Displacive Transformations in Non-Metallic Materials: Poster Session
Program Organizers: Mohsen Asle Zaeem, Missouri University of Science and Technology
Monday 5:30 PM
July 10, 2017
Room: Crystal Ballroom A
Location: Hyatt Regency Chicago
P1-12: Influence of Cryogenic Treatment in Thermomechanical Properties in Cu-14Al-4Ni-0.5Ti Alloy: Marcelo Nava1; 1IFBA/UNB
SMA are used in functional elements of sensors and actuators in temperatures close to the ambient temperature. However, with deep cryogenic treatment (DCT), these materials may have their properties potentiated, as to modification of the recovery parameters of the memory effect and the stabilization of phase transformation temperatures. This work was executed DCT for 24 hours at -292 F to check its influence on the thermomechanical properties of SMA alloys Cu-14Al-4Ni-0,5Ti system. The phase transformation temperatures, as well as the latent heats of transformation showed the following values for the untreated alloy was obtained TMs= -4,45 F and TMf= 29,78 F, TAs= 48,47 F and TAf= 29,03 F. For cryogenically treated alloy was obtained TMs= -0,868 F and TMf= 24,36 F , TAs= 43,48 F and TAf= 38,53 F. The hardness of the untreated alloy and cryogenically treated were, respectively, 78.8 ± 1 and 80.1 ± 1.26 HV.
P1-13: Study of Transformation Induced Microcracking in Tetragonal Zirconia Polycrystals with the Phase Field Method: Jun Luo1; Jingming Zhu1; Qiao Ni1; 1Huazhong University of Science and Technology
When tetragonal zirconia polycrystals (TZPs) are exposed to a moisture environment, the tetragonal phase in the surface layer tends to transform to the monoclinic phase, which is usually accompanied with microcracking. This phenomenon,called low temperature degradation (LTD),poses serious issues to the mechanical performance of biomechanical implants made of TZP.In this work, a coupled phase field method is developed to study the transformation induced microcracking in polycrystalline tetragonal zirconia. The micrcracking pattern is successfully predicted with the developed phase field method. The validity of the simulation results is shown by a stress analysis. Our simulation results show that microcracking tends to take place at the grain boundaries where the propagation of martensitic plates with enough thickness is blocked. The developed method can be further applied to study the influence of the other microstructure characters on the LTD behavior of TZP.
P1-14: In-situ Synchrotron High Temperature Phase Transformations in ZrO2 and HfO2: Waltraud Kriven1; Scott McCormack1; Richard Weber2; 1University of Illinois at Urbana-Champaign; 2Materials Development, Inc.
ZrO2 and HfO2 are well known for their martensitic phase transformations from tetragonal to monoclinic with a volume change of (+) 4.9% and (+) 2.99% at 950 ˚C and 1700 ˚C respectively. These martensitic phase transformations have been studied in-situ using the Kriven Group’s Quadrupole Lamp Furnace (QLF) in conjunction with synchrotron radiation, allowing for accurate thermal expansion above and below the martensitic phase transformation. The cubic to tetragonal phase transformation in ZrO2 and HfO2 have also been studied at 2400 ˚C and 2700 ˚C respectively, using the high temperature levitation system in conjunction with synchrotron radiation developed by Richard Weber at Materials Development Inc. These in-situ measurements have shown the cubic to tetragonal phase change to be gradual and having a ~0% volume change at the point of transformation.These two transformations in ZrO2 and HfO2 have been compared in-situ to gain insight into the transformation mechanisms