Effect of Second Phase on the Tensile Properties of a High‐Mn High‐Al Austenitic Lightweight Steel Processed by Thin‐Strip Casting

Abstract

The effects of the second phase on the tensile properties of a high‐Mn high‐Al austenitic lightweight steel processed by thin‐strip casting and subsequently aged at 600 °C for different times are studied. Depending on the aging time, the second phase includes short‐range ordered (SRO) phase, nanosized κ phase, and/or microsized κ phase. At aging time of 1 min, the 2 nm SRO phase precipitates and evolves into 6 nm intragranular κ phase when the time is 60 min, and microsized intergranular κ phases exist at austenite grain boundaries at aging time of 480 min. The precipitation of SRO phase increases the yield strength from 470 to 610 MPa, and the elongation only decreases from 55.9% to 52.1%, with ductile fracture for 380 MJ m−3. Although the precipitation of intragranular κ phase increases the yield strength to 910 MPa, but elongation decreases to 33.4%, there is a mixture of ductile and brittle fracture for 316 MJ m−3. The presence of intergranular κ phase increases the yield strength to 960 MPa, but reduces the elongation to only 3.6% with brittle fracture for 35 MJ m−3. All the second phases reduce strain hardening rate, and SRO has smaller effect.