Optimization of 316 stainless steel/alumina functionally graded material for reduction of damage induced by thermal residual stresses

Development of material damage due to the thermal residual stresses in a 316 stainless steel/Al2O3 functionally graded material [FGM] model system during cooling from the processing temperature (900°C) has been analyzed using the commercial finite element package ABAQUS. Specifically, the effect of the material concentration profile of a 316 stainless steel/Al2O3 graded layer between the pure 316 stainless steel and pure Al2O3 regions on redistribution and reduction of thermal residual stresses and material damage has been investigated. For each condition of the interlayer material concentration profile analyzed, the stress and damage reductions have been quantified by comparing the magnitudes of specific stress components and damage parameters (interface decohesion, porosity, loss of materials stiffness, etc.) with their counterparts in the nongraded (sharp interface) 316 stainless steel/Al2O3 case. An optimization analysis of the concentration profile showed that the maximum stress and damage reductions are achieved for nonlinear material concentration profiles represented by the material concentration exponent p=4. In this concentration profile the largest gradient in the material properties is located in the metallic portions of the graded region characterized by the lower values of the Youngʹs modulus and higher plasticity.