Processing—Microstructure—Property Relationships of Titanium and Titanium Alloys: Session II
Sponsored by: TMS Titanium Committee
Program Organizers: Yufeng Zheng, University of North Texas; Rongpei Shi, Harbin Institute of Technology; Michael Gram, Pratt & Whitney
Wednesday 2:00 PM
October 20, 2021
Room: B246
Location: Greater Columbus Convention Center
Session Chair: Michael Gram, Titanium Metals Corporation; Yufeng Zheng, University of Nevada Reno
2:00 PM
Computational Polarized-Light Microscopy for Microtextured Regions Characterization in Titanium Alloys: Matthew Dahar1; Sesh Tamirisakandala1; Dan Satko2; Ayman Salem2; 1Howmet Aerospace; 2Materials Resources, LLC
Microtextured regions (MTRs) are spatially and crystallographically clustered alpha grains that cause significant debits in fatigue life under cold dwell loading conditions such as those experienced during operation of jet engines. Large-area electron backscatter diffraction (EBSD) is the primary tool to characterize MTRs (size, shape, and crystallographic orientation) but limitations due to sample prep, size, cost, and time restrict implementation. An alternative method for MTRs quantification is based on orientation reconstruction from computational polarized-light microscopy (CPM) data. Using a polarized-light instrument developed by MRL (TiPolarTM), data were recorded at an effective 200,000 pixel per second at 0.4 micrometer resolution (1000x faster than EBSD) without the attendant size and atmosphere limitations typical of EBSD. Data analytics were applied to determine c-axis orientation. Examples of application of CPM to different titanium alloys will be presented to demonstrate the capabilities and robustness of the method with comparisons to EBSD measurements.
2:20 PM
Computational Polarized Light Microscopy for Orientation-based Quality Control: Dan Satko1; Thomas Carmody1; Chasen Ranger1; Sesh Tamirisakandala2; Matthew Dahar2; Ayman Salem1; 1MRL Materials Resources LLC; 2Howmet Aerospace
Heterogenous spatial distribution of alpha phase crystallographic orientation could result in detrimental effects on fatigue life in wrought titanium alloys and large scatter in the properties of additively manufactured components. While EBSD provides accurate data, its utility towards understanding texture heterogeneities at the component scale is limited to smaller areas due to the high cost of measurement and stringent sample requirements. We are presenting an alternative technique based on computational polarized microscopy that can cover 1000s of mm2 with sub-micrometer resolution. Due to the big data generated, quantitative data analytics are discussed with an emphasis on the use of machine learning for establishing orientation-based metrics for quality control. Case studies are presented for wrought alpha/beta titanium and additively manufactured by laser and electron beam powder bed fusion and wire arc additive manufacturing. Automated feature extraction of alpha laths, alpha colonies, alpha grains, and microtextured regions are presented.
2:40 PM
Now On-Demand Only: Strain Energy Density Fatigue Assessment of Ti-6Al-4V for Plain and Notched Geometries
: Jeremy Massie1; Casey Holycross2; Joy Gockel1; 1Wright State University; 2Air Force Research Laboratory
Strain energy density (SED) has previously been shown to predict the life of tensile specimens for more general cases than stress based approaches, as energy models can account for complex loading and stress concentrators. This study investigates the use of SED to model the uniaxial fatigue behavior of Ti-6Al-4V specimens of plain, U-notch and V-notch geometries under fully reversed loading. Tests were completed with a range of 1 (static) to 106 cycles, with a focus between 103 and 106 cycles. Cyclic SED data from all three specimen types are examined, and initial results suggest that cyclic SED models fatigue life of the specimens accurately and in more regimes than a conventional SN curve. The average cyclic SED of plain specimens is modeled to capture LCF and HCF behavior, and multiple methods of calculating the average cyclic SED for notched geometries are explored and discussed.
3:00 PM
Obtaining High Strength-ductility Combination inTIitanium by Microstructure and Texture Engineering through Multiaxial Plane-strain Forging: Devesh Chouhan1; Somjeet Biswas2; 1Indian Institute of Technology KGP; 2IIT KGP
Commercially pure titanium (Ti) is utilised in various automobile industries due to its low density and high corrosion resistance. The advancement in technology and increased design complexity requires high strength- ductility combination in lightweight structural components to improve fuel efficiency. This can be achieved by developing the ultra-fine grain (UFG) structure through a combination of severe plastic deformation (SPD) and conventional processing techniques. In this study, Ti is processed via a novel processing route nomenclature as multiaxial plane-strain forging followed by rolling at ambient temperature. Twin free microstructure with an average grain size of ~100 nm and the multi-component basal texture was obtained. The processed Ti consists highest strength-ductility combination reported in the literature.