Nobuhiro Iguchi1, Yoshiki Oka2 and Yasunori Saotome2
1Faculty of Science and Engineering, Waseda University, Tokyo
In the present investigation the transformation superplasticity in a commercial grade pure-iron has been studied by using a specially designed apparatus.
The main results obtained are as follows:
(1) The transformation superplastic phenomenon in pure-iron was observed in the range of 910 to 1100°C under a rapid heating and cooling cycle.
(2) The strain rate ( \dotγ) due to transformation superplasticity was detected to be variable in this temperature range. The maximum strain rate ( \dotγmax) was observed just about 910°C which might be the temperature of initiation of phase transformation.
(3) The total strain per cycle was proportional to the flow stress in the lower stress range.
(4) The flow stress characterized by superplasticity in pure-iron was dependent on heating rate. This dependence on heating rate might be similar to that on grain size in the micro-grained superplasticity.
From these experental results, the mechanism of transformation and transformation superplasticity would be of great use for further studies on the interface behavior at the α/γ interface and for the approach based on the rapid heating transformation theory.
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