Gennaro Dionoro

FSW of AA 2139 Plates: Influence of the Temper State on the Mechanical Properties

Nowadays the fiber reinforced materials are finding more and more widespread use in aeronautic field due to their features of lightness, high strength and flexibility of manufacturing systems. The only way for metals to remain competitive for the aerospace applications is to improve new technologies and alloys in order to realize lighter and more resistant structures. The development of new alloys (lighter and stronger) and technologies will allow to use metals also in the future for aerospace applications. In this scenario the research activity has a fundamental importance, and the key point is to work simultaneously on both innovative materials and new technologies that allow to obtain the best performances with the innovative alloys. Welding is nowadays playing a fundamental role in transport industry thanks to the important advantages it allows. Friction Stir Welding (FSW) [1] is one of the most promising welding techniques, particularly suitable for applying to light alloys. FSW in butt joint configuration allows to achieve very high mechanical performances, often absolutely superior to those achievable with all other joining techniques, and lots of researches and results are now available [2]. The AA 2139 is an innovative Al-Cu-Ag alloy that has higher mechanical performances than the conventional 2xxx series aluminum alloys. The AA 2139 is designed to work in service in T8 temper condition, but is simplest to work in T3 temper condition. The aim of this work is to compare the performances of AA 2139 butt joints welded in T8 temper conditions, presented in a previous work [3], with the ones of joints welded in T3 condition and heat treated post welding in order to achieve the T8 temper condition.

Azides and nitrides in joints welded by laser using N2 as covering gas

A large amount of metals and alloys are successfully penetration welded by pulsed or cw laser. The laser welding process requires a gas flow (covering gas) to ensure adequate protection of the melt against atmospheric oxidation. The gas can be supplied in a variety of ways but in many cases the coaxial gas-laser geometry is used. This work is concerned with technological and structural investigations (using SEM and A.E.S. microanalysis) aimed at identifying any particular differences in the welds obtained using N2 instead of He as the covering gas. The investigations conducted on INCONEL 600 and stainless steel appear to provide conclusive evidence that N2 may be readily used as an alternative to He. Very recent works have studied some peculiarities (blanketing, transmission, and process efficiency) of N2 as a covering gas, when used in 2 kW CO2 laser welding. The influence of the covering gas in welding two stainless steels (AISI 304 and 430) and of a nickel alloy (INCONEL 600) using a 2 kW CO2 laser is examined.

Laser welding of INCONEL 600

Laser beam welding exhibits features typical of autogenous welding by fusion with very concentrated heat sources: narrow deep weld, restrict heat affected zone (HAZ), negligible residual.stresses etc. All these aspects are of great importance in welding special purpose alloys such as corrosion resistant nickel base alloys. In this work, a nickel base alloy INCONEIl 600 has been welded by means of a 2 kW C02 cw laser. In order to evaluate the influence of the basic welding parameters on heat affected zone, weld structure and weld geometry, an accurate analysis has been carried out. The experimental results show a strict correlation between the power beam and the welding speed vs. the weld bead geometry. As the speed increases, so penetration decays. Microhardness tests, micro and macrograph examinations did not reveal, in the range of experimental parameters, any significant alteration in weld bead structure nor the presence of a HAZ. In order to assess process efficiency, the experimental data were processed using the Line Source Model (LSM) which permits to calculate the Melting Ratio (MR) and Energy Transfer Efficiency (ETE)

Inert-Gas-Assisted Cutting of Low-Carbon Steel Sheets Using a High-Power Laser System

The high productivity that a laser system could have if employed in an integrated working system has induced the authors to confront the problem of cut surfaces obtained with laser technology. A cut of inferior quality would make a subsequent finishing operation necessary, which would weigh heavily on machining time.