Effect of austenisation temperature on bainite transformation below martensite starting temperature

ABSTRACT

Effects of austenisation temperature on martensite and bainite transformation behaviour, microstructure, and mechanical properties of a bainitic steel austempered below martensite starting temperature were investigated in this study. Results show that the amount of athermal martensite gradually increased with the increase of austenisation temperature, whereas the amounts of bainite and retained austenite initially increased and then decreased, resulting in the trend of the first increase and then decrease in the product of tensile strength and elongation. In addition, the transformation rate of isothermal bainite after athermal martensite formation revealed a trend of deceleration and then acceleration with austenisation temperature at the beginning period. Moreover, the size of bainite plates decreased first and then increased with austenisation temperature.

KEYWORDS:

• Austenisation temperature
• below martensite starting temperature
• transformation kinetics
• microstructure
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial supports from the National Nature Science Foundation of China [Nos.51704217, 51874216], the Major Projects of Technological Innovation in Hubei [No.2017AAA116], Hebei Joint Research Fund for Iron and Steel [E2018318013] and the State Scholarship Fund of China Scholarship Council.