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Wenngleich der Verwendung von Mg-Knetlegierungen im Automobilbau ein großes Potenzial zugesprochen wird, ist deren Einsatz bislang von geringer Bedeutung geblieben. Im Rahmen des vom BMBF-geförderten Verbundforschungsvorhabens "MIA-Magnesium im Automobilbau" wurden daher in Zusammenarbeit der Firmen DaimlerChrysler AG, ThyssenKrupp Umformtechnik GmbH, Otto Fuchs Metallwerke KG, Honsel GmbH & Co. KG, GP Innovation GmbH, OSK Kiefer GmbH sowie der BTU Cottbus die Grundlagen für die prototypische Fertigung von Bauteilen aus den Mg-Knetlegierungen des Typs AZ31 und AZ 80 erarbeitet.
Influence of Mechanical Surface Treatments on the HCF Performance of the Ni-Superalloy Udimet 720 LI
(2003)
In the cast condition g titanium aluminide alloys that solidify completely through the b phase are
characterized by fine and homogeneous microstructures, weak textures and low segregation. For these reasons such alloys have a relatively good workability and can be closed-die forged without preceding ingot breakdown even if the alloys contain no large fractions of the b phase at the working temperature. The present work was devoted to a combined study of the constitution and microstructural morphologies that develop in various two-step heat treatments of a single-step forged b solidifying alloy. The
study included high-energy X-ray diffraction for in situ investigations of the constitution at the heat treatment temperature. It was observed that the phase ransformations are quite sluggish in the material which results in fine microstructures and some conditions that significantly deviate from thermodynamic equilibrium. Further, tensile and creep testing was carried out on the different material conditions in order to identify the range in which the properties can be varied. It is found that this easily forgeable material exhibits comparable strength, ductility and creep strength as more conventional peritectically solidifying alloys.
Tensile and high cycle fatigue (HCF) properties of the hot-rolled Mg-12Gd-3Y (wt.%) magnesium alloyhave been investigated. The magnesium alloy exhibits a fatigue strength of about 150 MPa, which ismuch higher than that of the commercial Mg-8Al-Zn alloy AZ80. Aging heat-treatment (T5) improvedthe fatigue life of the Mg-12Gd-3Y alloy. Fatigue cracks nucleated at the intense slip bands in theas-rolled alloy. After T5 treatment, however, the fatigue crack nucleation site shifted to the phase boundariesbetween MgGdY particles and Mg matrix. T5 heat-treatment retarded the crack initiation and thusimproved the fatigue life of the Mg-12Gd-3Y alloy.