Semi-solid plasticity and deformation control of superalloy investment casting

Abstract

The deformation in superalloy investment casting under thermal-mechanical coupled stress is causing huge waste of materials and energy. Mechanical models of both alloy and shell are essential to predict the deformation of castings accurately. The elastoplastic behavior of superalloy in semi-solid zone is critical to the deformation during solidification. In this paper, the deformation of ring-to-ring castings with Ni-based superalloy K4169 is researched. To obtain the thermal-mechanical behavior of K4169 from solid region to semi-solid zone, physical simulated uniaxial compression is performed. Yield stress and plastic modulus from the measurement are imported into the database for numerical simulation. Different thermal-mechanical models of both alloy and shell are compared. With elastoplastic model for alloy, considering the deformability of shell with elastic model, the accuracy of prediction is within CT4 level, with a maximum error of 0.39mm. The deformation of reaches the minimum when the initial temperature of alloy and shell are 1500℃ and 900℃. The research on semi-solid performance of alloy and thermal-mechanical models can provide theoretical guidance for deformation prediction. The method of this research is promising in dimensional control of castings, and can be transported to dimensional control problems upon solidification process with different kinds of materials and castings.