Engineered Phase Transformations: Engineered Phase Transformations
Sponsored by: TMS Phase Transformations Committee
Program Organizers: Eric Lass, University of Tennessee-Knoxville; Niyanth Sridharan, Oak Ridge National Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; Bij-Na Kim
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 34
Location: MS&T Virtual
Session Chair: Eric Lass, University of Tennessee, Knoxville
8:00 AM
Phase Fraction Measurements in Textured Materials: Adam Creuziger1; Michael Cox2; Kip Findley2; Thomas Gnaupel-Herold1; Whitney Poling1; Chris Calhoun1; 1National Institute of Standards and Technology; 2Colorado School of Mines, Metalllurgical and Materials Engineering Department
Many advanced high-strength steels rely on metastable austenite phase for improvements in strength and formability. Accounting for crystallographic texture in phase fraction measurements remains a challenge to current standards and practices. Several techniques have been proposed to provide accurate austenite phase fraction measurements in textured materials, such as averaging the intensity of several peaks and/or summation of intensity from several sample orientations. This presentation will show the results of a series of numerical experiments that sought to quantify the effects of texture on the measurement of the austenite phase fraction, with an emphasis on techniques suitable for laboratory X-ray diffraction. The resulting phase fraction calculations showed that texture, the number of peak pairs and the sampling method have a drastic effect on phase fraction measurements, causing significant bias errors. Hexagonal grids produced minimal bias errors and demonstrated a robust method of measuring phase fractions in textured materials.
8:20 AM
Microstructure Engineering in Metastable Beta Titanium Alloy: Stoichko Antonov1; Zachary Kloenne2; Xing Zhang3; Dian Li3; Yiliang Liao3; Hamish Fraser2; Yufeng Zheng3; 1Max-Planck-Institut für Eisenforschung; 2Ohio State University; 3University of Nevada, Reno
The microstructure of metastable beta titanium alloys is so sensitive to thermal and/or mechanical treatment that the mechanical performance of metastable beta titanium alloys can be manipulated by the microstructure engineering, especially via the tuning of hcp alpha precipitates in a matrix of bcc beta phase. Our previous study in Ti-5Al-5Mo-5V-3Cr (wt%, Ti5553) has shown that alpha microstructure of three different size scales, namely refined, more-refined and super-refined alpha, can be generated via the selection of different heat treatment conditions. In this work, the factor of mechanical treatment has been taken into consideration for microstructure engineering in Ti5553. For the first time, novel {10 9 3}<331> deformation twin was observed in the cold-rolled Ti5553. The response of cold-rolled Ti5553 to the subsequent heat treatment was explored via advanced electron microscopy. The influence of deformation twin and pre-formed omega phase on the microstructural evolution will be discussed in detail.
8:40 AM
Grain Size-effect on the Survivability of Shape Memory Zirconia during Cyclic Martensitic Transformations: Isabel Crystal1; Christopher Schuh1; 1Massachusetts Institute of Technology
Shape memory ceramics (SMCs) can crack as they undergo their martensitic transformation from the tetragonal to the monoclinic phase, especially in bulk sample sizes and polycrystalline structures that enhance mismatch stresses. Polycrystalline samples can crack intergranularly and bodily lose grains during cyclic martensitic transformations, and here we explore such degradation as a function of grain size over a range from 0.6 to 7.9 µm for a pellet of a fixed diameter of ~5 mm. Smaller grain sizes are found to slow the rate of disaggregation of the pellet, an effect which we analyze by performing quantitative calorimetry. When such calorimetry analysis is conducted over a large number of transformation cycles, it permits an assessment of the evolution of heat flow as the pellets degrade into a granular packing of loose grains.