Aluminium Technology - Miscellaneous
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FOUNDRY
Magazine 2023/3
THE BIFILM REVOLUTION IN AL METALLURGY
J. Campbell
Department of Metallurgy and Materials, University of Birmingham, UK
Abstract
The turbulence during the handling and pouring of liquid has been traditionally overlooked as the source of the major defects in aluminium alloys. The entrainment of the liquid surface effectively folds in the surface oxide, dry-top-side to dry-top-side, so that no bonding can occur between these two ceramic surfaces. The absence of bonding gives the double film the character of a crack. Bifilms form huge populations of cracks in Al alloys, greatly affecting properties such as elongation and fatigue. They have not previously been recognized because they can be extremely thin, only a few nanometers thick. The entraiment defect which is even more serious is an air bubble, for reasons which are described.
Current integrated plants producing slabs by direct chill (DC) process are seen to be poorly designed, with inappropriate furnaces and melting procedures, and poor transfer conditions, and which therefore suffer severely from bifilm multiplication resulting in cracked slabs and the high cost of upgrading or remelting.
The implications for the presence of bifilms throughout aluminium metallurgy at this time is spelled out: the evolution of metallurgy from (i) the discovery around 1900 of atoms and the point defects, vacancies, to (ii) the invention of the electron microscope to observe line defects, dislocations, in around 1950, to finally (iii) the observations of planar defects, bifilms, in about 2000, is seen to complete, for the first time, the necessary building blocks of a cogent and full understanding of aluminium metallurgy.
The bifilm concept predicts that all crack initiation in metals may be the result of the presence of bifilms: the implication being that bifilm-free metals will be incapable of failure by cracking. This is revolutionary thinking that the industry will need to take on board.
In practice, the bifilm populations in Al alloys can be reduced by various techniques which will be described. The techniques are not especially costly to install, but are expected to greatly reduce costs, and greatly raise quality to levels previously unattainable. The prospects for bifilm-free Al alloys is exciting, and appears to be already possible. It promises to revolutionise aluminium production world wide. (Read Full Article)
ALLOYS
Magazine 2023/2
MICROSTRUCTURE AND PROPERTIES OF A NOVEL ZR-MICROALLOYED HIGH-STRENGTH AL‑MG‑SI ALLOY
F. Zupanič, T. Bončina, University of Maribor, Faculty of Mechanical Engineering, Slovenia
P. Cvahte, M. Steinacher, Impol Group, Slovenia
C. Gspan,Institute of Electron Microscopy and Nanoanalysis, Austria
Abstract
In this work, we investigated a modified Al-Mg-Si alloy (AA 6082). The main new alloying element was zirconium, however, also the additions of other elements were slightly modified. The alloy was characterised in the as-cast condition, after homogenization, extrusion, and T6 heat treatment using light microscopy, scanning and transmission electron microscopy with different microanalytical techniques, X-ray diffraction, differential scanning calorimetry, tensile, fatigue, and corrosion tests. In the modified AA 6082 alloy, the tensile strengths between 460 MPa and 500 MPa were achieved. The low-cycle fatigue strengths were comparable to similar alloys. The corrosion resistance of the alloy was slightly better in comparison to other copper-containing 6xxx alloys that are on the market (EN AW 6110A) but slightly worse than in 6xxx alloys without copper.
The excellent mechanical properties are based on the presence of Al3Zr and -AlMnSi-dispersoids and nanosized ’-Mg2Si and Q’-AlCuMgSi precipitates in the matrix. (Read Full Article)
Magazine 2023/2
IMPROVEMENT OF INTEGRATED HANDLING SYSTEMS FOR ALUMINIUM PRODUCTION CHAINS: MOVING ALUMINIUM FROM UPSTREAM TO DOWNSTREAM
D. Trenti, DimaSimma Intralogistic Srl, Italy
C. Minari, DimaSimma Intralogistic Srl, Italy
Abstract
Both the technological and economical researcher state that the factory of the future has to be automatic and strongly integrated. European Governments call this trend “4th industrial revolution” or “industry 4.0” or “smart factory”.
Some steps are indispensable to reach this goal:
- Advanced Manufacturing Solutions: i.e. interconnected, flexible and highly efficient manufacturing system
- Horizontal and vertical integration by data exchange
- CPS: Cyber Physical System, i.e. physical system strictly interconnected with IT, able to interact and cooperate with other CPS.
In the aluminium field, DimaSimma is applying these concepts since many years:
- 2005: realization of the first integration within automatic storage, commissioning and painting
- 2008: design and realization of a logistic system for a full-integrated extrusion factory. The logistic system has an automatic storage for 4400 basket and keeps 250 basket in movement in the different production area of the factory: painting, anodizing, commissioning, thermal break, wood effect, packaging and delivery.
- The most recent application is the integration of AGVs with storage system and automatic stacker cranes. The AGVs and the automatic stacker cranes retrieve and deposit the baskets in the stations that interconnect the automatic warehouse with the different process area.
Advantages are: efficiency, traceability, flexibility, safety, competitiveness.
Same concepts of advanced manufacturing and integrated solutions have been applied also for dies, slab, coils and so on. (Read Full Article)
