Mechanical properties of a thermally-aged cast duplex stainless steel by nanoindentation and micropillar compression

Mechanical Properties of a Thermally-aged Cast Duplex Stainless Steel by in Situ Tensile Test at the Service Temperature

“…Regarding the tests at 320 • C, the curves of 2000 h-aged condition present an obvious shift compared with the as received condition, then the curves of the annealed condition drop to almost the same level with the as received condition. Similar phenomenon was also found in the nanoindentation tests [11,14] and micropillar compression of ferrite phase [11]. Many researchers have found that the ferrite phase shows a significant hardening through the formation of spinodal decomposition and the precipitation hardening caused by the G-phases [11,[13][14][15] during long-term thermal aging.…”

“…More information of this steel, such as the three-dimensional (3D) microstructure, can be found elsewhere [5]. The as received material was thermally aged at 475 • C for up to 2000 h, which is essentially equivalent to that of 45 years at the service temperature [11] according to the Arrhenius equation [29]. A part of the 2000 h-aged material was further annealed at 550 • C for 3 h to dissolve the precipitates formed during the thermal aging process [11,13,14].…”

“…One use for CDSS is in coolant water pipes in the pressurized water reactor (PWR) which are designed for at least a 40-year service life and to work in service temperatures ranging from 288 • C to 327 • C [4]. Hence, such pipes experience problems of thermal aging embrittlement during service that cause degradation in mechanical properties [5][6][7][8][9][10][11][12][13][14][15]. It has been reported that the thermal aging embrittlement in CDSS was caused by the precipitation that formed in the ferrite phase after long-term thermal aging, e.g., the G-phase precipitates and the spinodal decomposition during which the ferrite phase decomposes into a Fe-rich α-phase and a Cr-rich α'-phase [10,11,[13][14][15].…”

“…Hence, such pipes experience problems of thermal aging embrittlement during service that cause degradation in mechanical properties [5][6][7][8][9][10][11][12][13][14][15]. It has been reported that the thermal aging embrittlement in CDSS was caused by the precipitation that formed in the ferrite phase after long-term thermal aging, e.g., the G-phase precipitates and the spinodal decomposition during which the ferrite phase decomposes into a Fe-rich α-phase and a Cr-rich α'-phase [10,11,[13][14][15]. Many researchers have found that the mechanical properties of CDSS are strongly dependent on the strength of each individual phase [16,17] and their microstructures, e.g., the volume fraction and the morphology of the ferrite phase, have meaningful influence on the fracture toughness, thermal aging embrittlement, high-temperature ductility, impact properties and corrosion resistance of duplex stainless steel [18][19][20][21][22][23][24].…”

Effect of phase shape and size on the FEM analysis of indentation test of duplex stainless steel microstructures

“…The microstructure of DSS, consisting of austenite and ferrite phase, is successfully modelled in ABAQUS finite element program. Zhang et al [11], were investigated mechanical properties of ferrite and austenite phases in DSS which is thermally aged under 475 °C. They used the nanoindentation test for mechanical properties and showed that the hardness of ferrite continuously increases with increasing aging time.…”