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![The variation in retained austenite morphology as strain is increased in a quench and partition (Q&P) steel, where blocky and film-like retained austenite are highlighted in the bright field (a, b) and dark field (c, d) images respectively. The strain corresponding to each image are as follows: (a, c) 0%; (b, d) 12%. Micrographs from [36].](publication/360205181/figure/fig1/AS:11431281095845163@1668032298277/The-variation-in-retained-austenite-morphology-as-strain-is-increased-in-a-quench-and.jpg)
The variation in retained austenite morphology as strain is increased in a quench and partition (Q&P) steel, where blocky and film-like retained austenite are highlighted in the bright field (a, b) and dark field (c, d) images respectively. The strain corresponding to each image are as follows: (a, c) 0%; (b, d) 12%. Micrographs from [36].
Source publication
The stability of retained austenite refers to its resistance to transform into martensite. While most models describe the thermal and mechanical influence on retained austenite stability and transformation kinetics separately, few have considered explaining both aspects in a unified model. Here, we review the factors governing austenite stability a...
Contexts in source publication
Context 1
... shows that the influence of grain size on retained austenite stability is linked to chemical composition, which can be difficult to isolate in experiments. Figure 1 shows the block and film-like morphologies of retained austenite reported by previous authors [8,[36][37][38]. Retained austenite films are known to have higher resistance to martensite transformation under mechanical loading compared to blocks [8,37]. ...
Context 2
... morphological effects on mechanical stability are intrinsically linked to other factors governing retained austenite stability, including carbon content, stress state and strength of matrix. Xiong et al. [36] reported that retained austenite films (Figure 1(c)) were more mechanically stable than blocky austenite (Figure 1(a)) despite having a lower carbon content. The higher mechanical stability of films was owing to the surrounding lath martensite, whereas the blocks were surrounded by proeutectoid ferrite. ...
Context 3
... morphological effects on mechanical stability are intrinsically linked to other factors governing retained austenite stability, including carbon content, stress state and strength of matrix. Xiong et al. [36] reported that retained austenite films (Figure 1(c)) were more mechanically stable than blocky austenite (Figure 1(a)) despite having a lower carbon content. The higher mechanical stability of films was owing to the surrounding lath martensite, whereas the blocks were surrounded by proeutectoid ferrite. ...
Citations
... where V ∘ γ and V γ indicate initial and final austenite volume fractions after deformation, ΔG γ→α ′ is the change in the chemical-free energy, ε is the plastic strain and parameter k is a constant. The critical driving force for the martensite transformation (ΔG γ→α ′ ), depends on the concentration of alloying elements, as described in the reference [47,48]. The ΔG γ→α ′ for the present steel was calculated to be − 5497.43 ...
... Most of the previous reviews on deformation-induced transformation in steels majorly discuss the factors influencing the mechanical stability of austenite during deformation. 6,14,15,[30][31][32][33][34] and emphasize on the importance of austenite stability in tailoring the mechanical properties of the steels. Castellanos et al. 35 reviewed various thermomechanical routes to carry out the stress and strain-induced transformation in single phase fully austenitic steels and in multiphase microstructures. ...
... However, no prospective on the transformation kinetics was presented in the review. Wong 34 reviewed the thermodynamics of transformation and various factors influencing the stability of retained austenite in multiphase steels. From the kinetics point of view, the author just discussed various kinetic models and did not present any comparison among them. ...
... Hence, transformation of austenite to martensite cannot be observed in this regime and only plastic deformation of austenite can be possible. 1,33,34,41,42,[52][53][54][55] Mechanism of deformation-induced transformation of austenite into martensite Deformation-induced transformation of FCC austenite (γ) into BCT martensite (α ′ ) in ASSs is well studied by the previous investigators. [56][57][58][59][60][61] The mechanism of deformationinduced transformation of austenite into martensite involves deformation-induced lattice distortion which results in the nucleation and growth of martensite embryo within the austenite matrix. ...
Deformation-induced austenite to martensite transformation is an important phenomenon during the deformation of metastable fully austenitic transformation induced plasticity (TRIP) steels. The kinetics of austenite to martensite transformation influence the deformation behaviour of austenitic stainless steels but is often neglected by the materials community. In this paper, after an initial discussion on thermodynamics and mechanism, the importance of deformation-induced transformation kinetics is briefly outlined and the influence of various parameters like grain size, deformation temperature, strain rate, stress state and prior austenite deformation on the transformation kinetics is critically assessed. Variation of transformation kinetics with various parameters has been identified and justified. These variations could act as a ready reference for designing austenitic stainless steels with the desired set of mechanical properties and deformation behaviour. Further in this paper, selected models that can predict the transformation kinetics are reviewed and compared. In the end, research fronts related to transformation kinetics that can be further explored have been identified.
... However, catalogs or characteristic sheets of CCT diagrams do not provide complete information on austenite transformations. To establish CCT diagrams, the dilatometric method combined with metallographic investigations and hardness measurements is commonly used, but it is time-consuming and expensive Wong (2022). ...
... Some studies Wong (2022) and Kulawik et al. (2021) have applied neural networks to model the kinetics of supercooled austenite transformations, focusing primarily on the start curves or start and end curves, without considering hardness and structural components. The use of a single neural network with a complex structure often hinders the construction of a representative training set due to limited reference charts and wide ranges of input variables. ...
A low-carbon low-alloy steel was subjected to two-step quenching and partitioning (Q&P) treatments which resulted in multiphase microstructures comprising varying amounts of primary martensite, retained austenite, fresh martensite and bainitic-ferrite. The Q&P microstructures were quantified using an alternative methodology that utilized well-established semi-empirical relations and the experimental amount of retained austenite and its carbon content estimated using X-ray diffraction. The dependence of the tensile properties of Q&P samples on their microstructural features was investigated with particular emphasis on bainitic-ferrite. The best combination of strength and elongation was attained corresponding to the quenching temperature which resulted in the maximum amount of retained austenite possessing higher stability. Attempts were also made to calculate the yield strength of the Q&P steel in terms of its microstructure by considering the contributions from various strengthening mechanisms in order to understand the experimental observations. Though the calculated yield strength of the Q&P samples was slightly overestimated, the overall variation of yield strength with QT was predicted correctly. Primary martensite showed the highest contribution to the YS of Q&P microstructure for the lower QTs. The increase in the YS for the higher QTs was attributed to an increase in the amount of bainite at the expense of primary martensite.
The two‐body abrasive wear properties of metastable austenitic steels (MAS) against SiC abrasive paper are investigated at different wear loads. To ensure a metastable austenitic microstructure, the alloying compositions are chosen such that the martensite start temperature of the MAS is approximately at room temperature, while the proportions of carbon, manganese, and aluminum change. The abrasion test results are compared to martensitic (40MnB5) and austenitic steel (Hadfield steel). An up to four times lower weight loss is found for the MAS compared to the Hadfield steel and up to 6.7 times lower weight loss compared to the martensitic steel. It is found that the wear resistance of the MAS increases significantly with wear load. Wear resistance of over 1300 Nm mm−3 is achieved at the highest wear load of 32 N. The wear properties of the MAS are associated with an increase in the surface hardness resulting from a mechanically induced austenite to martensite phase transformation. It is shown that the addition of aluminum to the MAS reduces the wear resistance. This is explained by an increase in stacking fault energy and the associated restriction of the mechanically induced transformation to martensite. The two‐body wear properties of high‐carbon metastable austenitic steels (MAS) are investigated and compared to conventional wear‐resistant steels. MAS exhibit wear resistances up to five times greater than conventional wear‐resistant steels. The effect of aluminum addition on the wear properties of such MAS is investigated and discussed in terms of the related stacking fault energy.
