Phase Transformations and Microstructural Evolution: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Rongpei Shi, Harbin Institute of Technology; Yipeng Gao, Jilin University; Fadi Abdeljawad, Lehigh University; Bharat Gwalani, North Carolina State Universtiy; Qi An, Iowa State University; Eric Lass, University of Tennessee-Knoxville; Huajing Song, Los Alamos National Laboratory

Wednesday 5:30 PM
March 17, 2021
Room: RM 57
Location: TMS2021 Virtual


Dilatometric Analysis of Tempering Kinetics in a Cr–Mo–V Medium Carbon Steel: Eliuth Barrera-Villatoro1; Octavio Vázquez-Gómez1; Alexis Gallegos-Pérez1; Héctor Vergara-Hernández1; Edgar López-Martínez2; Pedro Garnica-González1; 1Tecnológico Nacional de México / I.T. Morelia; 2Universidad del Istmo
    Tempering kinetics of the martensite was determined using the Johnson–Mehl–Avrami model in a Cr–Mo–V alloyed medium carbon steel by dilatometry. The tempering temperatures were determined by non–isothermal analysis at constant heating rate. From these temperatures, isothermal tempering was carried out at different times and the reaction stages were associated with the transformation of retained austenite in bainitic ferrite and cementite, and the conversion of transition carbides and coarsening of cementite. Through dilatometric analysis and the normalization relation the degree of reaction was calculated and it was compared with the degree of transformation estimated with JMA model. Finally, the third tempering stage were related with the kinetic tempering parameters reported in the literature.

Exploring Non-conventional Microstructural Evolution in Titanium Alloys by Advanced Characterization and Machine Learning: Dian Li1; Xing Zhang2; Yiliang Liao2; Yufeng Zheng1; 1University of Nevada, Reno; 2Iowa State University
    Titanium alloys are important structural materials and their balanced properties can be manipulated via microstructural engineering. In order to explore the various novel non-conventional microstructural evolutions in titanium alloys, accurate materials characterization and rapid microstructure analysis are required. In the present work, the microstructural evolution in a beta titanium alloy, Ti-5Al-5Mo-5V-3Cr (wt.%, Ti5553), under different thermomechanical treatments has been characterized using scanning electron microscopy and analyzed using machine learning. The large amount of image data was quantitatively analyzed via the deep learning module in the image analysis software, MIPAR, focusing on the important features of alpha microstructure, e.g., morphology, size and areal fraction. The response of cold-rolled Ti5553 to the subsequent heat treatment was explored via advanced electron microscopy. The factor of mechanical treatment has been taken into consideration for microstructure engineering in Ti5553 and the influence of prior deformation twin on the microstructural evolution in Ti5553 will be introduced.

Thermal and Mechanical Characterization of the Non-isothermal Tempering of an Experimental Medium-carbon Steel: Perla Díaz-Villaseñor1; Octavio Vázquez-Gómez1; Héctor Vergara-Hernández1; Alexis Gallegos-Pérez1; Edgar López-Martínez2; Bernardo Campillo3; 1Tecnológico Nacional de México / I.T. Morelia; 2Universidad del Istmo; 3Universidad Nacional Autónoma de México
    A medium–carbon steel alloyed with vanadium was analyzed by differential dilatometry and nanoindentation tests to characterize the fourth tempering stage or secondary hardening zone. From isochronal heating paths at different continuous tempering temperatures, the hardening zone preceding the martensite decomposition initiation temperature was delimited. A progressive increase in microhardness was observed proportional to continuous tempering temperature increase respect to start temperature of fourth tempering stage at the lowest heating rate. This increase was related to secondary hardening zone by alloy carbides precipitation. Likewise, isothermal tempering was carried out at the start of the fourth tempering stage to verify secondary hardening. After the thermal cycles, nanoindentation tests were performed to determine the nanohardness and prove the precipitates presence by scanning probe microscopy. A decrease in the nanohardness of the steel was observed, as well as different size and distribution precipitates depending on the heating rate.