Enhanced thermal coarsening resistance in a nanostructured aluminum-cerium alloy produced by additiv
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Henderson, Hunter B.↗
Engineering topics
Weiss, David
Publications and source records attributed to Weiss, David.
Overcoming the Barriers to Lightweighting by Enabling Low-Cost and High-Performance Structural Automotive Aluminum Castings
The major difference between the secondary and primary Al alloys is the amount of Fe in the alloys - recycling of Al alloys gradually leads to an increase in their Fe content. Thus, many secondary alloys allow up to 0.60% Fe as compared to the primary alloys that use between 0.10% and 0.20% Fe. Unfortunately, in Al alloys with higher iron content, iron-intermetallic phases form that are detrimental to the tensile properties and elongation of the Al castings. For example, in A356 alloys with iron at 0.10%, the ductility achieved is typically 8% whereas for secondary 356 alloys with iron around 0.6%, the ductility achieved is 3% or less. These intermetallic phases cannot be effectively modified with standard casting practices or standard heat treatment. Thus, new techniques need to be developed that can help secondary Al alloys overcome the mechanical property and cost barriers and are the focus of this project. We propose to lower the cost penalty and address mechanical properties issues in Al castings by a two-pronged approach: 1. Use an ultrasonics-based technique to modify the size and distribution of the deleterious intermetallics in the castings during the solidification process; and 2. Use PNNL-developed novel heat-treatment technique to lower the temperature and/or shorten the heat-treatment duration post-solidification processing.
36 MATERIALS SCIENCE↗
Development of a Castable High Strength Secondary Aluminum Alloy from Recycled Wrought Aluminum Scrap
A new process for recycling scrap AA7075 aerospace alloys directly into a high strength castable secondary alloy is demonstrated. The process involves enhancing the castability of the utilized primary wrought aluminum scrap feedstock by scrap alloy chemistry optimization and zirconium additions in order to mitigate the inherent hot tearing tendency of 7075 alloys. By utilizing the new process, the hot tearing index of scrap AA7075 was reduced from 26 to 4. Defect-free castings were obtained in pilot-scale castings trials. The developed secondary 7075 alloy also satisfied preset target mechanical properties with strength levels exceeding 250 MPa and elongation levels higher than 3%. The validity of the new approach and its readiness for transition to commercial practice was demonstrated by casting cylinder heads directly from the modified 7075 scrap.
36 MATERIALS SCIENCE↗
Anodization Compatibility of Eutectic Aluminum–Cerium Alloys
Anodizing is the most common method for producing corrosion resistant layer coatings for aluminum alloys. It is possible to use anodizing with most commercial aluminum alloys to increase material corrosion resistance, but often the brittle, passive oxide layer formed during anodization does not adhere well to the material, reducing effectiveness, and overall compatibility. Therefore, it is important for the compatibility and effect of anodization to be studied for any newly developed alloys. Recently developed eutectic Al–Ce alloys offer advantages like high castability, limited or no heat treatment requirements, and high-temperature strength retention. In this work, Al–Ce alloys are shown to have good compatibility with current processes and may exhibit improved adhesion of passivated layer because intermetallic phases anchor the anodized product to unconverted bulk. The source of these phenomena and their effect on material corrosion and layer adhesion properties of Al–Ce alloys will be discussed and compared with results from common commercial aluminum alloys.
Sims, Zachary↗
Operando measurement of lattice strain in internal combustion engine components by neutron diffraction
Significance Internal combustion engine components experience extreme thermomechanical cycling during operation, and the continuing need to improve engine efficiency while maintaining or improving reliability drives the development of lightweight materials with improved thermal and mechanical integrity. Understanding the behavior of new materials in dynamic operation requires operando characterization tools, but conventional in situ measurements of material behavior during real engine operation are very limited, and no practical means exist to replicate such extreme dynamics for ex situ study. In this work, we demonstrate that the penetrating power of neutrons can provide noninvasive measurement of lattice strains inside components of a firing engine, enabling the operando study of complex load states and thermal gradients throughout the solid materials.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Lattice strain and other supporting data from operando neutron diffraction study of a Honda GX200 engine with an Al-Ce cylinder head
Data repository for Operando measurement of lattice strain in internal combustion engine components by neutron diffraction. Data taken on VULCAN materials diffractometer at ORNL's Spallation Neutron Source.
36 MATERIALS SCIENCE↗
Thermodynamic Modeling of the Al-Ce-Cu-Mg-Si System and Its Application to Aluminum-Cerium Alloy Design
Recently discovered AlCe alloys have shown promise in a number of applications, but the propensity of Ce to react with Al and other alloying elements can complicate the phase equilibria and design approach. To solve this, the CALPHAD method is used to explore an alloy within the quinary Al-Ce-Cu-Mg-Si system by developing a thermodynamic database with self-consistent parameters. The database includes a description of all 10 binary systems and 8 ternary systems consisting of: (i) 6 Al-containing ternaries (Al-Ce-Cu, Al-Ce-Mg, Al-Ce-Si, Al-Cu-Mg, Al-Cu-Si and Al-Mg-Si); and (ii) 2 additional ternaries that include Mg and Si (i.e., Ce-Mg-Si and Cu-Mg-Si). The thermodynamic description for the Al-Ce-Mg and Al-Mg-Si systems were reassessed to ensure consistency with the binary systems and the Ce-Mg-Si system is presented for the first time and compared to theoretical data from DFT (Density Functional Theory). In addition to the ternary interactions, the quaternary compound Al3Cu2Mg9Si7 and solid solution extending from the ternary Al2CuMg phase (Al,Si)2CuMg are incorporated. The CALPHAD method is employed and leveraged through the use of a Materials Design Simulator (MDS) to accelerate the design of novel aluminum-cerium-based alloys. The combination of a CALPHAD-based framework with experimental efforts and industrial insight permits the development of three new Al-Ce alloys: Al-3.5Ce-0.4Mg-7Si (Ce-modified A356), Al-5Ce-1Cu-0.5Mg-10Si and Al-19Ce-0.9Mg-1.1Si.
36 MATERIALS SCIENCE↗
Thermomagnetic Processing of Aluminum Alloys During Heat Treatment
Processing materials under magnetic fields is an underexplored technique to improve structure and mechanical properties in metals and alloys. Magnetic fields can alter phase stability, modify diffusion characteristics, and alter material flow substantially. In castings, magnetic fields can be used during melting of the alloy, during solidification, or during postprocessing operations such as heat treatment to achieve structural changes. This work investigates the effectiveness of thermomagnetic processing during heat treatment of Al alloys containing in the Al–Cu, Al–Si–Cu, and Al–Mg–Ce systems. We demonstrate an improvement in mechanical properties and a reduction in required heat treatment times for all alloys.
36 MATERIALS SCIENCE↗
Surface-hardened aluminum-rare earth alloys and methods of making the same
Embodiments of surface-hardened aluminum-rare earth alloys and methods of making the alloys are disclosed. In some embodiments, the alloy comprises aluminum and 4 wt % to 60 wt % of a rare earth component X having a maximum solid solubility of ≤0.5 wt % in aluminum. The surface-hardened alloy component has an alloy bulk portion and a hardened alloy surface portion. At least a portion of the hardened alloy surface portion has a Vickers hardness that is at least 30% greater than a Vickers hardness of the alloy bulk portion.
36 MATERIALS SCIENCE↗