On Aging of Lead-rich Lead-Cadmium Alloys

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  • Pb基Pb-Cd合金の時効について
  • Pbキ Pb-Cd ゴウキン ノ ジコウ ニ ツイテ

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Abstract

The precipitation of cadmium from lead-cadmium solid solution was studied by microscopic observation, micro-hardness measurement, and specific heat measurement,with various alloys containing 1, 2, and 3 wt%Cd. (1) The precipitation of cadmium from lead takes place in two distinct stages. In the 1st stage, a cellular precipitation proceeds rapidly from grain boundary to grain center. In the 2nd stage, another cellular precipitation proceeds slowly from the grain boundary to the grain center. The lamellar spacing of cadmium in the cell of the 1st stage was considerably smaller than that of the 2nd stage. The alloy was age-hardened in the 1st stage and then softened in the 2nd stage. (2) The kinetic law for the 1st stage seems to be represented by Johnson-Mehl’s equation; f=1−exp(−btn), where f is the precipitation fraction and n is a constant independent of alloy composition and has the value of 2.9±0.2. The kinetic law for the 2nd stage seems to be represented as follows; f=K\sqrtt+C, where K and C are constants. (3) The activation energy for the 1st stage was obtained by microscopic observation as about 9 kcal/mol.

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