Stress evolution in graded materials during densification by sintering processes

A set of constitutive laws for describing functionally graded materials behaviour during entire sintering process was developed. It can be used to get stress distribution arising during sintering and cooling as well as to check various parameters on sintering of FGM (particle size, density and graded profile of concentration) to optimise the process. It was implemented in ABAQUS code as user subroutine UMAT and fully coupled with heat transfer. Examples of WC–Co functionally graded cone were simulated. The numerical results show that the stresses in functionally graded cone during heating, isothermal holding and cooling have significant differences. Those mismatch stresses caused by differences in densification kinetics and physical properties could contribute to cracks formation at the different location of FGM part and at different sintering stages. This simulation results could be used for a better understanding of the reason of sintering defects such as cracks, and for optimisation of sintering process.