A new approach to etching low‐carbon microalloyed steels to reveal prior austenite grain boundaries and the dual‐phase microstructure

Rodriguez-Galeano, Karol F; Romano-Acosta, L. F.; Palmiere, E.J.; Rainforth, W.M.

doi:10.1111/jmi.13153

“…The analysis was conducted in the FEI Inspect F50 microscope using a voltage of 20 kV and a step size of 0.1 µm. For the observation of the prior austenite grain boundaries (PAGBs), polished samples prepared following on from other published research [25][26][27], and were etched between 1 and 3 min in a saturated aqueous picric acid solution at 80 • C until PAGBs were revealed, the solution was prepared with 100 mL of distilled water, 1.5 g of Sodium dodecyl sulphate as a surfactant and 5 to 7 drops of HCl. The average grain size and recrystallisation fraction were estimated for each deformation condition using at least 3 OM images, the average grain size was obtained with the linear intercept method (ASTM E-112) whereas the recrystallised fraction was determined with the point counting method.…”

Section: Metallographic Evaluationmentioning

confidence: 99%

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel during Controlled Hot Deformation

Martínez,

Palmiere

2024

Metals

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A series of plane strain compression tests were carried out in order to simulate the thermomechanical controlled processing of a 0.09wt% Nb low carbon steel, in a scheme of multipass finish rolling at 950 °C with interpass times of 10 s. It was observed that after the first two finishing passes a remarkable grain refinement can be achieved, since the recrystallisation was fully suppressed and abundant ultrafine ferrite was transformed dynamically during the deformation. The addition of a third finishing pass however, led to partial recrystallisation. A deep characterisation of the dynamic ferrite was carried out by diverse methods conducting to relevant findings that contribute to a better elucidation of the dynamic transformation. The results obtained indicated that the dynamic formation of a colony of Widmanstätten ferrite plates during deformation, initiates with the formation of a pair of self-accommodating plates followed by face-to-face sympathetic nucleation of new plates at one of the faces of the pairs of plates already formed. Furthermore, the crystal orientation within the dynamic ferrite phase was analysed with EBSD, it was observed that during the coalescence of plates, prior to the full polygonisation of grains, the ferrite adopts a transitory morphology which possesses particular crystallographic characteristics.

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“…The analysis was conducted in the FEI Inspect F50 microscope using a voltage of 20 kV and a step size of 0.1 µm. For the observation of the prior austenite grain boundaries (PAGBs), polished samples prepared following on from other published research [25][26][27], and were etched between 1 and 3 min in a saturated aqueous picric acid solution at 80 • C until PAGBs were revealed, the solution was prepared with 100 mL of distilled water, 1.5 g of Sodium dodecyl sulphate as a surfactant and 5 to 7 drops of HCl. The average grain size and recrystallisation fraction were estimated for each deformation condition using at least 3 OM images, the average grain size was obtained with the linear intercept method (ASTM E-112) whereas the recrystallised fraction was determined with the point counting method.…”

Section: Metallographic Evaluationmentioning

confidence: 99%

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel During Controlled Hot Deformation

Martínez,

Palmiere

2023

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The effect of the increased strain per pass during the hot-rolling and its effect on the tensile properties of V-Mo and Cr-V-Mo microalloyed dual-phase steels

Rodriguez-Galeano,

Nutter,

Azakli

et al. 2024

J Mater Sci

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It is well known that the thermomechanical processing parameters affect the mechanical properties of dual-phase (DP) steels, but optimization still remains a key challenge. This work studied two interphase precipitation-strengthened DP steels based on V, Mo, and V, Mo, Cr microalloy additions. Hot-rolling was performed with a strain per pass of 0.2 and 0.4 before isothermal transformation at temperatures between 600 and 690 °C to determine the effect of these process parameters on microstructure, particularly interphase precipitation. The microstructure was carefully correlated with the mechanical properties. It was found that a higher strain during hot rolling increases the transformation kinetics of austenite to ferrite and also increases the volume fraction of the interphase precipitation within it, leading to higher strength values. The reaustenitization temperature before the isothermal transformation also plays an important role, with increased temperature reducing the segregation banding effect and increasing the amount of ferrite. The optimal reaustenitization temperature depends on the composition, being 1250 °C for the microalloyed steel with Cr additions and 1150 °C for the Cr-free microalloyed steel. A new method was used to calculate the yield strength of these DP microalloyed steels, including the strengthening contributors of each phase and the banding effect brought into one single expression that matches the experimental results.

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A new approach to etching low‐carbon microalloyed steels to reveal prior austenite grain boundaries and the dual‐phase microstructure

Cited by 7 publications

References 17 publications

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel during Controlled Hot Deformation

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel during Controlled Hot Deformation

Microstructural Evolution in a 0.09% Niobium Low Carbon Steel During Controlled Hot Deformation

The effect of the increased strain per pass during the hot-rolling and its effect on the tensile properties of V-Mo and Cr-V-Mo microalloyed dual-phase steels

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