Abstract
Abstract The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γ transformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles decreased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.
Highlights
High-strength low-alloy (HSLA) steels are important structural materials
Austenite grain 1 gradually extended outward in different directions with the increase in temperature, such that the grain grew into the α-phase by grain boundary movement
Numerous researchers have investigated the austenite grain growth behavior using isothermal treatments [13], in situ measurements [14], and simulated mode predictions [15]. Their results indicate that austenite grains grow by boundary movement and are affected by secondary precipitates [2]
Summary
High-strength low-alloy (HSLA) steels are important structural materials They have good mechanical properties, including high strength, resistance to brittle fracture, cold formability, and good weldability. The austenite grains grow via grain boundary migration [1], which can be inhibited by the presence of particles of a second phase, thereby producing a grain boundary pinning effect [2]. This grain growth inhibition has different effects, depending on the size and fraction of precipitates [3]. The addition of a small amount of Ti can lead to the dispersion of small-sized nanoscale TiN precipitates and effectively inhibit the austenite grain growth [7]. The level of Ti addition must be carefully controlled, otherwise TiN particles will be coarse and their density will be reduced such that the austenite grains in the CGHAZ are coarsened [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Minerals, Metallurgy, and Materials
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
