Aluminum Alloys, Processing and Characterization: Plasticity and Mechanical Behavior
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Yanjun Li, Norwegian University of Science and Technology
Tuesday 2:00 PM
February 28, 2017
Location: San Diego Convention Ctr
Session Chair: Pizhi Zhao, Chinalco
2:00 PM Introductory Comments
New Yield Criterion for Description of Plastic Deformation of Face-Centered Cubic Single Crystals: Nitin Chandola1; Crystal Pasiliao2; Oana Cazacu1; B. Revil-Baudard1; 1University of Florida/REEF; 2Air Force Research Laboratory
In this paper an analytical yield criterion for description of the plastic behavior of face-centered cubic single crystals is presented. The new criterion is written in terms of the generalized invariants of the stress deviator proposed by , specialized to cubic symmetry. The octahedral projections of the yield surfaces for different crystal orientations according to the new model are presented, and compared with the yield surfaces according to the regularized Schmid law [2,3].
Quantifying As-cast and Homogenized AA7050 Mechanical Properties through Compression Testing: Yunbo Wang1; Matthew Krane1; Kevin Trumble1; 1Purdue University
Prior studies of as-cast AA7050 mechanical property are sparse, and the mechanical properties are usually measured with uniaxial tensile tests. In order to generate data for simulation of stress development in direct chill (DC) casting, compression tests were performed on AA7050 samples in both as-cast and homogenized conditions in the temperature range of 20 to 500 °C at strain rates from 10-4 to 10-2/s to strains of ~0.5. Results from test specimens having round and square cross-sections with L/D = 1.5 were compared to each other and to published tensile data. The flow stress-strain data is fit to the Ludwik equation to generate constitutive laws for the flow stress as a function of strain, strain rate and temperature. The effect of microstructural changes from as-cast to homogenized structures on mechanical properties is discussed.
Determining a Stable Texture Condition Under Complex Strain Path Deformations in Face Centered Cubic Metals: Usman Ali1; Abhijit Brahme1; Raja Mishra2; Kaan Inal1; 1University of Waterloo; 2General Motors Research and Development Center
Evolution of texture components during deformation of lightweight aluminum alloy sheet under different strain paths is studied by analyzing the evolution of element rotation calculated using a rate-dependent crystal plasticity finite element model. Based on a stability criteria proposed by Ali et al., 2016, data from cold rolling and shear simulations is analyzed to determine stable texture components. The predicted stable texture components, for the same microstructure, for rolling and shear using the stability criteria are in-line with experimental observations. Further analysis of simulated data yields a simpler methodology that stable texture components are those that are aligned with the loading direction. Using this methodology, stable textures under rolling and shear are analytically identified and the results show an excellent conformity to experimental data. This new methodology can be included in robust non-texture based phenomenological modelling to predict texture evolution in engineering design problems.
Microstructural Transition and Elevated Temperature Tensile Properties of Modified Al-Si-Cu-Mg Alloys: Mehdi Rahimian1; Shouxun Ji1; Paul Blake2; Douglas Watson2; Zhongyun Fan1; 1BCAST, Brunel University London; 2Jaguar Land Rover Limited
In order to improve the mechanical properties of aluminium alloys used in automotive powertrain at elevated temperatures, the chemical composition of Al-Si-Cu-Mg alloys is modified by addition of transition elements. In comparison with the commonly used EN-AC-42000 alloy, the new aluminium alloy can significantly improve tensile properties at elevated temperatures. Microstructural investigation revealed that tuning of chemical composition can refine the strengthening phases and increase their volume fractions in the aluminium alloy. SEM observation demonstrated the existence of well distributed phases in the microstructure of the Developed alloy. As a result of microstructural modification, yield strength of Developed alloy is enhanced versus Base alloy (EN-AC-42000). The multiple strengthening mechanisms are responsible for the property improvement.
3:45 PM Break
Effects of Alloying Elements on Anneal-hardening Behavior of Aluminum Alloy Foils: Takashi Suzuki1; Shigeru Kuramoto2; Masaya Endo1; Qi Cui1; 1Mitsubishi Aluminum Co., Ltd.; 2Ibaraki University
we observed that non-heat treatable al-fe-mn alloy foils exhibit an increase in strength and a decrease in elongation due to low temperature annealing treatment subsequent to cold rolling. in this presentation, we investigate the effects of alloying elements on the anneal-hardening behavior. the aluminum alloys without alloying element of fe were not hardened by low temperature annealing treatment. on the other hand, the anneal-hardening behavior was observed only in al-fe based alloys containing mn, cr, or zr. in the al-fe-mn alloy foils before and after annealing, no fine precipitate particles could be observed in tem, and no peak on the dsc curves could be observed. these results are similar to “hardening by annealing” reported on severe plastic deformation of metal.
Increasing Strength and Corrosion Resistance of AlMgSi Alloys by Tailor-made Thermomechanical Processing: Alexander Wimmer1; 1Neuman Aluminium
The impact extrusion process of aluminum is an important manufacturing method for production of semi-finished products. Actually AlMgSi (EN AW 6xxx alloys) are impact extruded in a soft state (0 condition), however a heat treatment on the final products is needed to generate a high ductility and strength (T6 condi-tion). Through this heat treatment deformations on the final product could occur and new process routes have to be developed. In this work the deformation re-sistance, strength and corrosion resistance as a function of thermomechanical processing and microstructure were analyzed.
Microstructural Optimization of a High Mechanical Properties (HMP) Aluminum Alloy by Using CobaPress™ Process: Mamadou Balde1; Christophe Desrayaud1; Véronique Bouvier2; Frédéric Perrier2; 1Mines Saint-Etienne; 2Saint-Jean Industries
CobaPress™ process is a hybrid process of casting and forging leading to the manufacturing of high integrity/critical safety components and sub-assemblies for the automotive industry. Throughout this process, the main objective consists in the elaboration of an aluminum alloy with yield strength of 300MPa and at least 8% of elongation. The use of Thermocalc© simulations allowed us to set up with annealing temperatures and chemical composition. Channel die experiments have been carried out to study sub-structure evolution for a fixed temperature and different strain rates. Observations on EBSD have been made in order to characterize recovery and/or recrystallization. Apart from the fact that sub-structuration improves yield strength and ultimate tensile strength, fatigue life is much greater than AS7G03 usually used trough the CobaPress™ process.
Cyclic Stress-strain Behavior and Low Cycle Fatigue Life of AA6061 Aluminum Alloy: Mirza Foisal Ahmed1; K. Liu1; X. Grant Chen1; 1University of Québec at Chicoutimi
AA6061 alloy is one of the most widely used aluminum alloy in modern aerospace and automotive industries due to low cost, good formability and high specific strength. Most of aluminum structural components experience dynamic loading, which leads to fatigue failure. Since studies on the strain-controlled fatigue behavior of these alloys are very limited, this study was aimed to evaluate the strain-controlled cyclic deformation behavior of an extruded 6061 aluminum alloy, and determine the fatigue life under varying higher strain amplitudes. The stress-strain responses exhibited essentially symmetric responses with slight Bauschinger effect. A slight cyclic hardening occurred at high strain amplitudes (0.6-1.2%) within the first ten cycles, and then cyclic stabilization follows until failure. It had a longer fatigue life which can also be described by the Coffin–Manson law and Basquin's equation. Crack initiated from the specimen surface and crack propagation was characterized by fatigue striation-like features.