Defect and Phase Transformation Pathway Engineering for Desired Microstructures: Poster Session
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Yufeng Zheng, University of North Texas; Rongpei Shi, Harbin Institute of Technology; Yipeng Gao, Jilin University; Timofey Frolov, Lawrence Livermore National Laboratory; Stoichko Antonov, National Energy Technology Laboratory; Jessica Krogstad, University of Illinois at Urbana-Champaign; Bin Li, University Of Nevada, Reno
Tuesday 5:30 PM
March 16, 2021
Room: RM 55
Location: TMS2021 Virtual
Anisotropic Thermal Lattice Expansion and Crystallographic Structure of Strontium Aluminide within Al-10Sr Alloy as Measured by In-situ Neutron Diffraction: Klaus-Dieter Liss1; Stefanus Harjo2; Takuro Kawasaki2; Kazuya Aizawa2; Pingguang Xu3; 1Guangdong Technion - Israel Institute of Technology (GTIIT); 2J-PARC Center, Japan Atomic Energy Agency; 3Materials Sciences Research Center, Japan Atomic Energy Agency
Knowledge of thermal evolution of precipitate is essential for microstructural design. The aluminium strontium master alloy Al-10Sr has been investigated by in-situ neutron diffraction upon a heating-cooling cycle, revealing composition, crystallographic structure, lattice evolution and linear thermal expansion coefficients. Expansion of the Al matrix between [23.5 … 26.7]·10‑6 K‑1 fits well to the literature values, extrapolating to higher temperature at 800 K. Thermal expansion is highly anisotropic for tetragonal Al4 Sr by a factor of 1.86 with values of 20.8 and 11.1·10‑6 K‑1 in a and c-axis. The discrepancy to the matrix explains residual intergranular phase stresses and brittleness of such composite material. Upon first heating, recovery is observed until 600 K and 700 K, for Al4 Sr and Al. Rietveld analysis refines the Wyckoff positions of the I 4/m m m crystal structure. Its lattice parameters report to aI = 4.44240(48) Å, cI = 11.0836(15) Å at 300 K.
Deformation Induced Precipitation (DIP): A Cohesive Processing Strategy to Strengthen Magnesium Alloys: Suhas Eswarappa Prameela1; Peng Yi1; Laszlo Kecskes1; Michael Falk1; Timothy Weihs1; 1Johns Hopkins University
Unlike Aluminum alloys, precipitation strengthening of Magnesium alloys has proven challenging. Precipitate density is typically too low, and precipitate size is often too large and elongated to enhance the resistance to plastic deformation significantly. Mimicking recent work in Al alloys, we are exploring how low-temperature plastic deformation can enhance both the density, size, and morphology of common intermetallic particles and thereby lead to significant hardening in Mg alloys. The low temperatures tend to favor nucleation overgrowth, while the deformation provides vacancies and dislocations that can accelerate nucleation. Using varying levels of deformation, and moderate temperatures, we explore the processing and thermodynamic factors controlling nucleation and growth of precipitates in Mg-Al and Mg-Zn binary alloys.
The Effects of Defect Structure on Transformation Properties in NiTi Alloys for Phase Change Thermal Management Applications: Asher Leff1; Adam Wilson1; Darin Sharar1; 1CCDC Army Research Laboratory
Recently we have identified a novel application for the Martensitic transformation undergone by NiTi and related alloys: use as a phase change material (PCM) to absorb and release heat isothermally. PCMs are widely used in order to mitigate thermal spikes in electronics but typically involve a solid-liquid transformation. The reversible solid-solid transformation undergone by NiTi has many advantages and we have demonstrated that commercial NiTi has a figure of merit for this application two orders of magnitude higher than the materials currently in use. Engineering the microstructure of NiTi to optimize its performance in this application space is a unique challenge, however. The critical properties are high latent heat of transformation, minimized transformation temperature hysteresis, and high thermal conductivity, properties heavily connected to the defect structure in both phases. In this study the effect of composition and microstructure on these critical properties is explored.