Structural states of aluminum-lithium alloy 1469 sheets

The texture and microstructure of the central layers in alloy 1469 sheets and the orientations of hardening T₁-phase precipitates are studied by X-ray diffraction, optical microscopy, and transmission electron microscopy. These studies and X-ray diffraction performed in asymmetric geometry demonstrate that the texture of the material is formed by the broadening of the orientations located near a β skeleton line. The contribution to an X-ray diffraction pattern from two of the four possible versions of the orientations of hardening T₁-phase plates that are caused by a brass-type texture component in the matrix and the orientation relationships between the matrix and the T₁-phase lattices is separated. The microstructure of the sheets is shown to have a two-level character. It is formed by extended (up to several millimeters long) regions fragmented into grains several microns in size. The structural states of the sheet material are discussed in their relation to the crystallographic character of fatigue crack propagation.     

Crystallographic texture and structure of rolled Al-Cu-Li alloy sheets

The crystallographic texture of billets—namely, forgings and a pressed strip made of an Al-Cu-Li alloy—and sheets rolled from them has been studied by X-ray diffraction. The results obtained are used to estimate the structural state of the rolled metal of the sheets fabricated according to various schemes. Pronounced crystallographic orientations {110}〈112〉 and {113}〈332〉 in the sheets rolled from the pressed strip correspond to a homogeneous fine-grained grain structure of the aluminum matrix. This structure provides good ductility (δ = 10%) and small δ anisotropy in the rolled metal. The absence of a symmetrical texture “motif” in the pole figures recorded from the sheets rolled from the forged billets is related to the inhomogeneity of their recrystallized structure. This structure decreases the ductility characteristics of the sheets rolled from the forged billets.     

Trace element effects on precipitation processes and mechanical properties in an Al-Cu-Li alloy

A study has been made of how impurities (Na and K) and trace additions of indium, magnesium, and silicon affect the microstructure and related mechanical properties of an Al-Cu-Li alloy. Transmission electron microscopy (TEM) was used to determine the size and distribution of particles in four alloys. Indium and magnesium are both seen to stimulate T ₁ precipitation. Indium also modifies ϑ″ morphology, and magnesium greatly increases the number density of ϑ″ precipitates. Strain localization was observed in underaged Al-Cu-Li-In tensile samples, consistent with observed changes in precipitate structure. No superposition of the effects of indium and magnesium was seen. High-resolution analytical microscopy was used to inspect precipitates for segregation of trace elements during early stages of aging, but no segregation was found within the detection limits of the system. Variations in heat treatment were made in order to study nucleation kinetics and trace element interactions with vacancies. Indium, with a binding energy less than that of lithium, was not seen to interact with quenched-in vacancies, while magnesium, with a binding energy greater than that of lithium, had a strong interaction. Yield anisotropies and fracture toughnesses were measured. Removal of trace impurities of sodium and potassium correlated with improved fracture properties. Magnesium was observed to increase anisotropy, especially in the T8 temper. A model was used to explain the anisotropy data in terms of texture and precipitate distribution.     

X-ray diffraction study of the structural evolution in a grade 1469 (Al-Cu-Li) alloy during the production of hot-rolled sheets

X-ray diffraction is used to study the structural changes in a grade 1469 (Al-Cu-Li) alloy with a high lithium content that occur during the production of hot-rolled sheets according to the ingot → pressed strip → hot-rolled sheet schedule. In the pressed strip, a multicomponent Bs {110}〈112〉, Cu {211}〈111〉, and S {123}〈111〉 texture forms, which is typical of articles pressed from such alloys, and an unusual intense single-component texture of the Ex₁ {011}〈111〉 type forms in the hot-rolled sheets. Its formation is stimulated by cross rolling of the sheets. The low strength characteristics of the hot-rolled sheets after heat treatment are related to an elevated heating temperature used for quenching and to the oriented precipitation of the lamellar particles of the hardening T ₁ phase.     

Liquid-phase sintering of high-density compacts from atomized aluminum alloy powders

Conclusions An Investigation has been carried out into the phenomenon of disintegration of aluminum alloy particles along their grain boundaries by a melt appearing during sintering in the splidus-liquidus temperature range, which is accompanied by the formation of metallic surfaces free from alumina. Recrystallization of the secondary grain particles through the liquid phase leads to the formation of structure in the sintered material and disruption of surface oxide films on its particles.Translated from Poroshkovaya Metallurgiya, No. 1(289), pp. 29–34, January, 1987.     

Effect of silver,magnesium, and zirconium additions on aging of a V1469 alloy (Al-Cu-Li system)

The structural states of 1469 alloy (Al-1.3Li-3.4Cu-0.66Mg-0.44Ag-0.1Zr) are studied. It is found that particles of the dominant strengthening phase precipitating in aging have a complex structure. The phase core is formed by heavy elements, probably, zirconium or silver. During aging, aluminum and lithium layers grow sequentially on the core with the formation of particles of the hexagonal T₁ phase with lattice parameters a = 0.49 and c = 0.932 nm in the middle portion. The precipitations of the θ″ and θ′ phases are not detected. The elastic stress fields induced by lamellar precipitates are shown to organize the spatial distribution of lamellae and cause a “chessboard” effect.     

Sputtering targets made of an Si-Ti-Co alloy

The effect of the cooling rate on the microstructure and the micromechanical properties of a resistance air-cast Si-23% Ti-10% Co alloy and on the residual stresses in magnetron sputtering targets made of it is studied. The choice of a proper temperature schedule of melting the alloy and the optimum cooling rate of the alloy melt are shown to result in a homogeneous fine-grained structure of the alloy, high strength characteristics of the targets, and a low level of residual thermal stresses in them.     

Effects of nickel on the sintering behavior of Fe-Ni compacts made from composite and elemental powders

Injection-molded Fe-Ni parts made from composite and elemental powders were prepared, and the effect of nickel on the sintering of iron compacts was investigated. Dilatometry analyses showed that the alpha-gamma phase transformation temperature of the Fe-Ni compact changed from a fixed 912 °C for pure iron to a temperature range between 700 °C and 912 °C where two phases coexisted. The microstructure indicated that nickel impeded surface diffusion and slowed down the neck growth rate of iron powder in the early sintering stage. The dual phase and the small neck size at low temperatures suppressed the exaggerated grain growth, which usually occurs on carbonyl iron powders at 912 °C. It was also observed that nickel impeded the grain growth of iron at high temperatures. Thus, by reducing the exaggerated grain growth during phase transformation, impeding the grain growth at high temperatures, and with high diffusion rates of iron in Ni-rich areas, enhanced densification was obtained for Fe-Ni systems, particularly for those systems made from composite powders. However, when coarse nickel powder was added, expansion was observed due to the presence of large pores around nickel powders. These pores were formed because of the particle rearrangement which was caused by the Kirkendall effect.     

The results of an experimental study of an anti-Opisthorchis preparation made from plant raw material

A device operating by the principle of local negative pressure has been developed and patented in Russia. Its trial in 122 patients with erectile insufficiency in combination with conservative treatment showed that positive effect may be reached in patients subjected to partial intracavernous restorative surgery of the penis with unsatisfactory outcome.     

Numerical analysis of the formability of an aluminum 2024 alloy sheet and its laminates with steel sheets

A criterion for ductile fracture is applied to the formability prediction of an aluminum 2024 alloy sheet and its laminated composite sheets. Axisymmetric deep-drawing processes of the 2024 sheet and the laminates clad by mild steel sheets are simulated by the finite-element method. From the calculated distributions and histories of stress and strain, the fracture initiation site and the forming limit are predicted by means of the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the fracture initiation in the 2024 sheet with no appearance of necking is successfully predicted by the present numerical approach. Furthermore, it is found that the formability of the 2024 sheet is improved by sandwiching it with the mild steel sheets.     

Structural and hydraulic characteristics of porous materials made of VT6 titanium alloy fibers

The structural and hydraulic characteristics (maximum, average, and hydraulic pore diameters, permeability, and sinuosity of the pore channels) have been studied in materials made of discrete VT6 alloy fibers obtained by rapid solidification of a melt. The materials have structural parameters that are similar to those in materials made from smooth cylindrical fibers or powders and are superior in regard to permeability.Institute of Material Sciences, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6, pp. 85–89, May–June, 1995.     

Biocompatibility of nitinol alloy as an implant material

The biocompatibility of nitinol alloy as a potential implant material was investigated through in vivo studies on beagles. A high-purity alloy was fabricated into prototype bone plates and implanted into the femurs of beagles. Commercial cobalt-chromium (Co-Cr) alloy bone plates served as reference controls, an additional control data were obtained from beagles subjected to "sham" operations. The bone plates were removed from the animals and examined after exposures of 3, 6, 12, and 17 months. There was no evidence of either localized or of general corrosion on the surfaces of the bone plates and screws. Gross clinical, radiological, and morphological observations of the tissue at the implantation sites during the autopsies uncovered no signs of adverse tissue reactions resulting from the implants. Histological analyses were performed on samples of muscle and bone adjacent to the implantation sites, and of tissues removed from such organs as the liver, spleen, brain, and kidneys. No significant differences were noted between samples taken from controls and those taken from dogs exposed to the implants. Neutron activation analyses were carried out on suitable samples. The analysis data suggest that there is no metallic contamination in the organs due to the implants; however, there does appear to be some chromium contamination from the Co-Cr alloy implants in the adjacent bone. On the basis of the totality of the data, it is concluded that nitinol alloy is sufficiently compatible with dog tissue to warrant further investigation of its potential as a biomaterial.     

The characteristics of the contact area of an endoprosthesis made from Ostek graphite-based material and of the mandibular bone fragment

Interactions between endoprostheses made of carbonic composition "Ostec" and bone tissue were studied after plastic repair of experimental vast defects in the mandible in 22 rabbits and 10 dogs over the course of 2 years. Histologic findings showed the formation of a layer of fibrous connective tissue 3 months after the operation and later; at some places the implant directly joins the rabbit bone, which frequently undergoes chondroid transformation. Microscopically, the structure of "Ostec" represents carbonic threads forming large bundles. By the 6th and 12th months of experiment connective tissue elements penetrate the fissures between the bundles and the perforation gaps of the endoprosthesis, forming bone-like and bone structures in them.     

微量Mg、Ag对Al—Cu—Li系合金组织和性能的影响

研究了以Al-1.0Li-4.0Cu合金为基础，加入微量元素镁或银的合金薄板材料在180℃下时效不同时间的显微组织特征和室温拉伸性能，实验结果表明；单独加入镁或单独加入银都使基础合金获得较大的强化效果，但镁的单独作用比银要大；Mg和Ag共同加入则产生最大的强化效应，这说明Mg和Ag之间有强烈的相互作用。     

电镀厂化验废液中银的再生利用

针对电镀厂化验室产生的含银废液的再生利用方法进行了研究，建立了从电镀厂化验废液中回收银，并直接制成分析纯硝酸银的工艺。该方法简单可行，对减少化验室废水对环境的污染，提高银二次资源的利用率，降低化验成本具有现实意义。该工艺可推广到硝酸银消耗量较大的其他化验室。