Surface analysis of nickel-chromium dental alloys

In this study, the surface compositions of four commercially available nickel-chromium alloys, Neptune, Rexalloy, Regalloy T, and Vera Bond, were compared and correlated to the alloys' corrosion behavior. The alloys were chosen to be representative of alloys with acceptable and unacceptable Cr levels, with and without Be additions. The results showed that the non-Be-containing alloys exhibited a homogeneous Cr-Mo oxide surface which resulted in more corrosion resistant alloys. The Be-containing alloys were shown to have non-uniform oxide surfaces. Areas on the surfaces of these alloys were low in Cr and O and enriched in Be. The oxide surfaces of these alloys were more easily disrupted and provided little resistance to accelerated corrosion processes. Thus, it was found that not only were the Cr and Mo content of the alloys important for corrosion resistance, but the composition of the surface oxide as well.     

铝锂合金材料研究应用现状与展望

铝锂合金是一类具有广阔应用前景的航空航天结构材料，已经历经90余年的发展历程.从铝锂合金的研发、生产和应用角度看，我国与国外仍存有不小差距.按成型方式铝锂合金可分为变形和铸造2大类, 目前研究较多和广泛应用的是变形铝锂合金.文中从析出相、热处理、腐蚀性和焊接性等方面介绍了变形铝锂合金的研究现状.同时从发展应用以及合金开发等方面, 总结了铸造铝锂合金的研究现状.结合当前国内外铝锂合金的研究现状对铝锂合金的未来发展做出了展望.      

TiAl基合金的组织演变

综述了TiAl基合金中几种常见的组织演变,着重论述了变形TiAl基合金在热处理过程中的晶粒长大及动力学、TiAl基合金在冷却时层状组织的形成和全层状TiAl基合金在高温时的非连续粗化这3种组织演变。     

钼-铼-镧合金微观组织及力学性能研究

通过固-液掺杂法在Mo-Re合金中加入稀土La₂O₃纳米颗粒制备得到Mo-Re-La合金, 将Mo-Re-La合金与Mo-Re合金、纯Mo的微观组织及力学性能进行对比研究, 得到如下结论: 在纯Mo中添加低含量Re元素(质量分数3.5%) 对Mo-Re合金有明显的细晶强化效果; 将La₂O₃纳米颗粒加入Mo-Re合金进一步细化和强化了Mo-Re-La合金。     

Corrosion fatigue of die-cast and extruded magnesium alloys

To study the fatigue life of die-cast and extruded AZ91D, AM50 and AZ31 magnesium alloys, corrosion fatigue tests were carried out using a rotating beam type fatigue machine. Corrosive environment (3.5% NaCl) significantly decreases fatigue life of alloys, especially for extruded alloys. The fatigue data at high stresses were analyzed using fitting equations. Extruded alloys show a higher sensitivity to the action of NaCl solution in comparison with die-cast alloys; however, their corrosion fatigue life is longer than that of die-cast alloys. Corrosion fatigue behavior of Mg alloys correlates with their mechanochemical behavior. The latter was studied by the polarization measurements of the dissolution rate of strained alloys. TEM observations confirmed that the maximums on the curves of Mg dissolution rate dependence on the strain in NaCl solution appeared at the work-hardening stages due to the creation and destruction of dislocation pile-ups.     

Strip Casting of High Performance Structural Alloys

There exists a great need for the development of high performance alloys due to increasing demands for energy conservation and environmental protection. Application of strip casting shows a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews our Center's activities in the development of high performance alloys by strip casting. Examples include (1) Al alloys, (2) wrought Mg alloys, and (3) bulk metallic glass (BMG) alloys.     

贮氢合金进展

对贮氢合金的工作原理及应用,贮氢合金的基本类型及开发历史和发展趋势进行了综合评述。MmNi5系稀土合金和Laves相合金的开发应用已较为成熟,但其贮氢密度不高,高容量型的钒固溶体型合金和镁基合金是贮氢合金发展的新趋势。目前主要通过添加合金元素、开发制备工艺,改进微观相组织结构并兼以适当的表面处理,以提高钒固溶体型合金和镁基合金常温常压下的吸放氢特性及活化性能。     

Creep and tensile properties of several oxide dispersion strengthened nickel base alloys

The room temperature and 1365 K tensile properties and 1365 K tensile creep properties at low strain rates were measured for several oxide dispersion strengthened (ODS) alloys. The alloys examined included ODS Ni, ODS Ni-20Cr and ODS Ni-16Cr-4J5Al. Metallography of creep tested, large grain size ODS alloys indicated that creep of these alloys is an inhomogeneous process. All alloys appear to possess a threshold stress for creep. It is believed that the threshold stress is associated with diffusional creep in the large grain size ODS alloys and normal dislocation motion in perfect single crystalline ODS alloys. Threshold stresses for large grain size ODS Ni-20Cr and Ni-16Cr-4J5A1 type alloys are dependent on the grain aspect ratio. Because of the deleterious effect of prior creep on room temperature mechanical properties of large grain size ODS alloys, it is speculated that the threshold stress may be the design-limiting creep strength property.     

钼合金粉末冶金研究进展

钼及其合金具有优异的高温力学性能,被广泛应用于冶金、机械、化工、航空和核工业等领域。粉末冶金是钼合金的主要制备方法。通过固溶强化、第二相强化、细晶强化等多种强化手段可以提高钼合金的力学性能,从而拓宽钼合金的应用范围。本文介绍了粉末冶金制备钼合金的研究进展,包括粉体制备方法、压制工艺及坯体烧结工艺等,讨论了钼合金的强韧化方法及其机理,并展望了粉末冶金法制备钼合金的发展方向,以期对钼合金的设计和制备提供一些思路。     

Bi对Ag-Sn合金粉末内氧化机制的影响

采用内氧化增重法对不同铋含量Ag-Sn-Bi合金粉末在不同温度恒温内氧化的分析结果表明，合金粉末内氧化增重量的平方与内氧化时间成正比，氧在合金中的扩散过程是内氧化的控制过程；随Bi含量增加，内氧化速度显著增大。采用电子探针和X射线衍射分析探讨了铋改变氧在Ag-Sn合金中的扩散机制的原因。     

A comparative study on mechanical properties of ultrafine-grained Al 6061 and Al 6063 alloys processed by cryorolling

The present work has been focused to investigate the mechanical behavior and microstructural characteristics of cryorolled Al 6063 and Al 6061 alloys. Hardness and tensile tests of the cryorolled Al alloys were carried out to understand its deformation behavior. SEM/EBSD was used to characterise the microstructures of cryorolled Al alloys and observed the formation of ultrafine-grained microstructures in the materials due to severe plastic strain induced during cryorolling. XRD was used to analyse the formation of different phases during cryorolling of the Al alloys. It is evident from the present study that UFG Al alloys exhibit higher hardness and strength when compared to the bulk Al alloys due to the grain size, higher dislocation density and precipitation hardening effect. The cryorolled Al 6061 alloys exhibit higher tensile strength (346 MPa) and hardness (120 H_v) as compared to Al 6063 alloys (Tensile strength: 240MPa and Hardness: 96.5 H_v) in the present investigation. The deformation mechanisms of UFG Al alloys contributing to their enhanced strength are discussed.     

Si-Al合金电子封装材料性能及显微组织研究

采用热压烧结法制备了70%Si-Al和90%Si-Al两种合金,测量了两种合金的典型热性能和力学性能,并观察和对比了两种合金的显微组织。结果表明:随着Si含量从70%升高到90%,在各测量温度下,合金材料的线膨胀系数都降低。热压烧结制备的材料Si相细小,致密度高,界面结合力好,热导率高。随着Si相含量的增加,热压的Si-Al合金热导率逐渐降低。烧结的Si-Al合金的抗弯强度和弹性模量随Si相含量的增加逐渐降低,材料的断裂主要以Si相的脆性断裂为主。     

抗蠕变耐热镁合金的发展现状

讨论了镁舍金抗高温蠕变机理和提高镁合金抗高温蠕变的途径,重点介绍了Mg-Al系、Mg-Zn系和Mg-RE系耐热铸造镁合金的研究现状;对高性能耐热镁合金的发展趋势提出了一些见解,认为应该进一步优化合金元素,以解决铸造镁舍金在耐高温、抗蠕变等方面存在的问题。     

铝、镁、钛合金材料在汽车工业中的应用和发展

阐述了现代汽车为节能、环保而开始大量采用铝、镁、钛舍金材料；介绍了铝、镁、钛舍金材料的性质特点，采用铝、镁、钛合金材料制造的汽车部件；并指出铝、镁、钛材料在汽车工业中的应用和发展前景。     

AB5型贮氢合金结构分析

贮氢合金的电极性能取决于贮氢合金的微结构。从晶体结构、电子结构及化学键结构等各方面对市场上广泛应用的AB5型贮氢合金的结构进行综述，同时讨论合金结构与合金吸放氢性能之间的关系。     

钛合金的腐蚀机理及耐蚀钛合金的发展现状

钛及钛合金作为耐蚀结构材料在腐蚀工程中的应用已越来越广泛。综述了钛合金在不同腐蚀介质中的几种腐蚀行为及其腐蚀机理,概述了不同合金化元素的添加对钛合金耐蚀性能的影响及其作用机理,最后介绍了耐蚀钛合金的发展现状,以及今后耐蚀钛合金研究的发展方向。     

The large strain deformation of some aluminum alloys

The stress-strain behavior of both non-heat-treatable and heat-treatable aluminum alloys has been examined over a large strain range by a variety of deformation modes. In superpurity aluminum deformed in torsion, the work hardening rate approaches zero at strains of four to five, while a definite saturation in the flow stress is observed at much lower strains in the precipitation hardened alloys. In the non-heat-treatable alloys, a saturation in the flow stress is not approached at even very large strains. Nevertheless, the stress-strain behavior of all the alloys can be reasonably represented by a saturation type stress-strain equation. The deformation behavior of the alloys can be qualitatively understood in terms of the dislocation accumulation processes and slip morphology in the different alloys. Finally, it is shown that alloys deformed on a commercial rolling mill exhibit equivalent stress-strain behavior to that found in these laboratory deformation studies.     

Effects of hydrogen on mechanical properties of vanadium-niobium alloys

Mechanical properties of V-Nb alloys were investigated from 78 to about 300 K. The effects of alloying composition on the yield and flow stress are consistent with a hardening model due to the “misfit”" of one element in the matrix of the other. Additions of up to about 0.6 at. pct of hydrogen have a moderate strengthening effect on the yield stress of high vanadium alloys, but relatively little effect on the high niobium alloys. Little or no effect of adding hydrogen to any of the alloys was observed for the strain hardening coefficient. High Nb alloys were found to be much less embrittled by small additions of hydrogen than were high V alloys. In addition, the failure of severely embrittled alloys was found to be initiated intergranularly by impingement of mechanical twins on grain boundaries. It is speculated that the grain boundaries may be enriched hydrogen.     

铁基阻尼合金的研究现状及发展趋势

铁基阻尼合金具有良好的阻尼性能、力学性能和加工性能,在船舶减振降噪中可发挥重要作用。对铁磁类、层错类、复相类铁基阻尼合金的阻尼性能和力学性能进行了介绍,分析了3类铁基阻尼合金的阻尼机理,并对铁基阻尼合金的发展趋势,尤其在舰船方向的应用进行了展望。     

Investigation of the processes of obtaining plastic treatment and electrochemical behaviour of lead alloys in their capacity as anodes during the electroextraction of zinc I. Behaviour of Pb---Ag, Pb---Ca and PB---Ag---Ca alloys

The influence of the mode of obtaining and plastic treatment of binary Pb---Ag and Pb---Ca, and ternary Pb---Ag---Ca alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied.It has been established that the rolled Pb---Ag alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary alloys with calcium content of 0.06% causes Pb₃Ca precipitation in the solid solution. The hot-rolled alloys form an solid solution of Pb₃Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled alloys possess clearly expressed oriented structures also through the rolling direction.Cast and plastically deformed Pb---Ca anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than Pb---Ag alloys. Both Pb---Ca systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary Pb---Ag---Ca alloys. These alloys (Pb---Ag 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary Pb---Ca ones. Only ternary rolled alloys have equal corrosion and electrochemical properties to those of the alloy Pb---Ag (0.75%–1.0%) used in practice.