Critical Assessment 7: Quenching and partitioning

Abstract

Quenching and partitioning is a relatively new heat treatment concept to generate microstructures containing retained austenite stabilised by carbon partitioning from martensite. Research on quench and partitioning has been conducted by numerous groups, and this critical assessment provides some of the authors’ perspectives on progress and understanding in the field, with particular focus on the physical metallurgy and transformation mechanisms, process variations, mechanical behaviour, and industrial implementation. While much progress has been made, the field provides rich opportunity for further understanding and development.

Effect of Q&P parameters on microstructure development and mechanical behaviour of Q&P steels

“…Addition of elements, such as Si, retards the formation of carbides and gives rise to the carbon enrichment of austenite (Santofimia et al, 2008;Paravicini Bagliani et al, 2013). Moreover, increased manganese levels have been shown to be effective at reporting significant austenite fractions with improved tensile properties in Q&P steels (De Moor et al, 2011;Speer et al, 2014). Mechanical property studies indicate that Q&P shows significant potential to generate novel property combinations that would otherwise be difficult in low alloy compositions (Speer et al, 2014).…”

“…Moreover, increased manganese levels have been shown to be effective at reporting significant austenite fractions with improved tensile properties in Q&P steels (De Moor et al, 2011;Speer et al, 2014). Mechanical property studies indicate that Q&P shows significant potential to generate novel property combinations that would otherwise be difficult in low alloy compositions (Speer et al, 2014). Fundamental understanding of the property -microstructure relationships in this type of steels has not been achieved, which is required for further improvement of the properties via intelligent microstructural design.…”

“…Although there are already works on characterization of the steel microstructure after Q&P (Santofimia et al, 2008;De Diego-Calderón et al, 2014;De Knijf et al, 2014a;Tan et al, 2014a;Tan et al, 2014b), there is still a lack of knowledge about the strain distribution between the microstructural constituents in Q&P structures during loading in the plastic range. Low carbon TRIP steel compositions have been used to successfully generate martensitic microstructures with substantial RA levels through Q&P processing (Speer et al, 2014). Addition of elements, such as Si, retards the formation of carbides and gives rise to the carbon enrichment of austenite (Santofimia et al, 2008;Paravicini Bagliani et al, 2013).…”

Microstructure Analysis and Mechanical Properties of Low Alloy High Strength Quenched and Partitioned Steel

“…leads to unique mechanical properties. The martensite and bainite constituents contribute to an increase of strength, whereas RA provides an improvement of ductility [1]. The microstructural heterogeneity results also in significant stress and strain partitioning among the micro-constituents during plastic deformation.…”

Recent developments in bearing steels

“…25 Since then, synchrotron X-ray studies of the same have been reported 26 where it is found that carbon first partitions from martensite to austenite during tempering -this, of course, is a widely known phenomenon, 27 reflected also in the design of quenching and partitioning steels. 28 Lejay et al 29 now report results from a combination of synchrotron X-ray analysis and dilatometry where they characterise the dimensional changes and relate them to phase fractions, accounting for the measured lattice parameter changes.…”