| Title |
Mechanical Properties of Ultrafine Grain ( α' + γ ) Two Phase Stainless Steels |
| Authors |
김영환(Y . H . Kim) ; 안용식(Y . S . Ahn) ; 정해용(H . Y . Jeong) ; 강창용(C . L . Kang) ; 정병호(B . H . Jeong) ; 김창규(C . G . Kim) |
| Abstract |
The mechanical properties in a series of low carbon Fe-(15.5∼18.5)%Cr-10%Ni ternary stainless steels with two phase structure of deformation-induced martensite(α′) and reversed austenite(γ) after annealing for 0.6ks in the temperature range of 750 to 1100K were investigated as a function of α′ content and γ stability with transformation-induced plasticity(TRIP). All the steels almost transform to lath α′ from γ by 90% cold rolling and show α′ structure below γ content of 10%. The increase of Cr contents increases γ stability and hence decreases γ′ content in the same reduction of area. The deformed α′ rapidly reversed to γ in the temperature range of 773 to 873K and then the reversion was completed at about 1073K. The reversed γ has a ultrafine grain diameter of 0.5㎛. As a result of ultrafine grain structure of γ, the (α′ + γ) mixed structure was more stabilized. The good combination of high strength and elongation was obtained from the mixed structure containing a higher amount of retained α′ with decreasing Cr content. For example, for 15.5%Cr-10%Ni steel the proof stress of 0.79GPa and ultimate true tensile stress of 1.06GPa were obtained with elongation of 30%. The elongation caused by TRIP in the mixed structure was greatly affected by transformation behavior to α′ from γ in the initial stage of deformation. |