Effect of prior austenite characteristics on mechanical properties of thermomechanically processed multiphase TRIP assisted steels

Abstract

To develop any multiphase transformation induced plasticity (TRIP) assisted steel through thermomechanical processing routes, the effects of materials and process variables are to be thoroughly identified. Accordingly, the present work was programmed to study the influence of the state of prior austenite on the subsequent transformations and the related final phase combinations. In this framework, using a low carbon TRIP assisted multiphase steel, the compression specimens were subjected to different thermomechanical processing schedules to generate different prior austenite characteristics. The results indicated that the characteristics of martensite/austenite (M/A) microcomponent in the final microstructure were dictated by the state of prior austenite. In fact, increasing prior austenite grain size led to large decrease in the amount of M/A phase and this, in turn, resulted to higher strength without sacrificing the ductility. It was also found that static recrystallisation of austenite brings about more percentage of M/A phase compared with dynamic recrystallisation.

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

“…The holding of the samples at 1250 °C for 300 s resulted in a prior austenite structure (with an average grain size of 80±27 μm) similar to that after strip casting. Although the deformation temperature of 1050 °C was above the nonrecrystallisation temperature (T nr ) for this steel grade (around 950 °C [4,33,42]), the dynamic recrystallisation should not have happened, due to the small amount of deformation. This can be supported by a result published in Ref.…”

Strain-induced ferrite formation and its effect on mechanical properties of a dual phase steel produced using laboratory simulated strip casting

“…The effect of deformation temperature on the nucleation and growth of ferrite in the present DP steel is schematically illustrated in Fig. 14 [22,45,47,50,51]. Deformation at 1050 °C, which is above T nr ≈ 950 °C [13,14,16], resulted in static recrystallisation, decreased PAGS and increased prior austenite grain boundary areas available for polygonal ferrite nucleation. Deformation at 950 °C, which is near T nr , resulted in pancaked austenite and elongated polygonal ferrite and second phase regions as seen in Fig.…”

“…resulting in microstructure refinement [13,14]. When the deformation temperature is below T nr , the microstructure is further refined due to the increased number of polygonal ferrite nucleation sites in the interior of the pancaked austenite grains [15,16].…”

Microstructure Development and Mechanical Properties of Low-Silicon-Content TRIP-Assisted Steels after Coiling Process

“…Those parameters, which were kept constant throughout the deformation or cooling program, have been optimized elsewhere. [10][11][12][13][14] Microstructural features of samples were analyzed using optical and scanning electron microscopy. Specimens were electrolytically polished and then prepared using a particular tint etching method, adopted from Le Pera's technique.…”

“…[10][11][12][13][14] Thus, the present work aims at investigating the effect of bainitic transformation time and temperature on microstructural development and resulted mechanical properties in a thermomechanically processed TRIP-assisted steel with reduced amount of silicon content.…”