Microhardness model based on geometrically necessary dislocations for heterogeneous material

Abstract

Lamellar cast irons are known as heterogeneous materials. Their overall hardness is determined by the microhardness of their microstructure contents. This study pertains to extend the indentation size effect (ISE) analyses to these heterogeneous materials. Additionally to macrohardness tests, Vickers microindentation tests were carried out on two cast irons with fully pearlitic matrix. Tensile models for pearlitic steel with both Tabor's law and Taylor's model were introduced in the ISE analyses. Microhardness expressions of the pearlitic phase within these irons were thus obtained. The obtained expressions indicate that the tensile model and the concept of geometrically necessary dislocations (GNDs) can be used to predict the ISE of the pearlitic matrix. For this pearlitic phase, it is shown that the summation of the stresses, associated with the GNDs and SSDs, is more adequate than to consider only one work-hardening stress generated by the two types of dislocations density in the ISE study.

Keywords

• Microhardness
• Cast iron
• Dislocations
• Heterogeneous