鉄-1, 3および5%ニッケル合金の降伏および流れ応力

Abstract

Iron-1, 3 and 5 per cent nickel alloys were melted paying attention to have the same chemical composition except nickel. Most studies were performed on the lower yield stress as the function of testing temperature, cross head speed and grain diameter, and on the measurement of the elastic constants. The results obtained were as follows:1) When tests were performed at room temperature with the cross head speed of 0.5 mm/min, the lower yield stress was raised by 8.5 kg/mm2 with increasing the nickel concentration from 1 to 5 per cent. This crement was caused by raising the frictional strees for the dislocation motion.2) The rate of work hardening of iron-1 to 5 per cent nickel alloys at room temperature was in the same range of 1.2 kg/mm2/0.01 true strain.3) The lower yield stress at -196°C was decreased by 8.8 kg/mm2, when the nickel concentration increased from 1 to 5 per cent. This decrement was due to lowering of the frictional stress.4) The cross head speed dependence of the lower yield stress was diminished by the addition of nickel.5) The flow stress was increased in the same way as the lower yield stress when the testing temperature was lowered from room temperature to -196°C.6) The interaction energy between an edge dislocation and a nickel atom by the size misfit effect was calculated as -0.012 ev, and that between a screw dislocation and a nickel atom by the modulus misfit effect was as -0.007 ev. The solution hardening observed at room temperature was considered to be due to these interaction mechanisms.7) The rigidity modulus of iron-nickel alloys was decreased by about 5-5 per cent when nickel concentration increased from 0 to 5 per cent. It is supposed that the change of the cohesive force which causes the decrease of the rigidity modulus brings about the diminution of the Peierls force, which is one of the factors of the solution softening observed at low testing temperature.