Phase Transformation and Annealing Behavior of SUS 304 Austenitic Stainless Steel Deformed by High Pressure Torsion

Abstract

SUS 304 austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation to give a two phase structure of austenite (γ) and martensite (α') by the transformation γα'. The phase transformation was accompanied by an increase in hardness (Hv) from 1.6 GPa in the as annealed form to 5.4 GPa in the deformed state. Subsequent annealing in temperature range 250oC to 450oC resulted in an increase in both α' volume fraction and hardness (6.4 GPa). Annealing at 600oC resulted in a decrease in α' volume fraction hardness.

Formation of epsilon martensite by high-pressure torsion in a TRIP steel

“…It was shown that charging the steels with hydrogen reduced the volume of martensite [13]. An austenite to martensite (γ → α') transformation was also reported in a SUS 304 steel processed at a low rotation rate [14]. A phase transformation in HPT was observed in an A220 steel with a composition similar to 316L steel.…”

“…In this operation, a sample in the shape of a thin disc is compressed between rigid anvils and subjected to torsional straining. Processing by HPT has been used with iron [5,6] and different steels [6][7][8][9][10][11][12][13][14][15][16], including twinning induced plasticity steels [17][18][19] which also exhibit very high uniform elongations at room temperature. A review of these data shows that different effects were reported during the processing of iron and steels by HPT.…”

The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

“…UFG (Ultrafine-grained) as well as NG (nano-grained) materials have been produced by reversion annealing of AISI 304, AISI 304L, and less stable AISI 301LN and AISI 201 metastable stainless steels, where the material strength is enhanced with a moderate decrease in plasticity. [23][24][25][26][27][28][29] Grain refinement via reversion annealing still draws attention, i.e., Sun et al [30] reported diffusive reversion of strain-induced martensite during annealing in the range of 823 K to 923 K (550°C to 650°C). [30] This paper reports the formation of SIM during the tensile test at different temperatures, and the reverse transformation analysis by the use of DSC, in-situ X-ray diffraction, and dilatometry.…”

A Significant Improvement in the Mechanical Properties of AISI 304 Stainless Steel by a Combined RCSR and Annealing Process

“…The volume fraction of deformation-induced martensite depends on different parameters, such as the applied strain, temperature, [13] initial grain size, [9,14] as well as applied stress state, and strain rate. Various techniques, such as equal channel angular pressing (ECAP), [25][26][27][28][29] high pressure torsion (HPT), [30,31] accumulative roll-bonding (ARB), [32,33] constrained groove pressing (CGP), [34] constrained groove rolling (CGR), [35] and repetitive corrugation and strengthening (RCS) [36][37][38] have been well developed. [17][18][19] Because of low SFE of AISI 304 steel (21 mJ m À2 ), [20,21] deformation bands including mechanical twins and e-martensite (hcp) are produced, which results from overlapping of stacking faults in each second {111} g plane.…”

“…[24] Recently, severe plastic deformation (SPD) techniques for producing highly strained materials have been highly appreciated. Various techniques, such as equal channel angular pressing (ECAP), [25][26][27][28][29] high pressure torsion (HPT), [30,31] accumulative roll-bonding (ARB), [32,33] constrained groove pressing (CGP), [34] constrained groove rolling (CGR), [35] and repetitive corrugation and strengthening (RCS) [36][37][38] have been well developed.…”