Correlation Between Microstructure and Mechanical Properties Before and After Reversion of Metastable Austenitic Stainle
- PDF / 2,307,395 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 47 Downloads / 237 Views
ODUCTION
IN the past years, the demand for lightweight vehicles in order to reduce fuel consumption and also contaminant emissions has created interest in new materials to replace the classical carbon steel grades.[1] Austenitic stainless steels are presented as potential candidates for structural parts due to their excellent formability, weldability, and work hardening properties together with high corrosion resistance and high energy absorption capabilities. The main drawback is their relative low yield strength. It is well known that the addition of nitrogen is a way to improve mechanical properties by solid-solution strengthening.[2,3] Nevertheless, there is a limit for nitrogen solubility and problems with hot ductility may also appear. Strengthening by grain refining from dynamic recrystallization is another strengthening path, but severe deformations and high recrystallization temperatures are required.[4] Among the austenitic stainless steels, those with thermodynamically metastable austenite at room temperature can be strengthening by grain refining applying thermo-mechanical processes. The procedure involves cold deformation of austenite to form strain-induced martensite followed by short annealing to revert the martensite into austenite. The amount of martensite created depends on processing parameters such as GEMMA FARGAS, Associate Professor, ANA ZAPATA and INA SAPEZANSKAIA, Ph.D. Students, JOAN JOSEP ROA, Postdoctoral Researcher, and ANTONIO MATEO, Professor, are with the CIEFMA - Departament de Cie`ncia del Materials i Enginyeria Metallu´rgica. Universitat Polite`cnica de Catalunya (CIEFMA-UPC). Avda. Diagonal 647, 08028 Barcelona, Spain. Contact e-mail: [email protected] Manuscript submitted on December 11, 2014. Article published online September 28, 2015 METALLURGICAL AND MATERIALS TRANSACTIONS A
temperature and deformation rate,[5] as well as on the steel composition.[6,7] Numerous investigations have shown that ultrafine and even nanograined austenite microstructures obtained from heavy cold rolling shows an excellent combination of mechanical strength and ductility[8–10] and also excellent fatigue strength[11] together with a higher corrosion resistance as compared with cold-rolled steel.[12] AISI 301LN austenitic stainless steel is one of the commonly used stainless steel grades for light vehicles due to its excellent combination of formability and corrosion resistance. Thanks to its capability to transform to martensite under deformation; earlier studies have demonstrated that grain refinement up to ultrafine-grained austenite is feasible by means of reversion treatments. Those studies applied severe cold rolling deformation (45 to 77 pct of thickness reduction) to achieve final improvements in strength, ductility, and fatigue behavior.[13–16] On the other hand, a recent work carried on by Huang et al.[17] studied the effect of annealing temperature and time on the grain size of reversed austenite from 5 to 70 pct of strain-induced martensite obtained by advanced thermo-mechanical process, where
Data Loading...
