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

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 degrees 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 mu m after solution treatment. A Nb(C, N) drag mechanism concurrent with a restraining effect of Sigma 3(n) boundaries during solution treatment resulted in a slow kinetics with grain growth exponent n of similar to 4. The proliferation mechanism of Sigma 3(n) boundaries mainly varied from Sigma 3 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.