Mechanical Properties and Deformation Behavior of Nano/ultrafine Fe–18Cr–8Ni Austenitic Steel Processed by Low Temperature Rolling and Annealing Treatment

Abstract

In the present study, the method of phase reversion process is adopted to obtain nanograined/ultrafine-grained (NG/UFG) structure in 18Cr-8Ni austenitic stainless steel. Severe cold deformation (86% reduction) at room temperature and (64%, 86% reduction) at À50 C is carried out, followed by annealing in the conditions of 650 C-50 min and 700 C-15 min. The influence of different cold rolling and annealing conditions on the microstructure and mechanical properties of stainless steel is studied. The decrease of rolling temperature and the increase of reduction lead to the volume fraction of strain-induced martensite increase. Lath-type martensite, dislocation celltype martensite, and untransformed austenite in 64% reduction (at À50 C) and mainly dislocation cell-type structure in 86% reduction (at room temperature and À50 C) are observed. Increasing reduction or rolling temperature promotes the cold-rolled α texture of strain-induced martensite to the stable orientations. The grain size obtained is in the range of 0.4-0.89 μm, with yield strength in the range of 684-1017 MPa and high ductility of 23-54%. Deformation behavior shows that the amount of twins and stacking faults at 5 mm distance from the fracture is higher than the fracture.

Effects of Grain Size on Mechanical Properties and Work‐Hardening Behavior of AISI 304 Austenitic Stainless Steel

“…Regarding ASSs, due to the absence of a notable phase transformation during the thermal treatment, grain refinement has been achieved by static recrystallization (SRX), dynamic recrystallization (DRX), formation and reversion of strain‐induced martensite, and various severe plastic deformation techniques . In fact, many commercial ASSs are metastable against the martensitic transformation during deformation.…”

Research on Formation Conditions of the Ultrafine-Grained Structure of the Cylindrical Parts Manufactured by Power Spinning Based on Small Strains

“…This is because the number of dislocations can pile-up in the grain interior is decreased significantly when the grain size decreases to the ultrafine scale. It leads to a decrease in strain hardening ability during plastic deformation and the plastic instability phenomenon occurs easily [ 2 , 30 ].…”

“…Grain refinement is one of the most important ways of increasing the strength and plasticity of materials simultaneously [ 1 ]. The materials will exhibit excellent mechanical properties when the grain size is refined to ultrafine scale (grain size ranged from 100 nm to 1000 nm) [ 2 ]. Severe plastic deformation (SPD) is the most common method for manufacturing the materials with ultrafine grained-structure (UFG), such as equal channel angular pressing (ECAP) [ 3 ], high pressure torsion (HPT) [ 4 ], multiple forging (MF) [ 5 ], accumulative roll bonding (ARB) [ 6 ] and so forth.…”

Microstructure Evolution and Mechanical Properties of Heterogeneous Nano/Ultrafine‐Grained Austenitic Stainless Steel Prepared by Low‐Temperature Rolling and Annealing

“…This result is consistent with those in the literature. [40][41][42] In addition, the austenite and ε-martensite conformed to the S-N relationship: (111)γ∥(0001)ε, γ∥ [11][12][13][14][15][16][17][18][19][20]ε, while the α 0 -martensite and ε-martensite followed the Burgers relationship: (0001)ε∥(110)α 0 , [11][12][13][14][15][16][17][18][19][20]ε∥ [1][2][3][4][5][6][7][8][9][10][11]α 0 . The orientation relationship of austenite, ε-martensite, and α 0 -martensite satisfied (111)γ∥( 0001)ε∥(110)α 0 , [10-1]γ∥ [11][12][13][14][15][16][17][18][19][20]ε∥ [1][2][3][4]…”

“…This technology includes conventional cold rolling or cryogenic rolling and subsequent annealing treatment at an appropriate temperature. [12][13][14][15][16][17] The strain-induced martensite reversion process for developing NG/UFG steel is easy to implement and is suitable for large-scale production. In addition, optimizing the process parameters to realize the comprehensive benefits of phase transformation and controllable annealing treatment is straightforward.…”