4th International Congress on 3D Materials Science (3DMS) 2018: Corrosion and Fracture I
Program Organizers: Hugh Simons, Denmark Technical University; Henning Poulsen, Denmark Technical University; David Rowenhorst, Naval Research Laboratory; Peter Voorhees, Northwestern University; Satoshi Hata, Kyushu Univ; McLean Echlin, UC Santa Barbara
Monday 3:50 PM
June 11, 2018
Room: Lille Scene
Location: Kulturværftet (Culture Yard) Conference Center
4D Non-destructive Investigations of the Influence of Crystallographic Orientation and Microstructure on Corrosion in Aluminum Alloys: Tyler Stannard1; Sridhar Niverty1; Jacob Graber1; Jason Williams1; Hrishikesh Bale2; Nicolas Gueninchault3; Nikhilesh Chawla1; 1Arizona State University; 2Carl Zeiss Microscopy Inc.; 3Xnovo Technology ApS
Aluminum alloys used extensively in aircraft components and skins are frequently exposed to harsh environments; corrosive saltwater spray combined with the fatigue stresses of flight operations in service. Several factors including the underlying microstructure, defects, and crystallographic grain orientation play a dominant role in corrosion-related fracture of these alloys. Grain mapping techniques like EBSD are restricted to 2D surface imaging and can only be extended in 3D through destructive sectioning. Laboratory-based diffraction contrast tomography (LabDCT) is possible on a commercially available X-ray microscope, enabling time-dependent ‘4D’ corrosion studies, wherein samples can be imaged in 3D at high resolution to understand the complex mechanisms of corrosion. Here, we present experimental results acquired on aluminum 7475 using LabDCT that investigate corrosion behavior of these alloys. Further examination of the influence of inclusions, triple point grain boundaries and misorientation on the corrosion evolution based on the 3D data analysis will also be discussed.
Understanding Environmentally Assisted Cracking of High Strength Aluminium Using In Situ X-ray CT: Tim Burnett1; Henry Holroyd2; John Lewandowski3; Malte Storm4; Philip Withers1; 1Univ of Manchester; 2Consultant; 3Case Western Reserve University; 4Diamond Light Source
Environmentally assisted cracking of high strength aluminium has been the subject of research effort for over 50 years and yet it is still poorly understood. Slow strain rate tests have been conducted in situ on high strength aluminium combined with synchrotron X-ray CT. The growth and morphology of the cracks has been investigated and quantified. The failed specimens were then studied using SEM fractography linking many aspects of the microstructure to the crack morphology. We will present the new insights into the initiation and propagation of these environmentally assisted cracks.
Crack Morphology in a Columnar Thermal Barrier Coating System: Anne Dennstedt1; Fabrice Gaslain1; Marion Bartsch2; Vincent Guipont1; Vincent Maurel1; 1Centre des Matériaux - Mines Paristech - CNRS UMR 7633; 2German Aerospace Center (DLR)
Ceramic layers are used as thermal barrier coatings (TBCs) on metallic substrates. During thermal transients, the thermal expansion mismatch between coating and substrate drives failure of the TBC mainly by interfacial cracking. Laser Shock Adhesion Test (LASAT) provides stresses at the ceramic/metal interface enabling controlled interfacial cracking. For achieving a clear understanding of the influence of local morphology on interfacial toughness, this study aims at characterizing the 3D morphology of a crack at the interface between metal and an EB-PVD TBC having a columnar structure. Cracks were produced by LASAT and documented further in SE and BSE image stacks collected simultaneously during subsequent slice and view operations using a focus ion beam (FIB) and a scanning electron microscope (FIB slice & view). The segmented 3D data gives clear understanding of the columnar structure of the ceramic and of the interaction between the crack and the TBC microstructure.
3D Characterisation of Iodine-induced Stress Corrosion Cracks in Zirconium Alloys: Alistair Garner1; Conor Gillen1; Philipp Frankel1; 1University of Manchester
X-ray computed tomography is used to map the locations and morphology of iodine-induced stress corrosion cracks in zirconium alloys, generated by stressing C-ring samples in iodine-ethanol solution. The presence of iodine is identified using nanoscale secondary ion mass spectrometry and a crack tip region is lifted out for serial sectioning analysis using a Xe plasma focused ion beam (PFIB). Due to high milling rates in the PFIB, a relatively large volume can be analysed with complementary acquisition of both chemical and crystallographic information. The 3D orientation information is correlated to the 3D crack path reconstructed from electron images. Attacked grain boundaries (GBs) are identified from the aligned datasets, from which the GB plane is estimated by fitting a plane to the neighbouring grains surface mesh. This allows for a large number of I-SCC susceptible GBs to be fully characterised and leads to new insight into crack propagation mechanisms.
Topological Characteristics of Three-dimensional Grain Boundary Networks and Their Influence on Stress Corrosion Crack Propagation: Tingguang Liu1; Shuang Xia2; Bangxin Zhou2; Yonghao Lu1; Tetsuo Shoji3; 1University of Science and Technology Beijing; 2Shanghai University; 3Tohoku University
Microstructures of 316L stainless steel before and after grain boundary (GB) engineering have been studied by using serial sectioning coupled with EBSD mapping in terms of 3D characterization. The twin boundary arrangement in the conventional and GB engineered GB networks were investigated and compared. Additionally, an intergranular crack and the GB network along the crack in the conventional 316L after stress corrosion cracking (SCC) test in high-temperature water were investigated in 3D. It was found that the proportions of triple junctions with two twin boundaries and quadruple junctions with three twin boundaries have a considerable increase after GB engineering. The twin boundaries not only show a strong resistance to cracking, but they could also prevent their neighboring boundaries from cracking, as the cracking probability is lower for boundaries that have higher fraction of neighboring twin boundaries.
Development of a Micro-single Edge Notched Tensile (Micro-SENT) Testing to Determine Toughness Using X-ray Synchrotron Tomography: Yazid Madi1; Loic Courtois2; Joseph Marae-Djouda3; Clement Soret4; Maxime Pellerin5; Jacques Besson5; 1EPF-Ecole d'ingénieurs / Centre des Matériaux Mines ParisTech; 23Dmagination Ltd; 3EPF Ecole d'ingénieur-e-s; 4ENGIE Lab - CRIGEN; 5Mines ParisTech, PSL Research University, MAT-Centre des Materiaux
The toughness of a ductile steel used in the pipeline industry is investigated using both standard Single Edge Notched Tensile (SENT) specimen and a developed micro-SENT specimen. Micro-SENT sample is tested using in-situ X-ray synchrotron-radiation computed tomography (SRCT). As a first step, the notch is electro-discharge machined, in order to analyse local mechanical behaviour and damage of the small specimen compared to the conventional one. The SRCT high resolution technique is used to provide clear images to analyse quantitatively the damage evolution during both crack initiation and crack propagation. Indeed, the crack advance is directly measured during propagation and a J-da resistance curve is determined. Digital Image Correlation and Finite Element Analysis are also used to analyse the strain fields around the crack tip.
In-Situ Synchrotron X-ray Micro-tomography of Microstructure Evolution during Ceramic Matrix Composite Processing: Natalie Larson1; Harold Barnard2; Dilworth Parkinson2; Alastair MacDowell2; Charlene Cuellar3; Richard Sim4; Frank Zok1; 1University of California, Santa Barbara; 2Lawrence Berkeley National Laboratory; 3University of California, San Diego; 4University of California, Berkeley
In-situ synchrotron x-ray computed micro-tomography at the Advanced Light Source has been used to observe microstructure evolution during ceramic matrix composite processing. In one set of experiments, impregnation of a liquid matrix precursor into a fiber preform was imaged in-situ. The resulting 4D datasets (1µm3 resolution, 1.5 min sequential scans) reveal fiber movement and void formation over time for a wide range of impregnation speeds. In another set of experiments, polymer-to-ceramic conversion of a preceramic polymer matrix in a SiC fiber preform was imaged in-situ at temperatures up to 1200°C. The resulting 4D datasets (1µm3 resolution, 12 min sequential scans) reveal the spatial and temporal evolution of a complex hierarchy of shrinkage cracks. A quantitative assessment of the microstructure evolution during processing will be presented for both experiments. Additionally, recent developments in the techniques and instrumentation for these and future in-situ processing experiments will be discussed.