Evaluation of changes in X-ray elastic constants and residual stress as a function of cold rolling of austenitic steels

Abstract

Austenitic steels rapidly attain high mechanical strength when subjected to cold working. The heterogeneous plastic deformation produced in cross section of the specimen, development of preferred orientation and martensitic transformation contribute to the occurrence of residual stress in cold worked steels. AISI 304 and 316 steels were cold rolled at room temperature from 10% up to 70% deformations in steps of 10%. The formation and sigmoidal growth of martensite caused by cold rolling (CR) 304 steel was studied by X-ray diffraction. The residual stresses generated were evaluated in both the austenite and martensite phases using sin 2 y technique. The accurate determination of residual stress by X-ray diffraction requires experimental determination of X-ray elastic constants for both the austenite and martensite phases. The changes in X-ray elastic constants as a function of CR of 304 and 316 steels were measured and their effect on residual stress values was established. The results show that tensile stress was generated initially on cold working in the austenite phase in both steels and in the dominant martensite phase in 304 steel, which decreases, passes through zero and becomes compressive at higher deformations. X-ray elastic constants were found to decrease in all cases and a maximum reduction of 15% was found. MST/5818

Influence of Cold-Worked Structure on Electrochemical Properties of Austenitic Stainless Steels

“…Similar observations were also reported earlier. [16] The surface preparation procedure for electrochemical studies, which includes mechanical polishing up to 1200 grit SiC paper, was noticed to modify the residual stress of both types of stainless steels and are presented in Table V. The compressive stress of a¢-martensite phase was changed to tensile stresses, while the austenite phase continued to remain under tensile stresses below 70 pct reduction and changed to tensile stress at and above it.…”

“…For converting strain measured by XRD, the X-ray elastic constant (1 + m)/E was used, where E is YoungÕs modulus and m is PoissonÕs ratio. To calculate residual stress, an X-ray elastic constant value of 3.25 · 10 -5 (kg/mm 2 ) -1 and 2.62 · 10 -5 (kg/mm 2 ) -1 [16] was used at small and large deformations, respectively.…”

Influence of strain-induced phase transformation on the surface crystallographic texture in cold-rolled-and-aged austenitic stainless steel

“…For converting strain measured by XRD, the X-ray elastic constant, (1 ϩ )/E, where E is the Young's modulus and is the passion ratio, were used. At the small deformation 3.25 ϫ 10 Ϫ5 (kg/mm 2 ) Ϫ1 and at the large deformation 2.62 ϫ 10 Ϫ5 (kg/mm 2 ) Ϫ1 , [19] X-ray elastic constant values were used to calculate the residual stress. Specimens of 3 ϫ 3 cm in size were cut from the rolled sheet material for texture measurements.…”

Study of strain induced martensite formation in a Ti modified 316 stainless steel bellow by transmission electron microscopy

“…It can form through the sequence of J o H martensite o Dc martensite [21] or J o mechanical twins o Dc martensite [5]. With increase in SFE, the deformation mode changes from H martensite to deformation twinning and then to slip [22]. Hence, in SS 304 with low SFE [14] (9.2-32.5 mJ/m 2 ) H martensite has been observed while in SS 316 with high SFE [14] (34.6-80.7 mJ/ m 2 ) deformation twinning has been observed.…”