Er-Zn-Zr合金铸态组织和力学性能的影响

研究了合金元素Zn和Zr对Mg-Er-Zn-Zr合金铸态组织和力学性能的影响。结果表明,(Mg_(97.5)Er_2Zn_(0.5))_(99.82)Zr_(0.18)、Mg_(97)Er_2Zn_1和(Mg_(97)Er_2Zn_1)_(99.82)Zr_(0.18)合金都呈现典型的树枝晶结构。由于Zn元素的增加,(Mg_(97)Er_2Zn_1)_(99.82)Zr_(0.18)比(Mg_(97.5)Er_2Zn_(0.5))_(99.82)Zr_(0.18)的组织明显细化,二次枝晶臂的间距减小,第二相由非连续网状分布变成了片层状分布。Zr元素的添加使得合金晶粒细化,第二相呈现更加弥散分布,第二相组成没有发生变化,依然由X-Mg_(12)Er_1Zn_1相和(Mg,Zn)x Er相组成。随着Zn元素和Zr元素含量的增加,合金的力学性能明显提高。     

Effect of Ternary Elements on the Oxidation Behavior of Aluminized TiAl Alloys

The effects of ternary elements added to TiAl on the coating layer formed by the pack-aluminizing process was studied with respect to oxidation resistance and mechanical properties. All the TiAl specimens, with various amounts of Nb, Cr, Fe, and V, were pack aluminized under identical conditions using a high-activity process. Among the ternary alloying elements tested, Nb showed the best property of the TiAl₃ coating layer formed on the surface and, consequently, the best oxidation resistance. The TiAl₃ coating layer becomes thicker and has a finer grain size as the content of Nb or Cr is increased. Microhardness tests revealed that the addition of Nb or Cr improved the toughness of the coating layer and thus improved the cracking resistance. Cyclic oxidation tests showed that the TiAl₃ coating layer formed on the TiAl alloy has better oxidation resistance with increasing Nb content. The ductility and oxidation resistance of the TiAl₃ coating layers improved with Nb addition, which contributes to the grain refinement of TiAl₃. The Nb present in the TiAl₃ coating layer inhibits grain growth by the solute-drag effect and retards inward diffusion of Al to the TiAl matrix by forming (Nb, Ti)Al₃ precipitates during high-temperature oxidation.     

合金元素在Mg－Li基合金中的作用

概述了合金元素在Ｍｇ－Ｌｉ基合金中的作用的研究现状、存在问题、解决途径及发展趋势。     

等离子喷涂YSZ热障涂层的热腐蚀行为研究

为了研究YSZ热障涂层在热腐蚀环境下的服役情况,采用等离子喷涂工艺在K38高温合金基体上分别制备了Y2O3稳定的ZrO3（YSZ）热障涂层和MgO稳定的ZrO2热障涂层（MSZ）,利用热重分析、X-射线衍射和带能谱的扫描电镜等手段,研究分析了这2种涂层在850℃含氯硫酸盐膜下的热腐蚀行为。结果表明：MSZ涂层在850℃热腐蚀时发生了相变,引起陶瓷外层开裂和剥落,影响了涂层的抗高温性能和使用寿命;而YSZ涂层在850℃腐蚀后没有相变发生,表现出了比MSZ涂层更佳的抗热腐蚀性能。     

典型β型钛合金元素Cu，Fe和Cr的偏析规律

通过对Ti-2．5Cu，Ti-3Fe，Ti-3Cr，Ti-13Cu-1Al，Ti-6Al-1．7Fe几种合金铸锭成分的对比研究，建立了典型β钛合金元素的偏析模式。对Ti-2．5Cu，Ti-3Fe，Ti-3Cr合金铸锭的对比可知，Cu和Fe元素的偏析程度大，Cr元素的偏析程度小；对Ti-2．5Cu和Ti-13Cu-1Al合金铸锭的对比可知，Cu元素在2种合金铸锭中的偏析均比较明显，Cu含量越高，偏析程度越大；Cu元素在2种合金铸锭的晶界有截然不同的偏析方式，Cu元素在Ti-13Cu-1Al的晶界富集而在Ti-2．5Cu的晶界贫化。对Ti-3Fe和Ti-6Al-1．7Fe合金铸锭的对比可知，Fe元素在2种合金铸锭中的偏析均比较明显，Fe含量越高，偏析程度越严重；Fe元素在2种合金铸锭的晶界均贫化。     

Effects of Surface Chemistry on Splat Formation During Plasma Spraying

Ni-Cr single splats were plasma-sprayed at room temperature onto aluminum and stainless steel substrates, which were modified by thermal and hydrothermal treatments to control the oxide surface chemistry. The proportions of the different splat types were found to vary as a function of substrate pretreatment, especially when the pretreatment involved heating. It was observed that surface roughness did not correlate with changes in splat morphology. Substrate surfaces were characterized by X-ray photoelectron spectroscopy using in situ heating in vacuum to determine the effect of thermal pretreatment on substrate surface chemistry. It was found that the surface layers were composed primarily of oxyhydroxides. When the substrates were heated to 350 °C, water vapor was released from the dehydration of oxyhydroxide. Preheating the substrate can remove the water prior to spraying: preheated substrates had improved the physical contact between the splat and substrate, which enhanced the formation of disk splats and increased the number of splats.     

合金化元素对Nb-Si基超高温合金微观组织和性能的影响

Ti、B、Al和Cr等元素对Nb-Si基合金组织和性能影响的研究和报道较多,而对Zr、Mo、W和Hf等元素的研究报道较少,这些元素的加入不仅能够优化Nb-Si基合金的微观组织,也能使合金的综合性能明显提升。系统的分析和归纳这些合金元素的加入对Nb-Si基合金组织和性能的影响,对今后Nb-Si基超高温合金的设计和应用有着重大的意义。本文重点关注了Zr、Mo、W和Hf等合金元素对Nb-Si基合金组织、力学性能和高温抗氧化性能的影响。     

Effects of Silicon on the Oxidation Behavior of Ni-Base Chromia-Forming Alloys

This paper compares and analyzes the oxidation behavior of Ni-base alloys with and without about 2.7 wt.% Si addition. The Ni-base alloys studied were of two types: cast model alloys or wrought commercial alloys. Oxidation testing was conducted at 1000°C in still air. The specific aspects studied were scale spallation resistance, nature by which the silicon oxidized, and the influence of silicon on the subsurface depletion behavior of chromium. From oxidation results of the cast model alloys, Si addition was found to improve oxidation resistance by forming a continuous SiO₂ layer at the alloy/scale interface, which resulted in decreased oxidation kinetics. The cast alloys with Si addition also showed larger average effective interdiffusion coefficients of chromium compared to the cast alloys without Si addition. As a consequence, the Si addition assisted in the establishment and re-formation of a chromia scale during oxidation. In the case of the wrought commercial alloys, a discontinuous distribution of SiO₂ precipitates in the vicinity of the alloy/scale interface was found to be beneficial to cyclic oxidation resistance.     

合金元素对Mg-Li合金组织及性能的影响

合金化可以细化Mg-Li合金晶粒,从而提高综合力学性能,还可以改善合金耐蚀性、热稳定性。本文综述了Al、Zn、碱土元素和稀土元素等常用元素对Mg-Li超轻合金微观组织和性能的影响,一般情况下,Al和Zn主要通过固溶强化提高Mg-Li合金强度,碱土元素主要通过细晶强化来提高Mg-Li合金强度,稀土元素则通过细晶强化和金属间化合物的第二相强化来提高Mg-Li合金的综合性能。本文还指出了Mg-Li超轻合金合金化存在的问题及发展趋势。