Environmentally Assisted Cracking: Theory and Practice: Corrosion and Fracture in Harsh Environments
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Bai Cui, University of Nebraska Lincoln; Raul Rebak, GE Global Research; Srujan Rokkam, Advanced Cooling Technologies, Inc.; Jenifer Locke, Ohio State University
Thursday 2:00 PM
February 27, 2020
Room: Theater A-10
Location: San Diego Convention Ctr
Session Chair: Jia Chen, Virginia Tech
2:00 PM Cancelled
Comparative Assessment of the Fracture Behaviour of API-5L X65 and Micro-alloyed Steels in E80 Simulated Fuel Ethanol Environment: Olufunmilayo Joseph1; Seetharaman Sivaprasad2; Soumitro Tarafder2; John Ade Ajayi3; 1Covenant University; 2CSIR-National Metallurgical Laboratory; 3Federal University of Technology, Akure
Monotonic J-integral tests have been conducted for API-5L X65 steel and micro-alloyed steel (MAS) in E80 simulated fuel grade ethanol (SFGE) environment using three-point bend specimens. Loading was carried out very slowly at the ramp rate of 10-04 mm/s in each sequence in order to enhance SCC effect if any. The effect of the SFGE environment on fracture toughness and tearing resistance of the steels was studied. Both steels exhibited decrease in fracture toughness in E80 with respect to air. The decrease in fracture toughness may be due to anodic dissolution at the crack tip. Ductile tearing resistance of the steels increased in E80 due to decline in toughness property. In comparison to X65 steel, MAS showed better fracture properties.
2:20 PM
Effects of Chromium and Molybdenum on Hydrogen Absorption Behavior in Iron: Vanadia Yussalla1; Kenichi Takai1; Tomohiko Omura2; 1Sophia University; 2Nippon Steel Corporation
Effects of chromium (Cr) and molybdenum (Mo) on hydrogen absorption behavior in iron (Fe) have been investigated by determining the equilibrium concentration of hydrogen (CH) and calculating heat of solution of hydrogen (ΔH) in pure Fe, Fe-2.37Cr, and Fe-4.23Mo. Specimens were chemically polished prior to cathodic hydrogen charging. They were charged with hydrogen in solution of 0.1 N NaOH and 5 g/l NH4SCN at 30°C with different charging times to determine CH. To calculate ΔH, they were charged with hydrogen at various temperatures. As results, CH in pure Fe was the highest, whereas that in Fe-4.23Mo was the lowest. It was also found that ΔH of Fe-4.23Mo was the highest. Moreover, pure Fe specimen applied strain of 0.3 has higher negative value of ΔH than pure Fe. These findings indicate that solid solution of Mo in Fe decreases CH compared with that of Cr.
2:40 PM Cancelled
Evidence of Vacancy Generation During Grain Boundary Corrosion of Steel: Denizhan Yavas1; Thanh Phan1; Liming Xiong1; Kurt Hebert1; Ashraf Bastawros1; 1Iowa State University
The mechanical degradation during the corrosion process of low-alloy pipeline steel is explore by nanoindentation measurements and molecular dynamics simulations near the grain boundary, at conditions of high susceptibility to stress corrosion cracking. Nanoindentation measurements show local softening near corroded grain boundaries, indicated by significantly reduced critical loads for dislocation nucleation. Molecular dynamics simulations of nanoindentation of bulk iron showed that metal vacancies and not interstitial hydrogen atoms explain the observed critical load reduction. The vacancies are likely originating from the oxidation of reactive Si solute atoms. These findings provide a plausible link of chemical mechanisms responsible for the formation of vacancies that contribute to the grain boundary degradation.
3:00 PM
Predicting the Tribocorrosion Behavior of Aluminum Alloys Using Finite Element Based Multiphysics Modeling: Kaiwen Wang1; Wenjun Cai1; 1Virginia Polytechnic Institute and State University
The design of robust and reliable metals that are simultaneously wear and corrosion resistance is crucial for various applications where high mechanical stress and corrosive environment coexist. Past research mainly relies on costly and trial-and-error experimental methods for alloy design and optimization. In this work, using finite element analysis (FEA) method, a model was developed to investigate and predict the tribocorrosion properties of aluminum alloys using experimentally obtained mechanical and corrosion properties as inputs. The stress-corrosion synergy effects was modeled based on Gutman’s theory which correlates equilibrium corrosion potential with deformation. The model predicted how the electrochemical and mechanical properties of the material could affect the corrosion rate when the sample is under compressive force. The simulated results provided further insights toward the tribocorrosion-resistant alloy design, suggesting that optimizing mechanical properties like elastic modulus and yield strength could also lower corrosion rate when the material undergoes deformation.
3:20 PM Break
3:40 PM
Investigation of Laboratory versus In-service Sensitization Effects on Corrosion Fatigue Performance of AA5456-H116: Allison Akman1; David Schrock1; Jenifer (Warner) Locke1; 1The Ohio State University
AA5xxx alloys are utilized in marine applications, but corrosion resistance and environment assisted cracking properties can be degraded by the precipitation of anodic β-phase (Al3Mg2) along grain boundaries (sensitization) during in-service thermal exposure. This research aims to understand corrosion fatigue (CF) performance by comparing laboratory and in-service sensitized AA5456-H116 microstructures at three sensitization levels (DoS). Crack growth rates (da/dN) will be compared over a range of stress intensity ranges (ΔK), stress ratios (R), and fatigue loading frequencies. For the same ΔK and R, CF testing of T-L oriented fracture mechanics samples shows that laboratory sensitized microstructures exhibit a higher da/dN than those sensitized in-service at the same DoS. Quantification of grain boundary β-phase coverage and degree of recrystallization via SEM will attempt to correlate microstructural changes with da/dN differences. Gallium-embrittled intergranular fracture surfaces reveal particles covering a highly sensitized microstructure, whereas a low DoS has little to no particles present.
4:00 PM
Phase Field Modeling of Galvanic Corrosion in Magnesium-aluminum Joints: Kübra Karayağiz1; Adam Powell1; Qingli Ding1; Brajendra Mishra1; 1Worcester Polytechnic Institute
Several future light-weight automotive designs require joining aluminum and magnesium alloy parts in order to take maximum advantage of the best properties of both materials. However, such joints inherently give rise to galvanic corrosion between the two metals, their intermetallic compounds, and other phases in the alloys themselves. Presented here is a formulation with two-dimensional results for multiscale modeling of this corrosion, consisting of macroscopic computation of galvanic potential distribution over the joint, coupled with grain-level phase field modeling of micro-galvanic material degradation at each phase. Modeling is guided by experimental observations of aqueous corrosion of diffusion-bonded magnesium-aluminum couples in order to provide a relatively simple geometry and microstructure for initial development. The formulation is intended for later use with more complex geometries and joints including friction stir welds between magnesium and aluminum alloy sheet.
4:20 PM Cancelled
Microstructural Aspects of Hydrogen Induced Stress Cracking in Various Carbon Steel Welds: Hanji Park1; Cheolho Park2; Myeonghyun Kim1; Yangdo Kim1; Namhyun Kang1; 1Pusan National University; 2Korea Atomic Energy Research Institute
Many studies have investigated the hydrogen induced stress cracking (HISC) properties of base metal (BM), fusion zone (FZ), and heat affected zone (HAZ), respectively. However, it is important to evaluate the HISC behaviour of the entire weldments because the actual weldments are applied with stress simultaneously during service. This study aims to investigate the role of the interaction of hydrogen and microstructures on the HISC for transverse welds containing BM, FZ, and HAZ. In-situ slow-strain-rate-testing (SSRT) with hydrogen charging was conducted for YS 360MPa and YS 550MPa grade steel welds. The in-situ SSRT changed the fracture location from BM to HAZ for the transverse weldments. We investigated the hydrogen trapping site in HAZ and initiation-propagation of HISC for various steels. Although some weld microstructures or softened HAZ are harmless under normal conditions in air, they should be critically investigated in a hydrogen atmosphere.