Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys: Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys
Program Organizers: Erwin Povoden-Karadeniz, CDL-IPE TU Wien; Ernst Kozeschnik, Vienna University of Technology
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 35
Location: MS&T Virtual
Funding support provided by: MatCalc Engineering GmbH, Vienna
Session Chair: Erwin Povoden-Karadeniz, TU Wien
8:00 AM
Introductory Comments: Thermodynamic Properties, Structure and Phase Stabilities of Special Alloys: Erwin Povoden-Karadeniz1; 1TU Wien CDL-IPE
Introductory Comments
8:05 AM Cancelled
Development of High-performance Al-Ce-Based Alloys: Aurelien Perron1; Emily Moore1; Joel Berry1; Zachary Sims2; Hunter Henderson2; Orlando Rios2; David Weiss3; Scott McCall1; 1Lawrence Livermore National Laboratory; 2Oak Ridge National Laboratory; 3Eck Industries
Recently developed Al-Ce alloys offer a number of beneficial attributes, including high temperature strength retention and resistance to microstructural coarsening. However, further alloying additions to improve properties cannot be designed easily due to complex interactions in multicomponent systems and the vast phase-space to be explored. A Materials Design Simulator (MDS) – based on coupling a CALPHAD thermodynamic software with a global constrained search engine – will be presented to design new Al-Ce-X (X = Cu,Fe,La,Mg,Ni,Si,Zn,Zr) alloys with optimal composition for microstructural control during casting or additive manufacturing. Results for complex alloys with some experimental validations will be presented, and prospects of additional developments for improving the search for high-performance materials will be discussed.Prepared by LLNL under Contract DE-AC52-07NA27344 and supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. DOE, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.
8:35 AM
Deformation Induced Precipitation in Microalloyed Al-Cu: Roman Schuster1; Tomasz Wojcik1; Erwin Povoden-Karadeniz1; 1Christian Doppler Laboratory for Interfaces and Precipitation Engineering (CDL-IPE), Institute of Materials Science and Technology, TU Wien
Alloying aluminum with Cu leads to an enhancement of mechanical properties compared to pure aluminum through the formation of intermetallic precipitates during aging treatment. To minimize costs, a reduced Cu concentration compared to 4 wt% in the 2000 alloy series, while still retaining enhanced mechanical strength, may be preferred for many applications. In this communication we report on the precipitation of CuAl2 θ from a solid solution with less than 1 wt% Cu through processing involving severe plastic deformation. Deformation by high pressure torsion at room temperature and 150°C leads to ultra-fine grained microstructures with grain sizes well below 500 nm at room temperature and about 500 nm at 150°C. TEM analysis reveals the formation of 10-40 nm sized CuAl2 θ precipitates at triple points and Cu enrichment at grain boundaries. Furthermore, the grain interiors exhibit a heterogeneous Cu distribution in the nano-scale showing lamellar regions with enhanced Cu concentration.
8:55 AM
Thermal Decomposition of Quasicrystals in Powder-processed Icosahedral-Phase-strengthened 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 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 in this Al alloy. 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.
9:15 AM
Thermodynamic Properties of Special Alloys of the Ti-Al System Formed under SHS Conditions: Borys Sereda1; Dmytro Sereda1; Yuriy Belokon2; Irina Kruglyak2; 1Dneprovsky State Technical University; 2ZNU
The results of a thermodynamic analysis of the reactions that are possible in the preparation of titanium-aluminum alloy intermetallic compounds under conditions of self-propagating high-temperature synthesis (SHS) are presented. Thermodynamic analysis showed that the adiabatic combustion temperature for the titanium-aluminum system is lower than the melting temperature of the final product, which is an insufficient condition for the SHS reaction to occur under normal conditions. To carry out the synthesis reaction, coarse heating of the system to the a-TiAl temperature of alloys of 400 ... 600 K is necessary. A sequence of SHS reactions is also established, leading to the formation, which helps to elucidate the mechanism of obtaining special alloys of the Ti-Al system formed under SHS conditions.
9:35 AM
Interdiffusion in Ternary Ti-Al-Mo System and Its Application during Homogenization Treatment: Gyanendra Chauhan1; Kaustubh Kulkarni1; 1Indian Institute of Technology Kanpur
Interdiffusion study of ternary Ti-Al-Mo alloys, a subset of many important beta-Ti alloys is important for diffusional behavior understanding of Ti-Al-Mo based alloys and in development of cost-effective manufacturing routes for mass production. In this study, interdiffusion coefficients are evaluated over a larger composition range of beta phase field of ternary Ti-Al-Mo system. 11 independent diffusion couples are annealed for 48hr at 1100°C. Experimental concentration profiles of diffusion structures, evaluated from EPMA-WDS are fitted and are analyzed for interdiffusion fluxes. Interdiffusion coefficients are calculated at 32 intersection points among diffusion paths. These calculated interdiffusivities are correlated with composition by empirical fitting. Using finite difference method based on F.T.C.S. scheme, the diffusion profiles are generated using empirically fitted composition dependent diffusion-data. Validity of evaluated diffusion-data is tested using multi-layered assembly of binary Ti-Al and Ti-Mo alloys, which are diffusion annealed for different duration analogous to dendrites homogenization, important for industrial heat-treatment.
9:55 AM
Examining the Oxidation in NiAl Binary Alloys Using Cellular Automata: Indranil Roy1; Pratik Ray2; Ganesh Balasubramanian1; 1Lehigh University; 2IIT Roper
The atomistic approaches to modeling oxidation on metallic surfaces are limited in the scale of systems they are able to model, while macroscopic and kinetic methods do not account for the nanoscale effects. A mesoscale technique such as cellular automata (CA) bridges that gap, and holds potential to describe surface oxidation phenomena that is comparable to experimental observations. Here we present results from our implementation of the 2-dimensional (2D) CA method based on a stochastic approach to examine the oxidation of equiatomic nickel-aluminum (NiAl) alloy. A rapid increase in metal oxide formation followed by gradual decrease in the oxidation rate implies that the reaction becomes progressively slower with time as a primary layer of oxide forms on the surface. Further, we generate the stress field create solely due to oxidation and discuss the advantage of the CA approach in the context of complementary experimental findings.
10:15 AM Invited
Thermodynamic Modeling of the Ga-Mn-Ni System for Heusler Alloy Development: Liangyan Hao1; Jakub Toman1; Markus Chmielus1; Wei Xiong1; 1University of Pittsburgh
The Ni-Mn-Ga Heusler alloys are important functional materials because of the shape-memory and magnetocaloric effects, and thus often used in actuators and refrigerants. This work applies the CALPHAD (CALculation of PHAse Diagrams) approach with the new generation of lattice stability to describe the thermodynamics of the Ga-Mn-Ni system supported by experiments and ab initio calculations. Experiments are performed to address the existing contradictories in the Ga-Mn system. The DFT method is applied to calculate the enthalpy of formation of Ga-Mn intermetallic compounds. The thermodynamic parameters of the Ni-Mn-Ga system are obtained by extrapolation from the three binary subsystems. This work will facilitate the composition and processing designs of novel Heusler alloys with desired properties.