Aluminum Alloys, Processing and Characterization: Microstructure Evolution and Characterization
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Dimitry Sediako, University of British Columbia
Wednesday 8:30 AM
March 17, 2021
Room: RM 27
Location: TMS2021 Virtual
Session Chair: Izabela Szlufarska, University of Wisconsin–Madison
8:30 AM Invited
Microstructure Evolution of an Al-Fe-Ni Alloy with Zr and Sc Additions Upon Different Cooling Rates during Solidification for Improving the Mechanical and Electrical Conductivity Properties: Suwaree Chankitmunkong1; Dmitry Eskin2; Chaowalit Limmaneevichitr1; 1King Mongkut's University of Technology Thonburi; 2Brunel University London
Al-Fe-Ni eutectic alloys have high potential to replace conventional low-conductivity Al casting alloys for various electronic and electrical applications. Furthermore, the addition of Zr and Sc up to 0.3 wt% improves hardness and thermal stability for higher temperature applications, which is a result of the fine Al-Fe-Ni eutectic structure and precipitation hardening by Al3Zr and/or Al3Sc nanoprecipitates. Thus, the aim of this study was to analyze the microstructure changes in an Al-1.75 wt% Fe-1.25 wt% Ni eutectic alloy with Zr and Sc additions upon different cooling rates during solidification. The morphology and dimensions of Al-Fe-Ni eutectics, constitutive intermetallics and eutectic grains were examined in relation to the cooling rate. Mechanical properties and electrical conductivity were examined and correlated to the structure changes.
8:50 AM
Microstructure and Mechanical Properties of a Precipitation-hardened Al-Mn-Zr-Er Alloy: Amir Farkoosh1; David Seidman1; David Dunand1; 1Northwestern University
Commercial aluminum alloys are unusable above ~250 °C (523 K, which is 56% of the absolute melting point of aluminum, Tm = 933 K), due mainly to the rapid coarsening/dissolution of their fine strengthening precipitates. The recently developed L12-strengthened alloys, however, exhibit a significantly better coarsening resistance at high temperatures. In this study, we present a new class of L12-strengthed aluminum alloys based on the Al-Zr-Mn-RE (RE= Rare-Earth elements) system, which exhibits an exceptional combination of high creep and high coarsening resistance in the temperature range 300-400 °C. The microstructure of the alloys in the as-cast and aged conditions has been studied over relevant length scales utilizing scanning electron microscopy (SEM), transmission electron microscopy (TEM), and local-electrode atom-probe (LEAP) tomography in parallel with electrical conductivity and microhardness measurements. Compressive creep experiments are performed to determine the creep threshold stresses of these alloys at 300 and 400 °C.
9:10 AM
Characterization of the Microstructure of Al-Mg Alloy Matrix Syntactic Foam by Three-dimensional Analysis: Jeki Jung1; Su-Hyeon Kim1; Won-Kyoung Kim1; Cha-Yong Lim1; Yong Ho Park2; 1Korea Institute of Materials Science; 2Pusan National University/Department of Materials Science and Engineering
Aluminum alloy matrix syntactic foams are classified as composite foams, and they can be useful for energy-absorber. The mechanical properties of the aluminum alloy matrix syntactic foams are enhanced by the addition of hollow particles, and they have low density and improved energy absorption efficiency. Quantitative analysis of dispersion for the hollow particles in the aluminum alloy matrix syntactic foam is important because the dispersion of the hollow particles is a variable influencing the mechanical properties and deformation behavior. The three-dimensional analysis of the dispersion for the hollow particles can be estimated more clearly than two-dimensional analysis. In this study, we could synthesize the aluminum-magnesium alloy matrix syntactic foams with well-dispersed cenospheres by stir casting, and the microstructure of the syntactic foams are characterized by three-dimensional analysis. Also, we have attempted to quantitatively analyze the distribution and dispersion of the hollow particles in the matrix.
9:30 AM
Thermal Analysis of the Solidification Behavior of AA7075 Containing Nanoparticles: Maximilian Sokoluk1; Igor De Rosa1; Shuaihang Pan1; Xiaochun Li1; 1University of California Los Angeles
The use of high strength, lightweight aluminum alloys in high-tech applications such as aerospace, as well as in the emerging field of electric vehicles, is an integral part of our society’s push towards high energy efficiency. However, solidification processing of such alloys, especially fusion welding and additive manufacturing remains challenging due to solute segregations and ultimately solidification cracking. Recently the use of refractory nanoparticles in hot crack susceptible aluminum alloys showed great potential to mitigate cracking during solidification. This work investigates the solidification mechanisms for aluminum alloy (AA) 7075 treated with a low volume fraction of nanoparticles. Using Differential Scanning Calorimetry (DSC) we showed a significant deviation in solidification behavior of nano-treated alloys from their commercial counterparts.
9:50 AM
Microstructural Evolution of Ultra-fine Grained (UFGs) Aluminum in Tribological Contacts: Shuguang Wei1; Chaiyapat Tangpatjaroen1; Hongliang Zhang1; Izabela Szlufarska1; 1University of Wisconsin Madison
Grain refinement is a promising strategy for improving wear resistance of metals, but in Al previous studies have often shown undesirable wear-induced grain growth. Here, we investigated tribological properties and microstructural evolution during sliding of ultra-fine grain (UFG) aluminum prepared by accumulative rolling bonding and by physical vapor deposition (PVD). The wear-induced grain refinement was observed for the first time in UFG Al and we have identified a transition from grain growth to grain refinement as a function of the mean contact stress. According to the observations from transmission electron microscopy, the mechanism underlying the microstructural evolution is the dynamic recrystallization. We have also found that the PVD-grown UFG Al was the most wear-resistant among all the samples, even though it was not the hardest one. This finding means that hardness and grain size alone are not sufficient to predict trends in wear resistance.
10:10 AM
Microchemistry Evolution for 8xxx Alloys by Homogenization: Erik Santora1; Roland Morak1; 1Amag
In commercial Al-Fe-Si foil stock alloys, mechanical properties such as strength and ductility are influenced by the materials microchemistry. This study covers the general relation of microchemistry and the potential final softening behavior of aluminum foil, as described in the literature. In this paper, the focus lies on the evolution of solute content and microchemistry through different experimental homogenization practices for two 8xxx alloys with varying Fe and Si contents. The solute level, dispersoid phase volume fraction, and phase morphology of precipitated particles are investigated. The experimental results show a major temperature dependency of the solute content during homogenization.
10:30 AM Question and Answer Period Dr. Dimitry Sediako