Yield loci of Zircaloy tubing with different textures

Abstract

Yield loci of four batches of Zircaloy-4 canning tubes with different textures were measured at room temperature for quadrants I and IV (axial tensile or compressive stresses in combination with internal pressure). The circumferential and axial strains were continuously recorded using applied strain gauges and maximum plastic strains of about 0.2%.

A comparison with the yield loci determined by Knoop hardness measurements gave marked differences in the shape of the yield loci. The experimental results showed that the shape of the yield loci of Zircaloy tubing can be altered by texture variations, mainly by changes in the tilt angle of the basal poles of the hexagonal zirconium crystals from the radial towards the tangential direction of the tubes. The yield loci of tubes with a sharp ideal orientation can be calculated successfully for all four quadrants on the basis of the active slip or twinning systems for specific biaxial loading conditions. It is shown that the use of the Von Mises yield criterion is limited to only a few texture and stress conditions.

Résumé

Les points d'ecoulement de quatre lots de tubes en Zircaloy-4, ayant des textures différentes, ont été mesurés à l'ambiante pour les quadrants I et IV (contraintes axiales de tension ou de pression juxtaposées a une pression interne). Les déformations circonférentielles et axiales furent continuellement enregistrées à l'aide de jauges de déformation et de déformations plastiques d'environ 0.2%.

Des différences marquées dans la forme du point d'écoulement furent observées en comparaison avec celle mesurée par dureté Knoop. Les résultats expérimentaux ont montré que la forme du point d'ecoulement de tubes de Zircaloy peut être modifiée par des variations de texture surtout par des changements dans l'angle d'inclinaison des pôles du plan de base du zirconium, de la direction radiale vers la direction tangentielle des tubes. On peut ca1culer avec succés le point d'écoulement pour les quatre quadrants, de tubes ayant une orientation idéale marquée, en se basant sur les systèmes actifs de glissement ou de maclage pour des conditions spécifiques de contrainte biaxiale. On montre qu'on peut utiliser le critère d'écoulement de von Misès seulement pour quelques conditions de texture et de contraintes.     

Influence of filament orientation and fabrication variables on the properties of fiber-reinforced metals

Continuous tungsten-filament, reinforced silver-matrix composites were prepared by electroplating, cold pressing, and hot pressing techniques followed by sintering, in the range of 2 to 33 vol pet filaments. Orientation of the filaments with respect to the tensile axis was varied between 0 (parallel) and 90 deg. The properties determined were the ultimate tensile strength, 0.1 pct yield strength, proportional limit, elongation, and elastic modulus. The results indicate that the strength essentially followed the rule of mixtures. A misalignment exceeding 10 to 15 deg drastically reduces strength. A small misalignment of less than 10 deg not only does not lower the strength but greatly improves the ductility. Five different fracture paths were identified as a function of fiber orientation. Both ductile and brittle fracture were observed in the tungsten filaments. Many of the features of deformation and fracture were characterized by Scanning Electron Microscopy.     

Effect of oxygen on the mechanical properties of copper and copper-matrix composites hardened by melt-synthesized chromium carbides

Thermal analysis is used to study the saturation of the copper melt by oxygen from an oxygen-containing gas phase and the possibility of deoxidation of this melt by nanosized diamond–graphite, which enters in the reaction mixture used to synthesize chromium carbide in the production of copper-matrix composites, are studied. The oxygen and chromium carbide contents are found to affect the mechanical properties of copper and copper-matrix composites. Diamond–graphite is shown to have a high refining ability, which can substantially increase the plasticity of copper and copper-matrix composites. A low chromium carbide content is found to play a modifying role in grain refinement, and a high chromium carbide content is shown to cause the formation of a precipitation-hardened structure and an increase in the physicomechanical properties of copper-matrix composites.     

氧含量对TC4 ELI钛合金棒材组织及力学性能的影响

采用自主制备的两种氧含量的TC4合金铸锭,通过开坯-锻造-退火等工艺制备出间隙元素含量远远低于GB/T 13810-2017及UNS R56401要求,性能优异的TC4 ELI钛合金棒材.通过化学分析、金相显微镜、拉伸试验和扫描电镜研究其性能,结果表明,经过开坯-锻造-退火,钛合金棒材氧氮氢等间隙元素含量较铸锭有较明显...     

低氧MHC合金板材的制备及力学性能

采用粉末冶金方法和热轧工艺制备了低氧MHC合金轧制板材,通过化学分析、金相分析、硬度测试、拉伸力学性能测试研究了低氧MHC合金的显微组织和力学性能。研究表明：通过调节C/Hf原子比、钼粉还原并结合真空烧结等手段,可以有效降低合金中的氧含量。不同温度下退火后样品显微组织分析和力学性能测试结果对比表明,合金板材在1 300℃以下为回复阶段,随着退火温度的增加,1 300℃开始发生再结晶,强度和硬度逐渐下降,塑性提高,在1 600℃时再结晶完成,完全再结晶的低氧MHC合金板材塑性优异。     

Effects of oxygen and heat treatment on the mechanical properties of alpha and beta titanium alloys

Two alloys, Ti-6Al-2V and Ti-2Al-16V, simulating the alpha and beta phases of Ti-6A1-4V, respectively, were prepared with oxygen concentrations from 0.07 to 0.65 wt pct (0.20 to 1.83 at. pct). Their microstructure, deformation behavior, and strength were investigated with X-ray diffraction, microscopy, and mechanical tests to determine the effects of oxygen concentration and heat treatment. In both alloys the hardness increases in identical fashion with the square root of oxygen concentration. The alloys' strengths also depend on heat treatment, but in different ways. Whereas the alpha alloy is non-age-hardenable, the beta alloy's strength can be doubled by aging. The hardening effect of oxygen is generally unaffected by heat treatment, except for the alloys with the highest oxygen concentrations. During aging of the alpha a small amount of Ti₃Al can form, and slight age-hardening occurs. The ductility of the alpha alloy is little affected by aging. On the other hand, oxygen causes a change from good ductility at low oxygen concentration (0.07 wt pct) to total brittleness at 0.65 wt pct oxygen, independent of heat treatment. In the beta alloy there are complex phase transformations depending on heat treatment. Its deformation behavior varies from very ductile in solutiontreated and quenched (STQ) condition to totally brittle in aged conditions. The aging embrittlement appears to be caused by alpha and some omega precipitation. Decoration of the beta grain boundaries with precipitates accounts for the intergranular brittle fracture. Oxygen, on the other hand, is not an embrittler, although it reduces the ductility of the beta alloy.     

Effect of bainite on the mechanical properties of dual-phase steels

The bainite-martensite-ferrite steels (tri-phase steels) were made in the laboratory by intercritical annealing, bainite transformation and oil quenching in sequence. With bainite inclusions, ductility was improved substantially without significant reduction of tensile strength. The ductility increase was found to be due to large deformation after necking and increased work-hardening.     

Effect of copper additions on the mechanical properties of iron

The effect of copper alloying on the mechanical properties of iron is studied. Alloying of a model material (armco-iron) with 0.2–2.0% Cu is shown to increase the strength characteristics by a factor of 1.5–2.5 and to decrease the ductility by 8–60%.     

Effect of cathodic charging on the mechanical properties of aluminum

The effects of cathodically charged hydrogen on the mechanical properties of pure aluminum have been studied through the use of tensile and microhardness tests. The effects have been further examined with TEM observations of the microstructural changes that accompanied the charging. Hydrogen charging was found to reduce the ductility and increase the yield and tensile stresses in tensile tests. Microhardness tests revealed that cathodic charging produced a severely hardened surface region. The hardness in this region quickly saturated, and further charging increased the depth of this region. TEM observations in this hardened layer revealed an increased dislocation density commensurate with the hydrogen charging. It was also found that the recovery of the hardened layer takes place in two stages: the first around 100 °C and the second around 350 °C. J. W. WATSON, Formerly Graduate Student, Department of Materials Science and Engineering, Northwestern University, Evanston, IL Y. Z. SHEN, Deceased, was a Visiting Scholar, Department of Materials Science and Engineering, Northwestern University, from Shanghai Internal Combustion Engine Research Institute, Shanghai, People’s Republic of China     

Effect of hydrogen on the mechanical properties of iron-base superalloys

In this study the effect of Ti, Al, Ni, and Mn variations on the strengths of eight laboratory scale heats of an iron-base superalloy (Fe + 15 pct Cr + 25 pct Ni + Ti + Al) was investigated. The aging response at 873 K, after either a 1173 or 1323 K solution treatment temperature, was monitored to determine which alloys (with respective heat treatment) had the highest yield strengths. Those having yield strengths of 700 to 1055 MPa and ductilities of 22 to 56 pct (RA) were thermally charged in hydrogen and tested in air, 69 MPa hydrogen and 69 MPa helium. After charging, the yield strengths were unchanged, but RA losses ranged from 40 to 90 pct. Microstructural observations are consistent with hydrogen transport by dislocations and trapping at the matrix-precipitate interface where the hexagonal Ni₃Ti(ώ) is the precipitate.     

Effect of prestrain on the mechanical properties of eutectoid steel

This investigation was designed to study the effect of prior compressive deformation and temperature on the subsequent dynamic fracture toughness, K,_Id, of fully pearlitic 1080 rail steel. Charpy instrumented impact tests on precracked specimens were performed at room temperature at a variety of prior strain levels from 0 to 20 pct. In addition, transition temperature tests were performed on specimens of zero, low (5 to 10 pct), and high (15 to 20 pct) prior strains. Dynamic fracture toughness (K,_Id) and energy absorbed per fractured area (W/A) were obtained from instrumented impact data. It was found that, at room temperature, compressive strain had no effect on either K_Id or W/A. In the transition temperature range, W/A decreased with increasing prior strain, while there was no effect on K_Id. At temperatures in the upper shelf region, prior strain decreased both K,_Id and W/A. There was no effect on the transition temperature as the amount of prior strain was increased. Thus, while both dynamic fracture toughness and impact properties can be significantly changed by varying temperature, cold working the material has at best a modest effect on impact energy and then primarily only in the upper shelf region.     

粉末氧含量对热等静压FGH4169合金力学性能与组织的影响

以氧含量分别为60×10~(-6),145×10~(-6)和216×10~(-6)的GH4169预合金粉末为原料,采用粉末热等静压法制备成块体合金,然后进行热处理,研究粉末氧含量对FGH4169合金的室温和高温力学性能及组织的影响。结果表明,随原始粉末氧含量从60×10~(-6)增加到216×10~(-6),Al和Ti元素在粉末表面富集,并生成斑点状氧化物;粉末氧含量对FGH4169合金的致密度无明显影响,但可改变合金中碳化物的分布和形态。高氧含量的FGH4169合金中易形成原始颗粒边界(prior particle boundary,PPB),PPB中含有碳化物和氧化物。FGH4169合金在室温和高温下的塑性均随氧含量增加而降低,粉末氧含量为60×10~(-6)和145×10~(-6)时,FGH4169合金在室温和650℃下的强度和塑性都能达到变形GH4169合金的标准值。     

Effect of cryorolling on the structure and the mechanical properties of ultrafine-grained nickel

Grain-boundary misorientations and mechanical properties of ultrafine-grained (UFG) nickel produced by equal-channel angular pressing are investigated after rolling at a temperature of ?196°C. It is shown that cryogenic rolling increases the fraction of high-angle grain boundaries almost two times in UFG nickel. The approach based on electron backscatter diffraction analysis is proposed to estimate the relative energy of high-angle boundaries in polycrystalline metals.     

热处理对TRIP 590钢微观组织及力学性能的影响

采用Gleeble3800热模拟机对TRIP钢拉伸试样进行不同工艺条件的快速热处理模拟实验,并采用金相分析、显微硬度测试等方法对试样进行组织观察和性能测试,目的是通过适宜的热处理工艺促使材料微观组织中出现适量的残余奥氏体组织,增强该材料在变形过程的相变诱导塑性(TRIP)效应,强化材料结果表明:在两相区内,TRIP钢中的残余奥氏体含量随着退火温度和退火时间的增加而增大,以25℃/s缓慢加热到700℃,再以150℃/s的速率快速加热到820℃保温120s后淬火处理,处理后的试样,残余奥氏体体积分数达到13％,显微硬度最高,达到262HV.     

The effect of processing variables on the mechanical properties and strain ageing of high-strength low-alloy V and V-N steels

Abstract

Laboratory experiments have been conducted on a series of vanadium and vanadium-nitrogen steels. The results indicate that the combination of vanadium plus nitrogen gives an excellent notch toughness in the normalized plates (EA TT < ?80°C). Controlled rolling gives about 100 MPa higher yield strength with somewhat reduced notch toughness (EATT? ?50°C). Aluminum does not improve the properties of a normalized or controlled-rolled vanadium-nitrogen plate. Vanadium is able to combine with nitrogen so effectively that the steel can be considered. to be unsusceptible to strain ageing.

Résumé

Les auteurs ont fait des essais de laboratoire sur une série d'aciers au vanadium et au vanadium-azote. Les résultats indiquent que la combinaison vanadium-azote donne d'excellentes propriétés de résilience pour des tôles fortes normalisées (EA TT < ?80 °C). Le laminage contrôlé conduit à une limite d'élasticité plus élevée d'environ 100 MPa et a une résilience quelque peu réduite (EATT ? -50°C). L'aluminium n'améliore pas les propriétés d'une tôle forte d'acier au vanadium-azote après normalisation ou après laminage contrôlé. L'efficacit;amp;#x00E9; de la réaction entre Ie vanadium et l'azote est telle que l'acier peut être consideéré comme n'étant pas susceptible au vieillissement après écrouissage.     

Effect of doping on the mechanical properties of nonlinear GaSe crystals

The effect of doping with sulfur, indium, tellurium, aluminum, erbium, and silver on the mechanical properties of nonlinear GaSe crystals grown by a modified Bridgman method with the rotation of a thermal field is studied. GaSe:S crystals have the best optical properties and GaSe:Al crystals have the highest microhardness. Under identical experimental conditions, we revealed an additive influence of double doping on the properties of GaSe: the crystals doped with sulfur and aluminum demonstrate the maximum efficiency of laser radiation frequency conversion and the maximum hardness. The increased hardness is supported by the appearing ability of the crystals to undergo cracking under the action of high-intensity radiation, which is characteristic of glass.     

Effect of molybdenum additives on the mechanical properties of iron-copper pseudoalloys

The effect of molybdenum additives (10%) on mechanical properties and the microstructure of iron-copper (Fe-30% Cu) pseudoalloys is investigated. The tensile strength, hardness, and electrical resistivity are determined, and the microstructure of specimens is analyzed quantitatively. It is established that during both solid-and liquid-phase sintering, no solid-phase solutions are formed, and a stable heterophase microstructure develops as the components undergo mutual diffusion. The heterophase nature of structure hinders grain growth of the refractory phase. The grain size of the sintered specimens does not exceed 1–5 µm. The plasticity of Fe-30% Cu-10% Mo pseudoalloys obtained during solid-phase sintering is increased significantly as compared with Fe-Cu alloys, and the elongation is 13.8% at a porosity of about 1%. Specimens produced by liquid-phase sintering experience greater elongation, but during prolonged liquid-phase sintering (more than 10 min), grain growth is restored, and the plasticity of the Fe-Cu-Mo specimens is reduced.