An overview of the contents of the conference “Aluminium, the lightness of the metal, the versatility of its alloys” held on February 20th in Provagliod’Iseo with the aim of showing the many options offered by commercial alloys for extrusion, rolling, drawing, forging, additive manufacturing, castings and die castings
by Giuseppe Giordano
Organized by AQM, Alluminio&Leghe magazine and Metef, a Congress was held on February 20th with the significant title: “Aluminium, the lightness of metal, the versatility of its alloys”. The Congress was held in Provaglio d’Iseo, amidst the vineyards of Franciacorta, at the headquarters of AQM, a non-profit company founded in 1982, which works with national and international metallurgical and manufacturing companies, developing outstanding expertise on industrial materials in various fields of application, their production processes, the continuous improvement of the organization and the implementation of integrated management systems according to international standards in the various fields of application.
The event was a first example of partnership between Alluminio&Leghe magazine, AQM and Metef, the international aluminium exhibition which, besides its trade show aspect, has always provided operators with the opportunity of being informed about the latest news in the sector.
The central theme of the conference was the versatility of light metal as an asset for transformers and users of aluminium; versatility in the metallurgical sense as the choice of the right alloy in every circumstance and application requirement with the best possible combination of mechanical strength, formability, conductivity, corrosion resistance, suitability for decorative and protective surface treatments, mechanical machinability, recyclability.
This was therefore a technologically oriented conference aimed at creating new market opportunities for entrepreneurs, managers and technicians of aluminium transformation companies, to highlight that with a reasoned choice the maximum performance of the part and the finished component can be obtained, along with optimal production performance conditions.
The program of technical reports and testimonials was rich and complete, focused on the most significant options available among the commercial alloys for extrusion, rolling, forging, wire rod production, additive manufacturing, casting and die-casting.
The congress programme underlines this “universality” of metal technology and the presence of over 100 participants underscores the success of the initiative. During the congress fifteen reports were provided, subdivided into general presentations aimed above all at illustrating the different trends in the use of specific alloys in the various production sectors and presentations providing evidence of recent experiences of innovation.
All participants at the Conference were given the opportunity to download the entire iconographic material of the papers from A&L, AQM and Metef web sites. The opening speeches presented the market picture, with Paolo Kauffmann of FARO CLUB who analysed the non-ferrous metals sector and Mauro Cibaldi of Centroal-Assomet who presented the industrial segment of aluminium in Italy. In any case, we would like to refer readers to the detailed examination of the various reports, which they can request directly from the organizers. In this summary of the day we will briefly focus on some of the speeches which most impressed the public on account of their innovative contents.
Eural presents the new 2077 LF alloy for mechanical machining
In the following paragraphs we shall briefly discuss the speeches which described projects and products in whose development the choice of the alloy is of great importance.The day of the Congress was marked by a great success of an Italian aluminium industry which ought to be considered before the other projects offered by the congress.
One of the most famous family-owned aluminium companies in Brescia, EURAL Gnutti, developed a new alloy which, after passing all the complex checks required by the registration procedure, was officially included in the Aluminum Association’s list under number 2077. It is not at all easy to obtain the inclusion of an alloy in that list, even though the list has been in use for about sixty years and includes more than 550 specifications including plastic processing and foundry alloys. The obstacles are sometimes difficult to overcome, particularly for medium-sized companies. EURAL, represented by Sales Director Giorgio Di Betta, explained why it was necessary to develop a new hard aluminium alloy with high mechanical properties. Actually, there was a lack of a turning alloy that would create a fine chip for high productivity. Besides, some of the alloys used before this novelty presented stress corrosion cracking problems in different environments, which make it necessary to go through special heat treatments to stabilize the sensitivity to stress corrosion cracking; these, however, impair the tensile characteristics. For a deeper knowledge of the alloy’s characteristics, reference may be made to the specific article published on issue 1-2020 of Alluminio&Leghe, also available online.
New alloys and production processes for aluminium wire rod
Almost galvanized by the news of the registration of the new alloy, the Congress proposed a series of speeches, each of which would deserve an article, not only because of the data presented but also on account of the passion and commitment shown by the speakers. The task of the writer is to act as a reporter, choosing the themes to explore in depth among the memories requiring longer comments, pointing them out to those who were not there and providing a reminder for those who were present. Two memoirs concerning wire rod presented by Claudia Pizzanelli, Trimet, and Carmelo Maria Brocato, GMS, are part of this selection. Wire rod, very often, is forgotten both in statistics and in scientific memories. During the congress in Provaglio the fortunate coincidence occurred of having two speakers with great professional experience, one in the product sector, the other in the field of specific machinery. In Claudia Pizzanelli’s presentation, wire rod was the main player in the description of the products used in different sectors. It is particularly striking that a “mature” technology should be involved in new developments such as the electric car. To do this, the main road is that of metallurgical knowledge of products without fear of complexity. For instance, it has been shown that for wire rod for mechanical uses about fifteen different alloys are used in Trimet, which may be used in many physical states and with a variety of products with mechanical properties in the wide range shown in the same table.
The main use of wire rod is in electrotechnical applications. The importance of looking for new metallurgical solutions even for “electric” wire rod is, in my opinion, well represented by a picture presented by Carmelo Brocato: what better example could be provided of the importance of the lightness typical of aluminium than by showing exceedingly heavy electric conductors! The ice has weighted down the cables (usually copper cables with a steel core), but the effect could have been different if the conductor had been made out of aluminium, which is much lighter.
The step from wire rod to secondary smelting aluminium ingot is conceptually simple (there is in both cases the continuous casting of a bar) but technologically complex, as well illustrated by Brocato who pointed out the similarities and differences of the two processes.
Aluminium alloys as key players in Additive Manufacturing
New possibilities for light alloys have been provided in recent years by Additive Manufacturing technologies, which were discussed in the presentation by Paolo Folgarait (AQM-Seamthesis). Additive Manufacturing with the use of metal powders is today an increasingly widespread technology, not just in the academic field; more and more 3D printed parts are manufactured for industrial production rather than prototype use. Among the most studied metals, already used for many products and with the best development prospects, there are aluminium alloys offering a good supply availability often accompanied by an acceptable relationship between costs and performance. However, not all alloys can be used as they are because, depending on their chemical composition, they respond differently to sintering techniques with laser technology. Aluminium powders derived from such sintering processes may be subjected to definable mixing procedures in order to obtain the optimal composition for the three-dimensional printing of Additive Manufacturing. With these powders, very fine granular structures are obtained without having to add refining agents. The achievable tensile properties are high and in almost all cases good results are obtained in terms of endurance strength, creep, crack propagation and electrical properties. In some cases, however, there are reductions in plasticity which must be corrected with heat treatments, reducing the hardness of the alloy.
Starting from these general aspects of the new technique, the speech reported data on the characteristics of products obtained from powders of different alloys and developed with a didactic aspect useful to everyone.
An overview of the most widely used extrusion alloys
At every congress there is a favourite presentation for each of us. For me this was the one presented by Alberto Pomari on the trends in extrusion and rolling alloys. The author had the opportunity to present forecast figures projected up to the next decade. Finding so many data must have been hard and demanding work. These figures are scattered among various sources, sometimes also affected by the marketing strategies of major manufacturers. Fairly enough, where it was not possible to find official numbers, that very powerful judgement factor known as experience has been exploited. Those who have spent a good part of their professional life in the industries being considered “feel” how the market moves and “see” where technology is aiming. Thanks to their reflections and based on the comparison with other experts, they draw a trend line which does not need to be precise, but which does not reach the wrong target, even if it does not always hit the bull’s eye.
Innovative applications for aluminium foil
Aluminium foil is commonly identified with packaging applications, but in ProvaglioCiroSinagra, R&D manager of the LaminazioneSottile group, showed a very different application in the production of honeycomb panels, which from a niche product for aeronautical or sport applications has become a product used for the fitting of panels for various applications where lightness is the main demand.
Sinagra’s presentation described an application still intended for aeronautics in which the core of honeycomb panels is obtained with ENAW 5056 alloy sheet bonding techniques. From a metallurgical standpoint, it was interesting to follow the rolling process from the plate to sheets with a thickness of about 70 microns. Laminating an alloy with a magnesium content between 4.5 and 5.6% to these reduced thicknesses is a difficult and demanding process even for deformation equipment.
The presentation by Giampaolo Barbarossa, AITAL, on “Alloys for surface treatments” reminded us that the respect of the appearance and functional characteristics of the surface layer depends not only on the use of the correct parameters of the anodizing and surface treatment process and the use of suitable coating products but also on the evaluation of the chemical composition and metallurgical state of the aluminium alloy. The structural homogeneity of the semi-finished product is also an important factor.
The table shown, which lists and distinguishes the behaviour of the different intermetallic compounds present in the semis of various alloys, seemed particularly interesting. Specifically, some compounds (1) oxidise and dissolve very quickly and the oxide layer that forms is thin and porous. Other compounds (2) may give rise to partial dissolutions in the oxide layer while yet other compounds (3) remain embedded in it.
Low-carbon aluminium for the automotive sector
The presentation by Roberto Mastrangelo, Hydro, was divided into two parts, the first dedicated to the “green” product Reduxa™, the other aimed at presenting new alloys with high energy absorption capacity for automotive applications.
Reduxa is defined by Hydro as a “product”, but it is actually primary aluminium obtained with the utmost attention to environmental aspects, so much so that it has become a specific “Low-carbon aluminium”. The objective is to find the conditions to reach the target of 4 kilograms of CO2 per kilogram of aluminium by 2030 starting from a current European value of 6.7 kg and a global value of 18 kg, strongly influenced by the Chinese value of 20 kg determined by the great use in this country of coal for the production of electricity. Reduxa is produced only with renewable energy and with the maximum use of scrap metal. The quantitative aim linked to the use of Reduxa is to reduce CO2 emissions by about 4 million tons, equal to the emissions of 1.2 million cars.
The second part of the presentation was dedicated, as mentioned before, to the new alloys with high energy absorption capacity that Hydro is already partly producing industrially and partly still under R&D. These alloys are called HyCrush™. The figure shows the level of tensile properties which may be obtained with the different alloys according to their extrusion productivity. HyCrush alloys belong to the 6000 family but with different values of the ratio between Mg and Si which is in a wide range so as to have a differentiated energy absorption capacity.
New products in the foundry
Foundries, specific die-casting alloys, new applications in major development sectors were the topics of the second half of the conference. The presentation by Annalisa Pola (University of Brescia) on shell and die casting alloys was truly didactic and complete. It was a comprehensive lecture, full of tables, micrographs and images virtualized by SEM analysis. The slides collection could become an excellent online lesson: I would invite Professor Pola to think about it!
Few production sectors have undergone such intense changes as the aluminium foundry and, within the industry, the progress of die casting is even more surprising. It is impossible not to marvel at a Gigapress like the one presented by Riccardo Ferrario, General Manager of IDRA, commissioned by TESLA to realize an idea that at first sight appears to be a dream: to reduce the number of parts of the chassis of a car from 70 to four and then to one. The transformation of the dream into reality passes through the realization of the largest die-casting machine in the world. If today 70 robots struggle to assemble the chassis components, it is clear that the dream will also bring significant savings in terms of investment and management of an assembly line that will become much easier.
In the presentation by Enio Gritti, head of the FMB foundry (OMR Group), the author aimed at demonstrating that in castings the tensile properties are mainly determined by the distance between the branches of the dendrites expressed by the SDAS (Secondary Dendrites Arm Space) parameter and not by the type of alloy or even by the casting operations, but by the designers of the castings who define the casting branches, by those who design the moulds and by those who develop the casting simulation. I am not a foundry expert but it seems to me an interesting statement, certainly supported by an admirable experimental work. To demonstrate the above, both the primary 42100 alloy and the secondary 43000 alloy have been taken into consideration. They were cast in a mould after an intense cleaning of the furnace, good slagging and strong degreasing. Having fixed the mould temperature in order to have a liquid-solid transition in a few seconds and to generate structures with SDAS below 30 microns, tensile properties were found that were similar for the two alloys and at the maximum levels foreseen by the standard.
Stuart Wiesner from Aluminium Rheinfelden presented some alloys specifically developed for new structural applications in various sectors. For example, in the automotive sector these materials are used for heat exchangers, electric car battery containers, heating elements. Therefore, materials with good thermal and electrical conductivity are required. Among the slides of the presentation there are some tables that show the conductivity data as well as the tensile properties of various alloys in different physical states. For some alloys there are also the positive results of corrosion resistance and interesting data on the adherence of the molten alloy to the surface of the steel die-cast mould.
The last speech of the conference was delivered by Claudio Mus, Technical – R&D Director, EnduranceOverseas, who showed the possible present and future interactions between aluminium castings and electric mobility systems, that is, the different types of electric cars, scooters and e-bikes. The transition from internal combustion engine to electric or hybrid solutions requires a new design of many parts and the creation of components which are not present in traditional cars such as the battery container. It has been shown that the maximum use of aluminium castings is in hybrid solutions, which by definition increase the parts instead of replacing them. Aluminium is present in the production of batteries which not only power vehicles but also simpler machinery such as professional and hobby power tools, such as lawnmowers for parks and gardens. One aim is precisely to connect the different sectors. For instance, batteries in series mounted on cars, which maintain sufficient energy storage capacity at the end of the vehicle’s life, may be disassembled and used advantageously in other applications.