Influence of microstructure on deformation behaviour of alloy 718

Paper in proceeding, 2014

Metal cutting of Superalloys can be problematic, partly due to the high temperature strength of the alloys. The deformation mechanisms during metal cutting are complex, and it is practically difficult to measure the local deformations and the stresses involved in the process. This results in a desire to numerically model the cutting process with e.g. the finite element method. For this an accurate material model able to describe the deformation behavior at the strain rates and temperatures occurring in the cutting process has to be developed. In this work the deformation behavior of Alloy 718 with four different microstructures has been studied i.e. aged and solution treated condition with small and large grain size. All studied microstructures are relevant for aero engines as they occur at different stages in production of different components. To study the deformation mechanisms involved in chip forming during metal cutting the alloy has been mechanically tested at various strains, strain rates and temperatures, and the resulting microstructure has been analyzed and compared with samples obtained by metal cutting. Compressive and tensile testing was performed at strain rates ranging from 0.001 to 3000 s-1 and from RT to 800°C. It was found that deformed microstructure from metal cutting experiments and mechanical testing show similar appearance, indicating that mechanical testing can be used to describe and study the deformation mechanisms occurring during metal cutting.