Localized Strain Analysis of Ce- and Mg-Treated Cast Iron under Uniaxial Compression

Subhojit Chakraborty,Jessica Friess,Joseph Indeck,Philipp Steinmetz,Amber L Genau,Kavan Hazeli

doi:10.3390/met10121638

Subhojit Chakraborty, Jessica Friess + Show 4 more

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https://doi.org/10.3390/met10121638

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Abstract

Cast iron exhibits a wide range of mechanical properties, depending on its microstructural features. The microstructure of cast iron consists of several microconstituents with different elastic-plastic behavior, making the strain non-uniform across the bulk material. To understand the individual effects of these microconstituents on the overall mechanical behavior, local strain analysis using digital image correlation analysis was carried out. Samples with two different compositions (varying cerium, magnesium and silicon) were processed at different solidification velocities in a Bridgman furnace. Sections of the directionally solidified samples were loaded under uniaxial compression to measure global and local strain behavior. Despite the variability of the microstructure, the stress–strain curves obtained by digital image correlation (DIC) were found to react in a well-controlled way to changes in solidification velocity. It was observed that high-strain failure (greater than 15%) was accompanied by local straining of the softer ferritic phase, but during low-strain failure, local straining was not prominent. Higher nodularities, due to higher solidification velocities, raised the compressive strength without affecting the toughness significantly. Higher percentages of carbides led to higher compressive strengths with corresponding losses in ductility. The continuity of the matrix was also found to play an important role in the behavior during compression.

Highlights

Cast iron can exhibit a wide range of mechanical properties, depending on the specific microstructure and phases found in the final part [1]
Using digital image correlation (DIC) analysis, this study aims to improve understanding of the deformation behavior of gray and spheroidal cast iron under compression
Global and local strain values under quasi-static compressive loading were measured with DIC

Summary

Introduction

Cast iron can exhibit a wide range of mechanical properties, depending on the specific microstructure and phases found in the final part [1]. The microstructure of cast iron consists mainly of two microconstituents: the metallic matrix, which is mostly ferritic or pearlitic, and the carbon-rich phases, which can either be graphite or cementite (Fe3C). Research on mechanical behavior has shown that increasing the volume fraction of retained austenite (γ) or ferrite (α) increases the toughness and ductility but decreases the strength of the solidified material [2,3]. Fe3C is a relatively hard phase which increases strength but decreases ductility and toughness. The size, morphology and distribution of graphite within the matrix influences the mechanical properties [5]

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