双ロール法で作製したNi基超合金急冷薄帯の超塑性現象

概要

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The superplasticity of rapidly solidified cast-type Ni-base superalloy melt-spun ribbons which have columnar grains was investigated. Melt-spun ribbons, about 80μm in thickness, were made by a twin roll process. Superplasticity was investigated in terms of peak flow stress, elongation of specimens, and strain rate sensitivity "m" by tensile tests carried out various strain rates at 1000°C and 1100°C. The maximum m was found to be about 0.70 and its maximum elongation was larger than 360%. (360% is limit of tensile test machine used in this study.) The microstructure of specimen after high temperature tensile test was observed, and still composed of columnar structure. From these results, it was found that fine columnar structure materials exhibited superplasticity as well as equi-axial grain structure in special conditions.