1,721,356 research outputs found
COMPOSITI A MATRICE DI ALLUMINIO: STATO DELL'ARTE E PROSPETTIVE DI IMPIEGO
No full textDi materiali compositi a matrice metallica e, in particolare, a matrice di alluminio si parla oramai da parecchi anni. Le potenzialità tecnologiche di questi materiali li rendono indubbiamente interessanti per diversi settori applicativi, ma un loro esteso impiego in ambito industriale non è ancora stato raggiunto. In questo lavoro vengono presi in rassegna processi produttivi e caratteristiche dei compositi a matrice di alluminio di maggior interesse, cercando da un lato di evidenziare i fattori che ne hanno finora limitato le applicazioni e, dall’altro, di individuare le possibilità di sviluppo
GETTI IN GHISA: ANOMALIE DA SOLIDIFICAZIONE
No full textObiettivo di questa memoria è quello di presentare una rassegna delle principali anomalie microstrutturali riscontrabili in getti in ghisa, cercando di illustrarne le cause. Tali anomalie sono, in linea di principio, suddivisibili in tre categorie:
- anomalie associate alla solidificazione,
- anomalie associate al raffreddamento successivo alla solidificazione e/o a trattamenti termici,
- anomalie di altra origine
LA PRESSOCOLATA SOTTO VUOTO: LIMITI E POTENZIALITA'
No full textThe potential and the problems of the conventional diecasting process are well known. One of the most critical points is certainly the phenomenon of gas entrapping by the molten alloy during the filling of die cavity. The high speed reached by the molten alloy, together with the complex geometry of the die cavity, gives place to highly turbulent conditions. Thus, air and gases can be entrapped into casting, even if overflows are employed. Besides, the entrapped air significantly increases its pressure, making more difficult the progress of filling. The use of vacuum diecasting allows the significant improvement of diecastings quality, and is critically reviewed in this paper
I DIVERSI PROCESSI DI FONDERIA
No full textRassegna dei processi di fonderia utilizzati per realizzare componenti automotive in lega di alluminio
Note sullo sviluppo e sulle innovazioni della fonderia di alluminio
No full textSono presi in rassegna gli sviluppi più significativi della fonderia delle leghe leggere, con riferimento agli ultimi decenni
UNIONE EUROPEA: I PROGETTI DI RICERCA
No full textRassegna dei progetti di ricerca condotti in ambito UE nel settore automotive
Microstructure, defects and properties in aluminium alloys casting: a review
No full textMicrostructure, defects and final mechanical behaviour in castings are strongly correlated and inter-dependent. With specific reference to Aluminium alloys cast products, the present paper is aimed at describing
- firstly the more frequently encountered defects in castings,
- then the typical microstructure that can be achieved
- and finally how defects and microstructure are affecting the mechanical properties of such castings.
The need of an integrated knowledge about these aspects is outlined, in view of an efficient and optimised design of cast components manufactured using Aluminium alloys
Aluminium alloy castings: the EU StaCast guide to defects classification, mechanical potential and design issues
No full textThe European Aluminium alloys foundry industry (more than 2000 Companies, mostly SMEs) has an enormous potential, associated to the increasing demand of lightweight components in various application fields, from automotive to aerospace.
This potential has still to be fully exploited. European Aluminium foundry industry is now facing the challenge of transforming itself into a quality/efficiency-driven and integration-oriented sector. This target requires the achievement of several intermediate objectives, such as the development of new and advanced Standards and Technical Reports, supporting a systematic improvement in design and production of high quality and highly performing cast components.
This is the scenario in which the EU financed StaCast project (FP7-NMP-2012-CSA-6, Grant n. 319188) has been carried out, with the joint effort of University of Padova (Italy), Aalen Hochschule Technik und Wirtschaft (Germany), Trondheim Norges Universitet (Norway), Associazione Italiana di Metallurgia (Italy), Assomet Servizi (Italy), and Federation of Aluminium Consumers Europe (Belgium).
The acronym StaCast means “New Quality and Design Standards for Aluminium Alloys Cast Products”, and the Project has been focussed on
- a public survey of EU Aluminium foundries, to understand their more relevant characteristics, particularly for what concerns quality and standardisation issues,
- the development of a reliable classification of defects and imperfections in Al Alloys cast products, transferred to CEN (European Committee for Stardardisation) as an official Technical Report,
- the development of a procedure for the evaluation of mechanical potential of Aluminium-based foundry alloys, transferred to CEN (European Committee for Stardardisation) as an official Technical Report,
- the elaboration of engineering guidelines for the mechanical design of Al alloys castings.
These four issues are substantially described in the four Chapters of this book.
As coordinator of StaCast, my wish is that this book could be useful for the persons involved in Aluminium foundry industry, and my thanks are for all the colleagues which very cooperatively worked in this Project
Microstructural investigation on aluminium castings for automotive applications
No full textIn the diesel engine cylinder head, especially to resist to high combustion pressure, it has been demanded to develop high strength materials. The traditional cast iron cylinder head meets most of the requirements. However, cast iron has the disadvantage of being heavy and having a low thermal conductivity. To improve the fuel efficiency and the drivability of vehicles, light weighted cylinder heads made of aluminium alloys have been developed. In recent production, Al-Si-Cu-Mg cast alloys have been used so far because of their good performance of castability and mechanical strength with age hardening.
This work analysed the microstructural properties of the mentioned cast aluminium alloys on two real complex-shaped castings like diesel cylinder heads, as cast and T6 heat treated, experimentally produced by Teksid Aluminum. The secondary dendrite arm spacings (SDAS) and the size and morphology of eutectic silicon were considered with this study under quantitative aspects. It is well known how finer SDAS, obtained with high solidification conditions, result in more uniform microstructure and create the condition for more closely distributed and finer, smaller particles, like eutectic silicon and intermetallics. In this study the cast aluminium alloy (A354) adopted to cast cylinder heads underwent a heat treatment (T6) in order to obtain an optimum combination of strength and ductility. The mechanical properties of this alloy are generally dependent by the followings conditions:
distribution and size of the precipitates, β-Mg2Si and θ-Al2Cu,
structure and size of eutectic silicon particles.
Therefore, it is evident how the mechanical properties of the casting are severely influenced by the combined effect of SDAS and eutectic silicon
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