The Role of the Dislocation Nucleation Around Precipitates in the Mechanical Properties of a Fe-C Alloy

The effect of the dislocation nucleation around the precipitates on the mechanical properties of a Fe-0.02 wt%C alloy has been investigated by tensile testing and by means of transmission electron microscopy, and an attempt has been made to correlate tensile data with the observed dislocation configuration. After ageing for 30 min at 400℃, dislocation loops or helical dislocations were seen around many precipitates. These loops seemed to be produced by the prismatic punching from the precipitate-matrix interface, because the mean atomic volume of the precipitate is larger than that of the matrix. When the ageing temperature decreased to 150℃, dislocation loopes were seen only around some precipitates, and herical dislocations were rarely detected. The variation of the yield drop which is deformed at room temperature with ageing temperature has a minimum at 400℃ after ageing for 30 min. It has been suggested that the yield drop is associated with the dislocation nucleation around the precipitates when ageing or straining. In deformation at liquid nitrogen the specimens either fractured before yielding or necked immediately after yielding and the specimens containing large precipitates were less ductile than those with small precipitates. The stress concentration due to dislocations nucleated around the precipitates during straining will cause a cleavage crack of a precipitate particle and this cracking will initate cleavage microcracks in the adjacent matrix

Concept model of atomic hydrogen dry developing process for photolithographic patterning

Atomic hydrogen dry etching was used for microstructure fabrication. Photolithography was proposed and achieved by a dry development process using atomic hydrogen irradiation. The reaction system of poly(methyl methacrylate) mixed with molecular benzophenone was examined as a model system for a proof-of-concept study. Optical patterning was experimentally made on a thin layer of poly(methyl methacrylate) with benzophenone by UV light exposure with a photomask. The reaction system acted as a negative tone resist in the proposed process. Thus, a model system for a new atomic hydrogen dry development process was proposed and successfully demonstrated.Yuki Takemori, Masao Gohdo, Yuta Koda, and Hideo Horibe, "Concept model of atomic hydrogen dry developing process for photolithographic patterning", AIP Advances 10, 105223 (2020) https://doi.org/10.1063/5.0027509

Low Temperature Ultrasonic Attenuation in Magnesium and Magnesium Alloys

The ultrasonic attenuation in pure Mg and Mg-Li and Mg-N alloys was studied in the temperature range from 4.2°K to 300°K. In Mg, four peaks were observed in the attenuation vs temperature curves. The peaks were named as P_1, P_2, P_3 and P_4 from the low temperature side. P_1 was observed at about 20°K and the origin of which was confirmed to be the interaction between sound waves and conduction electrons. The activation energies of the relaxation processes accompanied with P_2 and P_3 were obtained as 0.009 eV and 0.09 eV, respectively. The ratio between the activation energies for P_2 and P_3 agrees well with that calculated from Seeger\u27s theory making use of the values of the critical resolved shear stress for the basal slip and the non-basal slip. Therefore, the relaxation processes related to P_2 and P_3 are confirmed to be dislocation movements in the basal plane and in the non-basal plane, respectively. In Mg-Li alloys, the activation energy increased for P_2 but decreased for P_3. In Mg-N alloys, the activation energy for P_2 was comparable with that of pure Mg. The activation energy for P_4 was about 0.5 eV, and the value was considerably higher than that of the other peaks. Therefore, the origin of P_4 probably differs from that of the other peaks