Phase Transformations and Microstructural Evolution: Non-Ferrous Alloys
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 8:30 AM
March 17, 2021
Room: RM 57
Location: TMS2021 Virtual
Session Chair: Deep Choudhuri, New Mexico Institute of Mining and Technology
8:30 AM
Effect of Zirconium Addition to Wrought Al-Mg-Si Alloys on Microstructure: Florian Schmid1; Irmgard Weißensteiner2; Matheus Tunes2; Thomas Kremmer2; Thomas Ebner3; Peter J. Uggowitzer2; Stefan Pogatscher2; 1Christian Doppler Laboratory for Advanced Aluminum Alloys; 2Montanuniversitaet Leoben; 3AMAG rolling GmbH
In a dynamic environment with ever changing parameters, materials need to be enhanced and adapted constantly. A high maximum strength is crucial for the application of aluminum alloys in demanding environments, like aerospace or heavy machinery, and to compete successfully against other metals. This study aims at spotlighting measures to increase the strength of AlMgSi alloys by changing the chemical composition as well as processing parameters. Besides age-hardenable elements (Si, Mg and Cu), the addition of Zr shows a high potential for its usage as dispersoid forming element. Upon suitable heat treatment parameters, Zr forms Al3Zr-precipitates, which are known to have a high potential for stabilizing the microstructure and act resistively against recrystallization. In order to evaluate the influence of the presented measures, microstructure evolution during thermo-mechanical treatment is examined by electron microscopy. Results are discussed in terms of mechanical parameters, recrystallization tendency and dispersoid density.
8:50 AM
Phase Transitions in Beta Ti and Beta Zr Alloys: Josef Strasky1; Anna Veverková1; 1Charles University
Titanium alloys and zirconium alloys can occur in different crystalline arrangements - phases - depending on the composition and processing of the material. While the phase transformations in titanium alloys have already been, the phase transformations in zirconium are significantly less explored. Zirconium is mainly used in nuclear energy due to its low effective neutron capture cross section. Alloys that contain alloying elements to maintain the beta phase of the material are referred to as metastable beta alloys. Phase transformations in binary Ti-Mo alloys have been studied in detail with the use of in-situ and ex-situ methods. Acquired knowledge was used for the study of Zr-Nb binary alloys.
9:10 AM
Local Phase Transformation Strengthening in Ni-based Superalloys: Ashton Egan1; Timothy Smith2; You Rao1; Longsheng Feng1; Emmanuelle Marquis3; Maryam Ghazisaeidi1; Yunzhi Wang1; Steve Niezgoda1; Michael Mills1; 1Ohio State University; 2NASA Glenn Research Center; 3University of Michigan
In the intermediate temperature creep regime of Ni-based superalloys (~700 °C) deformation is dominated by planar defects and microtwinning, where deformation response is controlled by segregation events surrounding the leading partial dislocations. Of particular interest are alloys exhibiting Local Phase Transformation (LPT) along planar defects, a dynamic process whereby the alloy can be strengthened during service. The propensity for LPT strengthening depends on the relative ratio of η and/or χ formers, depending on active mechanisms, and in this study the LPT composition regime was explored with several commercial and novel alloys. Advanced characterization of the deformation mechanisms and LPT was accomplished by Scanning Transmission Electron Microscopy (STEM), Energy Dispersive X-Ray Spectroscopy (EDS) and Atom Probe Tomography (APT), while being supported by density functional theory (DFT) and phase field computational techniques. Understanding these complex phenomena is crucial in creating a physically-based, constitutive creep model.
9:30 AM
On the Application Potential of Aluminum Crossover Alloys: Lukas Stemper1; Matheus Tunes1; Ramona Tosone2; Peter Uggowitzer1; Stefan Pogatscher1; 1Montanuniversitaet Leoben; 2AMAG rolling GmbH
A major obstacle aluminum alloys are facing is the trade-off between mechanical strength and formability. While most alloys address one of these issues satisfactorily, they hardly meet the requirements of the other. Crossover alloys try to overcome this challenge by merging beneficial properties usually attributed to certain alloy classes into a new single alloy while inhibiting detrimental effects. In this study we present a multi-method characterization of a variety of crossover alloys. After applying a specifically tailored thermomechanical treatment these alloys are not only capable of overcoming the long-standing trade-off between high “in-use” strength and high forming performance during processing but also set new benchmarks in terms of reduced processing time. Mechanical testing, scanning transmission electron microscopy (STEM) and atom probe tomography (ATP) were deployed to disclose the link between microstructural evolution and related material properties, ultimately revealing the mechanisms involved to provide the wide application potential of such alloys.
9:50 AM
Thermal Behavior and Decomposition of Quasicrystalline Dispersoids in Powder-processed Aluminum Alloys: Hannah Leonard1; Sarshad Rommel1; Mingxuan Li1; Thomas Watson2; Tod Policandriotes3; Mark Aindow1; 1University of Connecticut; 2Pratt & Whitney; 3Collins Aerospace
Recently, we have developed a series of Al-Cr-Mn-Co-Zr alloys that exhibit a nano-composite FCC Al plus quasicrystalline I-phase microstructure in gas-atomized powders. The I-phase dispersoids exhibited a variation in microstructures and distribution that depended on the powder particle size (hence cooling rate) and the alloy composition. This microstructure is retained during consolidation of the powder to form bulk materials or cold-sprayed coatings, and the materials exhibit remarkable mechanical properties. Here we report a study on the thermal stability and decomposition of the I-phase and on the microstructural evolution of these alloys. A series of isothermal heat treatments were performed to determine the conditions under which the quasicrystalline phase decomposes. In-situ TEM heating experiments were performed with a MEMS-based heating holder on specimens prepared using a FIB technique from individual powder particles and from consolidated material. Experiments were conducted to investigate the transformation mechanisms for each of the different microstructures.