Martensitic Transformation Induced by B2 Phase Precipitation in an Fe-20 Ni-4.5 Al-1.0 C Alloy Steel Following Solution Treatment and Subsequent Isothermal Holding
Year: 2025
Type: article
Abstract: Phase transformations significantly influence the mechanical properties of Fe-based alloys, making their understanding essential for the design of high-performance alloy materials. This study investigates microstructural evolution and martensitic transformations induced by B2 phase precipitation in an Fe-20Ni-4.5Al-1.0C (wt.%) alloy. The alloy was solution-treated at 1100 °C, followed by isothermal holding between 750 °C and 1000 °C, and water quenching. Microstructural analysis revealed that the as-quenched alloy consisted of a single-phase austenite (γ). Isothermal holding led to the precipitation of a (Ni,Al)-rich B2 phase within the grains and along grain boundaries. An α′-martensitic phase was also observed within γ-grains adjacent to the B2 precipitates in the isothermally held samples. Martensitic transformation is attributed to localized nickel depletion in the matrix surrounding B2, which reduced γ-phase stability and raised the martensite start temperature (Ms), promoting γ-to-α′ transformation during cooling. The co-existence of B2 and α′ phases significantly increased the hardness of the alloy, with a maximum observed at an 850 °C holding temperature. At higher temperatures, coarsening and partial dissolution of B2, as well reduced martensite formation, led to a decline in hardness. These findings highlight the role of B2 precipitation in promoting martensitic transformation and optimizing mechanical properties through controlled heat treatment.
Source: Metals
DOI: 10.3390/met15101135
Authors: Rosemary Chemeli Korir, Yen-Ting Huang, Wei-Chun Cheng
Institution: National Taiwan University of Science and Technology
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W4415117885