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Hardness Increases (hardness + increase)
Selected AbstractsLaserstrahlschweißen von Titanwerkstoffen unter Berücksichtigung des Einflusses des SauerstoffesMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 9 2004J. P. Bergmann titanium; colorations; laser welding; shielding device Abstract Im Rahmen dieses Aufsatzes wird erstmalig ein innovatives Konzept zum Laserstrahlschweißen von Titan für die Serienfertigung dargestellt und validiert. Durch den neuartigen Einsatz eines 6-lagigen Metallgewebes ist es möglich, die Strömung vom Schutzgas so stark zu beruhigen, dass die beim Schweißen schädlichen Verwirbelungen vermieden werden können. Der Einbau eines derartigen Gewebes als Boden einer offenen Schweißkammer ermöglicht sowohl das mechanisierte als auch das vollautomatisierte Schweißen von hochreaktiven Werkstoffen, wie zum Beispiel Titanwerkstoffen, unter atmosphärischen Druckbedingungen und unter inerter Abdeckung. Damit wird der für eine industrielle Fertigung, insbesondere für Industrieroboter, notwendige Freiheits- und Zugänglichkeitsgrad zur Fügestelle im Vergleich zu konventionellen geschlossenen WIG-Schweißhauben gewährleistet. Von weitgehender Bedeutung für die Schweißtechnik von Titanwerkstoffen ist es, dass auch die Bereiche, die in der Praxis mittels einer Nachschleppdüse vom Schutzgas nicht erreichbar wären, wie z.,B. die Überlappgebiete bei der Überlappnaht, erfolgreich durch das Prinzip der wirbelfreien Schweißkammer geschützt werden können. Mit Hilfe dieser neuartigen Vorgehensweise und eines modernen Fügeverfahrens, wie dem Nd:YAG-Laserschweißen, konnten erstmalig systematische Grundlagenuntersuchungen zum Einfluss von Sauerstoff in der Schweißumgebung auf die Mikrostruktur und auf die mechanisch-technologischen Eigenschaften einer Modellschweißverbindung durchgeführt werden. Durch die Validierung des gesamten Systems konnte bewiesen werden, dass im Vergleich zum konventionellen WIG-Verfahren geringere Anforderungen an die Reinheit des Schutzgases, um Anlauffarben und unzulässige Aufhärtungen zu vermeiden, gerichtet werden können. Für das Laserstrahlschweißen kann ein maximaler Restsauerstoffgehalt von 1000 ppm in der Schweißumgebung unbedenklich toleriert werden. Für das WIG-Schweißen gilt dagegen ein Höchstwert von etwa 30 ppm. Ferner konnte nachgewiesen werden, dass die Qualitätsmerkmale der derzeitigen Regelwerke für das WIG-Schweißen für die Luft- und Raumfahrttechnik auf das Verfahren Laserstrahlschweißen mit Nd:YAG-Quellen übertragen werden können. Influence of the oxygen content in the shielding gas on microstructure and mechanical properties of laser welds of titanium and titanium alloys In the present work, a new tool concept for laser welding of titanium in high volume production has been presented and evaluated. Through the innovative application of a six-layer metal web it is possible to calm the argon gas flow and avoid pernicious turbulences during welding. The integration of the mentioned metal web at the base of an open welding chamber allows the automated welding of highly reactive materials, such as titanium, under atmospheric pressure and inert shielding conditions. The higher density of argon relative to air offers the unique possibility to leave the chamber open on the top, so that a higher degree of flexibility than gas shielding devices for TIG welding, especially for industrial robots, is attained and can be successfully used for industrial mass production. Furthermore this device is important for welding three-dimensional contours or to shield the regions of overlap (in overlapped joints) where shielding gas trailers are unsuccessful. By means of the presented gas shielding procedure and a modern laser welding process such as Nd:YAG laser welding, systematic investigations on the effect of oxygen on the microstructure as well as on the mechanical properties of reference bead-on-plate weldments could be performed for the first time. As a result of these welding trials it can be concluded that in order to avoid discolorations and hardness increase, lower restrictions to the purity of the shielding gas, in comparison to TIG welding condition, can be allowed. The maximum tolerable value of oxygen in the welding atmosphere was found to be approximately 1000 ppm for laser welding. On the contrary the maximum value for TIG welding is about 30 ppm. Further investigations on the microstructural and mechanical properties of the joints confirm that the optical quality assurance criteria for TIG welding due to the standards of aircraft construction transferable to Nd:YAG welding are. [source] Bulk nanostructured titanium fabricated by hydrostatic extrusionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2010Krzysztof Topolski Abstract The paper is concerned with the use of Hydrostatic Extrusion (HE), which is one of the methods of Severe Plastic Deformation (SPD), for grain refinement of titanium grade 2. Titanium in the form of rods was subjected to multi-stage extrusion. The aim was to optimize the HE process so as to obtain nanostructured titanium rods. The results show that it is possible to produce nanostructured Ti rods of a diameter suitable for industrial applications. The refinement to nano-sized grains is accompanied by a significant improvement of mechanical properties. The tensile strength of more than 1000MPa was achieved and the hardness increase exceeded 50%. This study was also concerned with the problem of up-scaling the dimensions of nano-refined components produced by HE. The basic condition for HE to yield nanostructured Ti is that an appropriately high accumulated strain should be applied (, > 3). The results demonstrate that, by using HE, we can produce nano-Ti rods with diameters amounting to ,8mm. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanical Properties of Sputter-Deposited Titanium-Silicon-Carbon FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2001James E. Krzanowski The effect of SiC additions on the mechanical properties of TiC films was investigated. Ti-Si-C films with varying SiC content were deposited using dual-cathode radio-frequency magnetron sputtering. The nanoindentation hardness of these films increased with SiC content to a maximum of 20,22 GPa for films in the range of 15,30 at.% SiC. The elastic modulus was also measured, and the hardness to modulus ratio (H/E) increased with SiC content, indicating that hardness increases were due to microstructural effects. The residual stress was measured in several films, but was low in magnitude, indicating that hardness measurements were not influenced by residual stress. TEM examination of several films revealed that the SiC additions altered the film microstructure in a manner that could account for the observed hardness increases. [source] Development and high stress abrasive wear behavior of milled carbon fiber-reinforced epoxy gradient compositesPOLYMER COMPOSITES, Issue 7 2008Navin Chand Milled carbon fiber-reinforced polysulfide-modified epoxy gradient composites have been developed. Density and hardness increases with the increase of carbon fiber content in the direction of centrifugal force, which shows the formation of gradient structure in the composite. High stress abrasive wear test was conducted on the gradient composites by using a Suga Abrasion Wear Tester. Abrasive wear rate reduced on increase of milled carbon fiber content from 0.15 to 1.66 vol%. Reduction in abrasive wear rate in milled carbon fiber-reinforced epoxy gradient composites has been attributed to the increase of hardness, presence of random milled fibers, and debris of composite materials, which gave resistance and reduced wear rate. There is a small decrease in specific wear rate on adding 0.15 vol% milled carbon fibers. Further decrease of specific wear rate is observed on adding 0.45 vol% milled carbon fibers. After 3 N load, there is a decrease in specific wear rate behavior on adding 0.45 vol% carbon fibers, which further decreases on adding 0.60 vol% of carbon fibers. There is a remarkable decrease in specific wear rate up to 5 N load for 1.66 vol% milled carbon fiber-reinforced composite. Reduction in specific wear rate on adding milled carbon fibers is based on the formation of debris, which remained intact in their respective positions due to the interfacial adhesion between milled carbon fibers and epoxy resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] | ||||||||||