In this work, the static softening behaviour of GH4500 superalloy during the two-pass thermal deformation was investigated via thermal-simulation compression experiments at the temperature range of 1293 K to 1373 K, strain rate range of 0.01 s−1 to 1 s−1 and interval time range of 0 s to 180 s. The metallographic structure acquired from optical microscope (OM) indicated that both static recovery (SRV) and post dynamic recrystallization (PDRX) would occur during the holding stage. Meanwhile, the influence of interval time, deformation temperatures and strain rates on static softening behaviour were revealed. The results showed that the softening effects principally induced by PDRX strengthened with the increase of the interval time, deformation temperatures and strain rates. To quantitatively describe the PDRX kinetic process of GH4500 superalloy, a model on grounds of Avrami kinetics was established to predict the PDRX softening fraction via eliminating the effect of static recovery. The predicted data of the PDRX softening fraction were well consistent with the experimental data, manifesting that the model could precisely evaluate the PDRX softening behaviour in the stage of inter-pass holding.

In order to study the collapse deformation mechanism of metal liner under coupling of multi-physics field, the input current was obtained through circuit design and simulation by Multisim. The results show that the peak input current is determined by the capacitor voltage. The coupling simulation of electromagnetic-thermal-mechanical field was carried out by using LS-DYNA software. The influence mechanism of liner on the collapse deformation of the metal liner is analysed. The collapse deformation of liner with cylindrical tip is different from that of traditional liner. The tip of the cylinder is beneficial to utilizing the high pressure in the centre of the cylinder. But the micro-element at the top of the cone collapse to the axis with decreasing velocity along the outer contour of the tip. For the conical metal liner with cylindrical end, the current peak needs to reach more than 2 MA to make the liner obtain sufficient collapse velocity. The collapse velocity of conical metal liner element increases with the decrease of wall thickness, while the collapse velocity of bottom liner element decreases with the increase of cone diameter and cone height.