Effect of Aging on the Fracture Behavior of Lean Duplex Stainless Steels

Abstract

The influence of aging in the range of 550°C to 850°C for 5 to 120 minutes on the impact fracture behavior of 2101 and 2304 lean duplex stainless steels (DSS) was investigated in the present study. The 2304 steel displayed ductile behavior irrespective of aging conditions. In contrast, the 2101 steel displayed a ductile behavior only in the case of aging for 5 minutes at 550°C and 650°C, whereas in all other cases, it fractured in a brittle manner. The brittle fracture behavior of the 2101 steel has been attributed to the precipitation of small black particles at the a/a and a/c grain boundaries (nitrides), which form paths for easy crack propagation. In the 2304 steel, such particles precipitated at 750°C and 850°C, but they were located inside the austenitic grains because of the formation of secondary austenite. They therefore did not embrittle the steel. The larger Ni content of the 2304 steel favored the formation of the secondary austenite that is absent in the 2101 steel.

Investigation on Solid-State Phase Transformations in a 2510 Duplex Stainless Steel Grade

“…On the other hand, in 2101 and 2304 Lean DSSs, which are low-alloyed DSSs in comparison with the standard grades, such intermetallic phases have not been detected. The reduction of nickel and mainly of molybdenum contents seems to avoid precipitation of both χ-phase and σ-phase, as only chromium nitrides have been observed [16].…”

Deformation behavior of lean duplex stainless steels with strain induced martensitic transformation: Role of deformation mechanisms, alloy chemistry and predeformation

“…The most recent developed lean duplex grades use Mn as the main austenite stabilizer to minimize the addition of Ni [3][4][5][6]. This provides an increased strength / elongation potential, however at the expense of a lower resistance to corrosion and fracture as well as to longterm ageing [7,8]. With intermediate levels of Ni, lean duplex grade 1.4362 (UNS S32304), employed in construction applications [9,10] contains a Cr content of the order of 22%, a Ni content of approximately 4% in addition to other alloying elements (N, Mn, C, …) [11].…”

Effect of Aging Temperature on the Microstructure and Properties of Economical Duplex Stainless Steel

“…However, isothermal aging at temperatures in the range 600–1000 °C or inadequate heat treatment leads to the precipitation of secondary phases such as nitrides, σ phases, χ phases, and other intermetallic phases [8,9,10], which will in turn significantly reduce material performance [11]. For example, Straffelini et al [12] investigated the effect of aging treatment on the impact energy of economical duplex stainless steel. Results revealed that soaking samples at 550–850 °C for 5–120 min leads to the observation of precipitated phases at the α/α and α/γ phase boundaries, which decreases the impact energy and brittle fracturing.…”