Partitioning of carbon from supersaturated plates of ferrite, with application to steel processing and fundamentals of the bainite transformation

Critical Assessment 7: Quenching and partitioning

“…1,[5][6][7][8] Austenite/martensite interfacial migration has been conceptually and quantitatively considered, 11,25,26 but further experimental studies are needed. This is because measured dilatometric expansions at low partitioning temperatures during Q&P may signify low interface mobility and little migration, bainitic growth, and/or isothermal martensite formation (below M s ), whereas dilatometric contractions at higher partitioning temperatures may correspond to reduced ferrite growth, austenite growth, and/or martensite tempering effects.…”

“…1,[5][6][7][8] The mechanism of carbon partitioning to austenite has been debated since the introduction of Q&P, primarily because the chemical and microstructural changes that occur in low alloy silicon-and/or aluminium-containing compositions designed to suppress carbide formation and promote austenite retention are difficult to monitor during processing. Additionally, final Q&P microstructures do not represent the microstructural state of low alloy compositions with elevated M s temperatures during the quenching or partitioning steps.…”

“…For example, a quench temperature selection methodology was developed to predict the maximum amount of carbon enriched retained austenite possible for a given alloy and to guide Q&P processing. 4,8 This was later extended to include carbon partitioning kinetics and local austenite stability, conceptually exploring how time dependent carbon variations in the austenite could modify final austenite fraction, [9][10][11] although application of the KoistinenMarburger 12,13 expression within a steep concentration gradient to determine local austenite fractions 9 may require further consideration and refinement. Furthermore, austenite grain size and mechanical stabilisation by the introduction of dislocation debris may affect M s temperature 13 and phase fraction predictions.…”

Microstructure and Mechanical Properties of a TRIP-Aided Martensitic Steel

“…In the past decade, some advanced high-strength and ultrahigh-strength sheet steels (AHSS and AUHSS, respectively) such as transformation-induced plasticity (TRIP) [1] -aided sheet steel [2][3][4][5][6][7][8][9][10][11], quench and partitioning steel [12,13], and twinning-induced plasticity (TWIP) steel [14] have been developed in order to reduce the weight and improve the impact safety of automobiles. General ultrahigh-strength TRIP-aided steels such as TRIP-aided bainitic ferrite (TBF) steel are produced by an isothermal transformation (IT) process at a temperature above the martensite-start temperature (M s ) or at a temperature between M s and the martensitefinish temperature (M f ) [6].…”

Novel method for refinement of retained austenite in micro/nano-structured bainitic steels

“…Previous works on the martensitic steels showed that the carbon from the supersaturated martensite can migrate to the untransformed austenite during partitioning stage [8][9][10][11] . The carbon enrich retained austenite becomes more stable as a result of this relatively short process (usually ≤0.5 hrs) 12 .…”