Nanoindentation response of interphase precipitation in a Nb microalloyed steel

ABSTRACT

In this work, dedicated isothermal transformation studies were performed in a Fe–C–Mn–Nb alloy to obtain two types of precipitate morphology embedded in a similar ferritic matrix. Nano-hardness of individual ferrite grain was measured by using an in situ nano-mechanical tester. The peak of nano-hardness distribution from interphase and dispersed precipitate strengthened ferrite corresponds to the nano-hardness range of 2.6–2.8 and 2.5–2.6 GPa, respectively. A wider spread of nano-hardness from interphase precipitate strengthened ferrite was observed and rationalised by considering the variation in inter-particle spacing on slip planes. The ‘pop-ins’ on the load-depth curve was not able to be correlated with the morphology of a precipitate.

KEYWORDS:

• Nb microalloyed steel
• interphase precipitate
• dispersed precipitate
• nanoindentation
• pop-in

Acknowledgements

The authors thank Ms W. Y. Xue for the analyses of the nano-mechanical tests.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Key R & D Program of China [grant number 2017YFB0304201], the National Natural Science Foundation of China [grant number 51204048] and the Fundamental Research Funds for the Central Universities [grant number N180702012].