Comparative study of ASS 316L on formability at room temperature and super plastic region

ABSTRACT

In the sheet metal industry, hot forming of high strength sheet metal alloys such as austenitic stainless steels (ASSs) are in great demand. Identifying the safe strain region is essential to avoid failures and reduce the wastage. Forming limit diagram (FLD) is a vital tool which is used to describe the maximum limit of principal strains that can be sustained by sheet metals till the onset of localised necking. These diagrams are also useful in comparing the changes in forming characteristics of the material with changes in process parameters like temperature, orientation and speed of deformation. The present study aimed at comparing the experimental FLD for ASS 316L at room temperature and 900°C by stretch forming. These specimens are cut in three different orientations (0°, 45° & 90°) to the rolling direction and experiments are conducted at a strain rate of 0.1/s. It is reported that, the specimens from rolling direction are among the stronger samples. The change in formability characteristics of ASS 316L with changes in temperatures using FLD has been observed. The optical microscopy and scanning electron microscopy is analysed to understand the fracture morphologies. The comparison between these set of results indicates that there is significant increase in formability of material.

Abbreviations ASS: Austenitic Stainless Steel; RT: Room Temperature; FLD: Forming Limit Diagram; FFLD: Fracture Forming Limit Diagram; SEM: Scanning Electronic Microscopy; LDH: Limiting Dome Height; UTS: Ultimate Tensile Strength; YTS: Yield Tensile Strength; K: Strength Factor; n: Strain Hardening Exponent

KEYWORDS:

• Austenitic stainless steel 316L
• elevated temperature
• forming limit diagram (FLD)
• scanning electron microscope (SEM)
• limiting dome height (LDH)

Acknowledgments

Authors would like to acknowledge the financial support received for this research work from All India Council of Technical Education (AICTE) file No: 8-52/RIFD/RPS/POLICY-1/2016-17 and also grant received under FIST grant (DST) file No: SR/FST/College-29/2017 for the purchase of some special equipment like SEM.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the All India Council for Technical Education file No: 8-52/RIFD/RPS/POLICY-1/2016-17 DSTfile No: SR/FST/College-29/2017