Development and Strength Evaluation of Ultra-fine Grain α-brass for Micromachines

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Ultra-fine grain α-brass with average grain size of 1.0μm was successfully obtained by repetitive rolling and heat-treatment. Hall-Petch relationships were found between the strengths and the grain size, and then the strengths of the ultra-fine grain material were extremely higher than that of conven-tional materials. Tensile tests and fatigue tests of thin wires of commercially pure iron were conducted. With decreasing the diameter of specimen, the yield phenomenon was disappeared and the fatigue be-havior of the thin wire was strongly dependent on the yielding. Fatigue tests of Zr-based metallic glass (BMG) were also conducted, and found that the BMG plate had inhomogeneity in the thickness direc-tion, where the strength was highest at the surface, and it was lowest in the midsection. The fatigue strength of the BMG was very sensitive to notch.