Study of Micro Deformation of Austenitic-Ferrite Duplex Stainless Steel by Nanoindentation Method

2016 ◽  
Vol 725 ◽  
pp. 316-321
Author(s):  
Su Juan Guo ◽  
Yuan Yuan Cui ◽  
Fu Zhen Xuan ◽  
Xiao Wang
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Load Level ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Indentation Creep ◽  
Evolution Rule

Based on the technology of the nanoindentation, the basic mechanical properties and cyclic deformation behavior of the austenite phase and ferrite phase in an austenitic-ferritic duplex stainless steel was studied. Firstly, from the displacement monotonic indentation experiment, the differences between the basic mechanical properties (e.g. hardness and elastic modulus) of austenite phase and ferrite phase are compared. Then, with the incremental load controlled loading-unloading conditions applied, the indentation depth evolution rule and the indentation creep behavior was studied. Finally, with the load controlled cyclic indentation experiments being conducted, the cyclic evolution rule of displacement into surface were observed, and the influence of different load level on the micro cyclic deformation behavior of each phase were discussed.

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

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 317 ◽  
Author(s):  
Qingdong Zhang ◽  
Sida Ma ◽  
Tao Jing
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Thermal Aging ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Service Temperature

Z3CN20.09M cast duplex stainless steel (CDSS) has been used for primary coolant water pipes in pressurized water reactors due to its excellent mechanical properties. Such pipes operate at an elevated service temperature (~320 °C) and experience issues of thermal aging embrittlement. In situ tensile tests were conducted to investigate the deformation mechanisms of Z3CN20.09M CDSS after long-term thermal aging at 475 °C for up to 2000 h in both optical microscope and scanning electron microscope at 320 °C. For the 320 °C tests, the tensile stress and other mechanical properties, e.g. the yield stress and the ultimate tensile strength, increase during the thermal aging process and recover to almost the same level as the unaged condition after annealing heat-treatment, which is caused by the formation and dissolution of precipitation during aging and anneal heat-treatment, respectively. For the slip mechanism, straight slip lines form first in the austenite phase. When these slip lines reach the austenite/ferrite interface, three kinds of slip systems are found in the ferrite phase. During the fracture process, the austenite phase is torn apart and the ferrite phase shows a significant elongation. The role of the ferrite phase is to hold the austenite matrix, thus increasing the tensile strength of this steel.

scholarly journals A Comparison of Amplitude-and Time-Dependent Cyclic Deformation Behavior for Fully-Austenite Stainless Steel 316L and Duplex Stainless Steel 2205

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5594
Author(s):  
Shaohua Li ◽  
Wenchun Jiang ◽  
Xuefang Xie ◽  
Zhilong Dong
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Structural Integrity ◽  
Low Cycle Fatigue ◽  
Cyclic Softening ◽  
Plastic Strain Amplitude ◽  
Cyclic Plasticity ◽  
Stainless Steel 316L

Austenite and duplex stainless steels are widely used in engineering, and the latter exhibits a more excellent combination of mechanical properties and corrosion resistance due to the coexistence of austenite and ferrite and higher nitrogen. However, fatigue failure still threatens their structural integrity. A comprehensive comparison of their cyclic deformation behavior is a major foundation to understand the role of duplex-phase microstructure and nitrogen in the safety assessment of engineering components. Thus, in this paper, the cyclic deformation behavior of fully-austenitic stainless steel 316L and duplex stainless steel 2205 was studied by a series of low cycle fatigue tests with various strain amplitudes, loading rates and tensile holding. A theoretical mechanism diagram of the interaction between nitrogen and dislocation movements during cyclic loads was proposed. Results show that the cyclic stress response of 2205 was the primary cyclic hardening, followed by a long-term cyclic softening regardless of strain amplitudes and rates, while an additional secondary hardening was observed for 316L at greater strain amplitudes. Cyclic softening of 2205 was restrained under slower strain rates or tensile holding due to the interaction between nitrogen and dislocations. The cyclic plasticity of 2205 started within the austenite, and gradually translated into the ferrite with the elevation of the cyclic amplitude, which lead to a decreased hardening ratio with the increase in amplitude and a shorter fatigue life for a given smaller plastic strain amplitude.

Microstructure Characterization of Duplex Stainless Steel Welding Joint with Different Solution and Aging Treatment

2010 ◽  
Vol 658 ◽  
pp. 376-379
Author(s):  
Jun Yang ◽  
Tuo Yan Zhang ◽  
Jun Hui Yu ◽  
Wei Zhang ◽  
Jiao Li
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Volume Fraction ◽  
Optical Microscope ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Solution Temperature ◽  
Eutectoid Reaction ◽  
Σ Phase ◽  
Stainless Steel Welding

The microstructural evolutions of 2205 duplex stainless steel welding joints were investigated in this paper. The specimens were solution treated at 1100°C and 1200°C for 1 h, water quenched and then isothermal aged for various durations at 850°C, followed by water cooling. The volume fraction of ferrite phase in HAZ, weld and base metal of the steel were measured by the ferrite scope detector. The changes of microstructure in sigma (σ) phase, ferrite and austenite phase were analyzed by optical microscope and energy dispersive spectrum. The results show that the volume fraction of ferrite phase increases and the ferrite grain becomes coarse when solution temperature enhances from 1100°C to 1200°C. During the aging, σ phase precipitates at γ/δ phase boundary and grows into the ferrite phase, and a eutectoid reaction of δ→σ+γ2 occurs. With extending of the aging time, the amount of ferrite phase decreases, σ phase increases and thin needle secondary austenite phase distributes across ferrite grains. In addition, high solution temperatures can delay the procedure of σ phase precipitation.

Structure and mechanical properties of laser-MIG hybrid welded SAF 2507 super duplex stainless steel joints

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940037 ◽  
Author(s):  
Kai Qi ◽  
Ruifeng Li ◽  
Guangjin Wang ◽  
Zhe Sun
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Weld Metal ◽  
Duplex Stainless Steel ◽  
Phase Distribution ◽  
Welding Process ◽  
Austenite Phase ◽  
Welding Parameters ◽  
Super Duplex Stainless Steel ◽  
Phase Balance

Joining of super duplex stainless steel (SDSS) is still a challenge, in particular, the need to control the phase balance in the weld metal. In this paper, laser-MIG hybrid welding process was used to join SAF 2507 SDSS plates. The effects of welding parameters on weld appearance, microstructure and phase distribution and mechanical properties were studied systematically. Results showed that the arc/laser hybrid effect was more significant when the arc led the laser with 2 mm distance. It was indicated that arc current mainly affected the weld width while laser power mainly affected weld penetration depth. The composition and microstructure varied a lot at different positions in the weld due to the differences in peak temperature and cooling rate. From top to root, the content of ferrite phase increased and austenite phase decreased. With optimized welding parameters, due to the increase of heat input and the introduction of welding wire, the ferrite/austenite phase balance in the weld metal was obtained. Mechanical property tests showed that the joints exhibited higher tensile strength but lower toughness compared to base metal.

A Comparative Study on the Cyclic Behavior of Austenite/Ferrite Phases Characterized by the Nanoindentation

2016 ◽  
Vol 853 ◽  
pp. 137-141
Author(s):  
Yuan Yuan Cui ◽  
Yun Fei Jia ◽  
Fu Zhen Xuan
Keyword(s):  
Stainless Steel ◽  
Penetration Depth ◽  
Deformation Behavior ◽  
Transient State ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Cyclic Behavior ◽  
Quasi Steady State ◽  
Maximum Penetration Depth ◽  
Maximum Penetration

The cyclic deformation behavior of the austenite and ferrite phase in an austenite-ferrite duplex stainless steel was studied by using the load-controlled cyclic nanoindentation approach. The results showed that the maximum penetration depth onto both austenite and ferrite phases increased continuously while the rate decreased gradually and finally reached to a constant during the repeated indentation. Both transient state and quasi-steady state were observed for the penetration depth per cycle on both of the austenite and ferrite phases with the increased cycles. By contrast, both the penetration depth and rate per cycle into the austenite phase were larger than those into the ferrite phase. This was ascribed to the stress-induced densification in the austenite and ferrite phases and strain-induced transformed martensite in the austenite phase.

Sign in / Sign up

Export Citation Format

Share Document