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Fe‐based shape memory alloys are supposed to be an interesting and cost‐effective alternative to NiTi‐based alloys. In this work, the thermo‐mechanical behavior of a novel Fe–Mn–Si–Cr–Ni–VC shape memory alloy produced using standard air‐casting facilities is characterized as well as in the hot forged and cold rolled state. Besides a certain pseudoelasticity, the alloy shows good shape recovery properties and remarkably high shape memory stresses after heating to temperatures of only 160 °C, making the alloy interesting for commercial applications that make use of the shape memory effect.

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In order to improve the rolling contact fatigue (RCF) behavior of gear steels, a concept to increase their damage tolerance is developed alternatively to the conventional approach of improving the degree of steel cleanliness. For that purpose, Cu is used as a main alloying element in order to trigger the precipitation of nano‐sized Cu precipitates which shall improve the strain‐hardening rate of the martensitic matrix of Cu‐alloyed 18CrNiMo7‐6 steel surrounding a non‐metallic inclusion during plastic deformation. In this way, early component failure may be avoided and the maintenance costs of, e.g., wind energy converters may be kept low. The experimental analysis shows that nano‐sized Cu precipitates influence the material's strength, ductility, and strain‐hardening behavior under tension, depending on their coherence. Among others, the latter is related to strain‐induced martensitic transformation of coherent Cu. The structure of the Cu precipitates is studied by TEM and SANS analysis. The Cu‐alloyed steel also shows an increased hardening‐exponentCHT studied by cyclic hardness test (CHT) PHYBALCHT. Fatigue tests of specimens with coherent precipitates show cyclic hardening until a critical stress amplitude. Above that, stress amplitude cyclic softening is detected. An increased damage tolerance could be obtained for a 1 mass‐% Cu‐alloyed 18CrNiMo7‐6 steel.

The hydrodeoxygenation (HDO) of ethylene glycol over MgAl2O4 supported NiMo and CoMo catalysts with around 0.8 and 3 wt% Mo loading was studied in a continuous flow reactor setup operated at 27 bar H2 and 400 °C. A cofeed of H2S of typically 550 ppm was beneficial for both deoxygenation and hydrogenation and for enhancing catalyst stability. With 2.8-3.3 wt% Mo, a total carbon based gas yield of 80-100 % was obtained with an ethane yield of 36-50 % at up to 118 h on stream. No ethylene was detected. A moderate selectivity towards HDO was obtained, but cracking and HDO were generally catalyzed to the same extent by the active phase. Thus, the C2/C1 ratio of gaseous products was 1.1-1.5 for all prepared catalysts independent on Mo loading (0.8-3.3 wt%), but higher yields of C1-C3 gas products were obtained with higher loading catalysts. Similar activities were obtained from Ni and Co promoted catalysts. For the low loading catalysts (0.83-0.88 wt% Mo), a slightly higher hydrogenation activity was observed over NiMo compared to CoMo, giving a relatively higher yield of ethane compared to ethylene. Addition of 30 wt% water to the ethylene glycol feed did not result in significant deactivation. Instead, the main source of deactivation was carbon deposition, which was favored at limited hydrogenation activity and thus, was more severe for the low loading catalysts.

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KurzfassungKurzzeitverfahren zur Bewertung von Ermüdungseigenschaften metallischer Werkstoffe sind von großem wissenschaftlichem und wirtschaftlichem Interesse. Eine typische Fragestellung sind Wärmebehandlungsprozesse, bei denen eine große Variantenvielfalt auftritt und die Einflüsse individueller Prozessparameter zu bewerten sind. Mit PHYBALCHT, das auf einer zyklischen Härteprüfung beruht, wird am Lehrstuhl für Werkstoffkunde der TU Kaiserslautern ein solches Kurzzeitverfahren entwickelt. Mit PHYBALCHT kann der Proben- und Versuchsaufwand zur Ermittlung von Ermüdungseigenschaften metallischer Werkstoffe gegenüber konventionellen Verfahren erheblich reduziert werden. Aus Kraft-Eindringtiefen-Hysteresen wird eine plastische Eindringtiefenamplitude ha,p analog zur plastischen Dehnungsamplitude ermittelt und als Funktion der Zyklenzahl N aufgetragen. Dieser Messwertverlauf ist für jeden Werkstoff und Werkstoffzustand charakteristisch. Die mit PHYBALCHT ermittelten Kennwerte zeigen eine sehr gute Korrelation mit dem zyklischen Verfestigungsverhalten der untersuchten Stähle.

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