变形工艺对冷拔精密管性能的影响

介绍了有关冷拔精密管机械性能的工艺试验,阐述了影响冷拔精密管机械性能的因素和控制措施。     

超细WC—10Co硬质合金的显微结构与机械性能

本文对超细WC-10wt％Co-X硬质合金的机械性能进行了研究：通过喷雾干燥，用舍AMT和硝酸钴溶液来制取超细原始粉末，再用机械一化学工艺，将原始粉末还原和碳化成WC／Co粉末：直径大约为100nm的WC粉末与粘结剂Co均匀地混合，在n-已烷和球料比为5：1的条件下湿磨24小时，过后再干燥24小时，并在Imtorr压力下和1375℃二的温度下进行烧结：为了比较超细硬质合金的显微结构与机械性能，将直径为0．57μm～4μm的WC粉末与Co粉末进行混合，随后在1mtorr压力下和1375℃二的温度下烧结：添加不同数量的TaC、Cr3C2、和VC晶粒长大抑制剂到WC-10wt％Co超细硬质合金中，发现烧结后超细硬质合金中的Co相在WC晶粒的边缘快速产生：Hall-Petch类型关系说明WC—10wt％Co硬质合金的硬度是随着WC晶粒度的下降而增加，而抗弯强度则取决于Co粘结相中的溶解度。     

Dissolution mechanism of solid nickel in liquid zinc saturated with Fe

The dissolution behavior of solid nickel in static liquid zinc saturated with Fe at 723 K was studied. The results show that when immersing solid Ni in liquid Zn saturated with Fe, the intermetallic compound layers consisted of γ and δ phases are formed on nickel substrate, which is the same as that in liquid pure zinc. However, some F2 particles are formed in the liquid near the solid/liquid interface. These Г2 particles can easily heterogeneously nucleate on （particles and grow fast. The dissolution process is governed by diffusion of nickel atom across a concentration boundary layer in liquid Zn saturated with Fe, and is different from a mixed control mechanism of nickel in liquid pure zinc. The participation of Г2 particles makes the dissolution of solid Ni in the liquid accelerated.     

Friction stir welding of AZ31 magnesium alloy

Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.     

Cell-structure and mechanical properties of closed-cell aluminum foam

1　INTRODUCTIONMetalfoamsexhibitunusualmechanical,ther mal,acoustic ,damping ,electricalandchemicalprop ertiesthatcannotbefoundinsolidmaterials .Thosespecialpropertiesmayleadtoavarietyofapplicationsinstructuralandfunctionalproducts.Closed cellalu minumfoamisalight massstructuralmaterialofgreatpromise .Itsdensityisonlyafractionofthatofthecorrespondingbulkmetal,butitsstrengthissuf ficientlyhightobeusedintheautomobileindustry ,buildingindustryandtransportation .Examplesoftheirapplicationsinc…     

Evolution of Ti （C, N）-based cermet microstructures

Two series of Ti(C, N)-based cermet materials originating from the same chemical composition but with dif-ferent grain size distribution and sintered to different stages of the sintering cycle have been studied using SEM, TEM,EDX, and XRD. Much of the surrounding structure is formed during solid state sintering. During the solid state sintering, at first, the Mo and W rich (Ti, Mo, W)C inner rim is formed by the interaction among TiC, WC, and Mo2C; then the Mo and W lean (Ti, Mo, W)(C, N)outer rim is formed. During the liquid phase sintering, the outer rim of coarse grains grows rapidly throw a solution-reprecipitation process; aLso coarse grains grow by particle coalescence. The interface between coarse grain outer rim and binder is flat (crystal surface).     

Aging properties and microstructures of Ti-B20 titanium alloy

A new metastable beta titanium alloy of Ti-Al-Mo-V-Cr-Fe-Zr-Sn system was designed and named Ti-B20. In order to investigate the aging properties and microstructures of the new alloy .subjected to different solution treatments, the tensile and Vickers hardness tests were carried out and the optical microscope and scanning electron microscope analysis were performed. The results show that the new alloy displays rapid aging response, high age strengthening effect and fine deposition. In addition, beta solution results in ultra high age hardening effect with low tensile ductility, whereas excellent combination of aging strength and ductility can be obtained after solution treated below beta transus temperature.     

Si复合Al2O3-SiC材料热机械性能的研究

通过应力-应变关系、高温抗折强度等高温试验，研究了金属硅复合Al2O3-SiC材料的热机械性能，结合SEM和XRD，对金属硅复合Al2O3-SiC材料高温显微结构和物相进行分析。结果表明：金属硅作为一个组元，不仅能缓解Al2O3-SiC材料由于热膨胀系数不匹配产生的内应力，而且使Al2O3-SiC材料兼具有金属塑性的特点，从而改善了Al2O3-SiC无机材料热机械性能。     

一种β型Nb-Ti基合金的显微结构和机械性能

近年来 ,体心立方Nb -Ti固溶合金已成为中等温度结构件的候选材料。因为这些合金具有良好的综合性能 ,即高强度 (室温强度约 10 0 0MPa～ 12 0 0MPa)、高持久强度(70 4℃时强度仅下降约 3 5 % )、中等断裂韧性 (约 3 5MPam )和疲劳裂纹生长抗力。合金研究表明 ,一种多元体心立方固溶强化的Nb -3 5Ti -6Al -5Cr -8V -1W -0 5Mo -0 3Hf -0 5C合金在空气中于10 0 0℃以下是体心Nb -Ti基合金中强度最高的。但早期研究表明 ,多元合金具有VanGoghSky (VGS)型显微结构。所谓VGS结构表示形貌上与VanGoghSky油画相似 ,是铸造过程中显…     

时效对接触线用Cu-Ag-Cr合金性能的影响

分析了固溶温度、时效及时效前冷变形量对Cu - 0 1 %Ag - 0 1 %Cr接触线用合金性能的影响 ,结果表明 :经 870℃固溶、 40 %～ 5 0 %冷变形及 480℃× 1 5h时效处理后 ,合金可获得良好的综合性能。