純銅の中間温度脆性に対する検討

抄録

The ductility at intermediate temperatures has been examined for several copper specimens having grain size of 0.3-0.4 mm, paying attention to the amount of impurity of sulfur dissolved in the matrix. Tension tests were conducted at temperatures ranging from 473 K to 723 K at strain rates from 4.6×10⁻⁴ s⁻¹ to 4.6×10⁻² s⁻¹. In commercially available pure copper containing about 6 mol ppm S, the well-known phenomenon of intermediate temperature embrittlement was observed to appear at about 623 K at a low strain rate. However, the embrittlement became negligible, as the amount of impurity of sulfur decreased. It was found that the embrittlement entirely disappeared in the pure copper specimen containing S less than 1 mol ppm and, for instance, in the specimen prepared by adding 12 mol ppm Ti to commercial pure copper, and that dynamic recrystallization during the tests at intermediate temperatures occurred markedly in these specimens. Based on these results, it was concluded that the intermediate temperature embrittlement is not an inherent phenomenon in “pure” copper.