Mitigation of heat treatment distortion of AA 7075 aluminum alloy by deep cryogenic processing using the Navy C-ring test

Heat treatment is a promising approach to advance the mechanical properties of AA 7075 aluminum alloy for aerospace structural applications. Quenching is commonly performed after solutionizing of AA 7075 aluminum alloy to impart supersaturated solid solution condition. It involves rapid cooling of the previously solutionized part to room temperature with water as a quenching medium. It leads to severe distortion of the structural part and deteriorates its surface integrity due to the high thermal residual stresses. This paper reports the distortion behavior of heat-treated AA 7075 aluminum alloy by implementing the standard Navy C-ring test. For precise measurements, the coordinate measuring machine (CMM) was used. Deep cryogenic treatment (DCT) was executed after conventional heat treatment (CHT) to reduce the tensile residual stresses and mitigate the distortion potential of AA 7075 aluminum alloy. Results showed significant improvement in surface finish and hardness of deep cryogenically treated AA 7075 aluminum alloy. It is attributed to the precipitation of fine spherical second phase particles distributed uniformly in the matrix. The distortion potential of heat-treated AA 7075 aluminum alloy is minimized by 30.7 % by deep cryogenic processing. It is correlated to the counterbalancing of tensile residual stresses in the heat treated part by compressive residual stresses ensued by deep cryogenic quenching.

Evaluation of the Performance of Cryogenically Treated Carbide İnserts in the Turning of AISI 1040 Steel

-In this study, the effects of cryogenic treatment on tool wear and surface roughness of tungsten carbide inserts coated with TiAlN were investigated as a function of cutting speed and feed rate. It is observed that the surface roughness increases with increased cutting speed, feed rate and also applied cryogenic processing. In other words, the effect of feed rate and cutting speed is very high on the surface roughness. On the other hand, the results showed that the cryogenic treatment is a non-effective process to enhance the wear resistance and tool life of inserts due to brittle region between coated layer and surface

An Overview on Recent Patents and Technologies on Solid Dispersion

The oral bioavailability enhancement of poorly water-soluble medicaments is still one of the most complicated aspects of the formulation development. Various approaches are currently available for solubility and rate of dissolution enhancement such as salt formation, solubilization and reduction of particle size, each with its own limitations and advantages. Solid dispersion is one of the most suitable approaches for the formulation development of poorly water-soluble drugs. The popularity of solid dispersion is evident from the increasing number of patent applications and patents granted in this field during recent years. This article reviews the various approaches for the preparation of solid dispersion such as a solvent melting, hot-melt extrusion method, solvent evaporation method, cryogenic processing approaches etc. from the perspective of patents filed or granted for these techniques. Some of the aspects taken into account before the preparation of solid dispersions are carrier selection and physicchemical testing along with an insight into the molecular arrangement of medicaments in solid dispersion. The manuscript further highlights various commercial patented technology platforms such as Solumertm, Hovione and Kinetisol which are based on the concept of solid dispersions.

Cryostructuring of Polymeric Systems. 52. Properties, Microstructure and an Example of a Potential Biomedical Use of the Wide-Pore Alginate Cryostructurates

Wide-pore cryostructurates were prepared via freezing sodium alginate aqueous solutions with subsequent ice sublimation from the frozen samples, followed by their incubation in the ethanol solutions of calcium chloride or sulfuric acid, rinsing, and final drying. Such sequence of operations resulted in the calcium alginate or alginic acid sponges, respectively. The swelling degree of the walls of macropores in such matrices decreased with increasing polymer concentration in the initial solution. The dependence of the degree of swelling on the cryogenic processing temperature had a bell-like character with a maximum for the samples formed at −20 °C. According to 1H NMR spectroscopy, the content of mobile (non-frozen) water in the frozen water-sodium alginate systems also depended on the initial polymer concentration and freezing temperature. The cryostructurates obtained did not lose their integrity in water, saline, in an acidic medium at pH 2 for at least three weeks. Under alkaline conditions at pH 12 the first signs of dissolution of the Ca-alginate sponge arose only after a week of incubation. Microbiological testing of the model depot form of the antibiotics entrapped in the Ca-alginate cryostructurate demonstrated the efficiency of this system as the antibacterial material.

AA2219 Aluminum Alloy Processed via Multi-Axial Forging in Cryogenic and Ambient Environments

This paper presents the microstructure and the mechanical behavior of nanocrystalline AA2219 processed by multi axial forging (MAF) at ambient and cryogenic temperatures. The X-ray diffraction pattern and transmission electron microscopy micrographs in the initial microstructure characterization indicate a more effective severe plastic deformation during the cryogenic MAF than the same process conducted at room temperature. MAF at cryogenic temperature results in crystallite size reduction to nanoscales as well as second phase particles breakage to finer particles which are the crucial factors to increasing the mechanical properties of the material. Fractography analysis and tensile tests results show that cryogenic forging does not only increase the mechanical strength and toughness of the alloys significantly, but also improves the ductility of the material in comparison with the conventional forging. In this comparative regard, cryogenic processing provides 44% increase in the tensile strength of the material only after 2 forging cycles when compared to the room temperature process. In addition, further forging process to the next cycles slightly enhances the tensile strength at the expense of ductility due to less ability of the dislocations to accumulate. However, the ductility of the ambient temperature forged samples decreases at a faster rate than that of cryoforged samples.

PEG-based cross-linked films with aligned channels: combining cryogenic processing and photopolymerization for the design of micro-patterned oriented platforms

Liquid flow along single channels occurs on micro-patterned polymeric platforms prepared by directional freezing and photopolymerization.