Grain character and mechanical properties of Fe-21Cr-15Ni-6Mn-Nb non-magnetic stainless steel after solution treatment

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2019-01, Vol.742, p.662-671
• Main Authors: Song, Yan-Lei, Li, Chang-Sheng, Li, Bin-Zhou, Han, Ya-Hui
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Elongation; Grain boundaries; Grain growth; Grain size; Hall-Petch; Hot rolling; Magnetic properties; Mechanical properties; Niobium; Non-magnetic stainless steel; Regeneration; Solution heat treatment; Solution strengthening; Solution treatment; Stainless steel; Twin boundaries; Twinning; Σ3 boundary
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2018.02.056

A systematic investigation on grain growth behavior, grain boundary character distribution and mechanical properties of Fe-21Cr-15Ni-6Mn-Nb non-magnetic stainless steel was performed after solution treatment in temperature range of 1100–1200 °C with various durations. The results showed the hot-rolled plate still maintained fine microstructure with the grain size range of 11.5–19.6 µm after solution treatment. A Nb(C, N) drag mechanism concurrent with a restraining effect of Σ3n boundaries during solution treatment resulted in a slow kinetics with grain growth exponent n of ~ 4. The proliferation mechanism of Σ3n boundaries mainly varied from Σ3 regeneration to new twinning accompanied by grain growth. Twin boundary has an effective strengthening role like a grain boundary. The YS, UTS and elongation of solution-treated plate was above 634.0 MPa, 838.9 MPa, 45.3％, respectively, which were superior to the conventional austenitic stainless steel. The Hall-Petch relationship was determined well between the grain size under the condition of either including or excluding twin boundaries and tensile results. An inherent relationship between k′ and k (k′ and k correspond to the circumstance of including and excluding twin boundaries, respectively), was expressed by k′=1.52037+1.67168k. [Display omitted] •The growth exponent n of ~ 4 was calculated in solution-treated Fe-21Cr-15Ni-6Mn-Nb steel plate.•A transformation from Σ3 regeneration to new twinning mechanism was observed with grain growth.•The Hall-Petch relationship was determined between the grain size of whether including(k′) or excluding twin boundaries(k) and tensile results.•A relationship between k′ and k was expressed by k′ = 1.52037 + 1.67168k.