Three-dimensional atom probe microscopy study of interphase precipitation and nanoclusters in thermomechanically treated titanium–molybdenum steels

Interphase Precipitation – An Interfacial Segregation Model

“…However, as Murakamai et al 14) pointed out the pinning force from precipitates as small as 1 nm (in the order of 6 J mol − 1 ) would be relatively insignificant compared to the driving force for ferrite transformation. The relative insignificance of the pinning force of precipitates during the γ→α + MC transformation by the formation of carbide precipitates is further evidenced by the recent 3D atom probe tomography studies by Mukherjee et al 25,26) Where, in the case of a Ti-Mo micro-alloyed steel, only a few fully developed interphase precipitates were found in the microstructure quenched immediately after the transformation. On the other hand, nano-clusters coherent with ferrite matrix, especially when the interphase boundary mobility is high, were found in significantly higher quantities.…”

“…Additionally, inherent inaccuracies and subjective interpretation in the assessments used for the creation of the multicomponent thermodynamic database used may be influential. Furthermore, as explained by the atom probe study of Mukherjee et al 25,26) the formation of interphase precipitates becomes more significant as the interphase boundary slows. Therefore, a pinning force exerted by the precipitates upon the interphase boundary may become increasingly significant in the latter stages of the transformation.…”

Evaluating Strengthening and Impact Toughness Mechanisms for Ferritic and Bainitic Microstructures in Nb, Nb-Mo and Ti-Mo Microalloyed Steels

“…The differences between interphase and random precipitation have also been investigated by in-situ nanomechanical testers, evaluating the influence of both types of precipitation on the dislocation movement in ferrite grains and on nanomechanical properties [24]. A study carried out by Mukherjee et al [25] also revealed the coexistence of nanoclusters and precipitate particles. They determined that a bimodal distribution of larger (8-10 nm) precipitates coexisted with smaller nanoclusters (3 nm) within the interphase sheets/rows.…”

A phase-field model for interphase precipitation in V-micro-alloyed structural steels

“…Mukherjee et al demonstrated by APT, studies that the partitioning behaviour of 80 interphase precipitates greatly depends on the alloying elements [31,32]. Here, a four sub-lattice model was employed in order to make the interchange between Fe and Mn atoms possible during the computation.…”

“…The value of the gradient coefficient β was 3.8 × 10 −16 J/m. This value was 115 observed by atom probe analyses [31] for multicomponent systems and gives the interphase interfacial diffuse chemical profile equating to ∼ 3 nm. The values for both coefficients α and β was considered to be the same for all phases involved for the sake of simplicity and in order to develop on single free energy function to describe the evolution.…”