Microstructural stability of Ta minor-alloying HR3C stainless steel at 973 K

Publication date: Available online 14 October 2019Source: Materials Chemistry and PhysicsAuthor(s): Yang Lu, Qing Wang, Donghui Wen, Chuang Dong, Ruiqian Zhang, Peter K. LiawAbstractThe present work investigates the influence of minor-alloying element Ta on the microstructural evolution and mechanical properties of HR3C ASS (Fe-25Cr-22Ni-0.4Nb-0.18N-0.07C, wt. %) at elevated temperatures. Alloy ingots are prepared in a vacuum arc furnace and then hot-rolled, solid-solutioned at 1423 K/0.5 h, stabilized at 1173 K/0.5 h, and finally aged at 973 K for different hours (25 ∼ 408 h). The microstructure and precipitated phases in different heat-treatment states are characterized with optical microscopy (OM), scanning electron microscopy (SEM), X-ray fluorescence spectrometer (XRF), electron probe microanalysis (EPMA), and transmission electron microscope (TEM), respectively. The experimental results show that Ta minor-alloying can suppress the precipitation of brittle σ and Cr23C6 phases effectively, as evidenced that only a few of σ and Cr23C6 particles appeare on the grain boundaries after 408 h aging, exhibiting a high microstructural stability. It is attributed to the amount of Nb and Ta elements, which satisfies the composition rule that the molar ratio of (Nb + Ta)/C is 1/1. In addition, the micro-hardness of Ta-modified alloys doesn’t vary significantly with the aging time, which are consistent with the high microstructural stability. The strengthening mechanisms of sta...
Source: Materials Chemistry and Physics - Category: Materials Science Source Type: research