Abstract
In a study of tempering mechanism of quenched β-tin bronze, H. Imdi reported that mechanism β→β′→β″→α+δ, assuming the two intermediate states, β′ and β″.
The present investigation was carried out to study in detail the facts which remain unexplained by means of microscopic examinations and X-ray analyses.
The results obtained are as follows:
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oindent(1) β′ is the 250° tempered state and consists (β+α) (in the case of (A) 25.44%Sn alloy) or (β+δ) (in the case of (B) 27.80%Sn and (C) 28.71%Sn).
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oindent(2) β′ microstructure of (A) alloy has two kinds of long thin parallel bands each of which has a striated furrowlike striated relief. δ appeared in the matrix and boundary of β in the case of β′ of (B) and (C) alloys.
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oindentFrom X-ray analyses, the present writer is led to believe that the above abnormal structures of β′ were produced by the plastic slip of β and β→α transformation.
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oindent(3) It is thought that β″, which resembles β′ in microstructure with the exception of easier corrosion than β′, is the changed state of β′ in atomic arrangement of the thermal distribution of electrons of β, from the facts β″ gives diffraction patterns containing lines which do not belong to β′ (β+α or β+δ) and that β″ gives the lowest specific resistance value on tempering.
