抄録
The deformation and transformation behavior of a maraging TRIP (TRansformation Induced Plasticity) steel (MAVAL X12) is studied experimentally. The stress holding test under cooling and the strain-controlled isothermal loading test are performed with the thin-walled tubular specimens in order to get the dilatation curves under a constant hold stress and the stress-strain curves. The existence of the back stress is confirmed since the dilatation curves do not close after a heating/cooling thermal cycle. Its value in the axial direction is determined to be 28.4MPa by means of the dilatation curves under applied hold stresses. The transformation-start condition is identified to be a linear Clausius-Clapeyron line both under tensile/compressive and shear stresses. The temperature-dependence of the yield stress determined by means of the tension, compression and torsion tests is charactered by the following: In the higher temperature range the measured values mean the yield stress of the parent phase, whereas in the low temperature range they exhibit the “composite effect, ” since the microstructure is consisted of the hard thermally-and stress-induced martensite phase and the soft parent phase. In the middle temperature range the measurement shows the result of the competition of both effects.
