Abstract
The effect of the transformation superplasticity (that is a martensite transformation) on the stress releasement has been examined. In the first study, using the new apparatus (a restraint thermal cycle test) by which the displacement of only the transformed part of the specimen can be measured, the proportion between transformation superplasticity and transformation expansion on the amount of the stress releasement was examined. The new composite specimen of which the test 9%Ni steel was joined by friction welding to SUS304 stainless steel on the both ends was also used.
The results are shown as follows;
1) The expansion by only transformation superplasticity was separated from whole expansion during transformation using the new apparatus and specimen.
2) When the much amount of thermal stress is generated in spite of a small transformed area, the stress releasement during transformation chiefly occurs by transformation superplasticity.
3) Regard as stress releasement in the midst of cooling just after transformation start, it mainly occurs by superplasticity because of its high thermal stress. But, in the latter half of the transformation, the stress releases mainly by transformation expansion.
4) The proportion of the transformation expansion and superplasticity was measured.
