The purpose of MagForming was to advance the state-of-the-art in the technology of plastic processing of wrought magnesium alloys for aeronautical applications, by developing tools and methodologies for industrial technologies and show their feasibility in Aeronautics. The measure for attaining the objective has been the fabrication of seven (7) prototypes, one for each of the technologies.
The most important advances of using wrought magnesium shapes have been achieved in the automotive industry. Most projects were focused on cast alloys and methodologies. Out of the few projects dealing with wrought magnesium only AEROMAG, of FP6 was explicitly concerned with aeronautic applications. It was evident from the research that the products currently achieved by forming processes of aluminium could be produced by upgraded processes of magnesium, but in a completely different domain of parameters. To date, none of the prototypes mentioned above have been manufactured with magnesium alloys.
The main objective of the MAGFORMING project was to develop several forming technologies for magnesium wrought alloys and to show their industrial feasibility in aeronautics. The measure that was used for attaining the objective was the fabrication of several prototypes for each of the technologies; also refer to as technology demonstrators (TDs).
The main objective was achieved by reaching the following sub-objectives:
- Methodologies for the preparation of the raw material for plastic deformation. Such preparation should include, among others, solidification processes, rolling processes, extrusion and annealing processes, etc.
- Study of the lubrication needs of the plastic forming of magnesium. For example, magnesium must be worked at high temperatures; therefore the lubricants must withstand high temperatures, unlike those for aluminium.
- The development of special heated dies with controlled temperatures and temperature gradients.
- The development of cooling procedures, to attain the best qualities for the manufactured part, as required by the specifications and, at the same time, preventing damage from the press machine.
- The development of a press loading application routine: level of force applied, temperature regime, duration of the application of force, process total speed etc.
- Some minor geometric modifications, within the parts design, using modelling software, to make sure that the magnesium part meets the specifications required by the end-users.
Three administrative work packages (WPs) (WP1 - Management, WP9 - Dissemination and exploitation and WP10 - Assessment and review) and seven technological WPs constructed the consortium framework. Out of the technological WPs, WP2 concentrated on selecting the TDs and the magnesium alloys for each technology, WP3 - WP7 concentrated in the different forming processes (forging, superplastic forming, pad forming, deep drawing and creep forming) and WP8 dealt with metallurgical investigation before and after the production processes.
The most crucial WPs were organised as follows:
- WP 2 This WP was led by Airbus. The TDs were selected according to their feasibility to achieve the aeronautic requirements and the potential economic advantages in regard to the conventional solutions. Then the available alloys and conditions (temper, semi-finished product form) were screened and the best suitable ones for the different TDs and special process requirements were selected.
- WP 3 In WP3 three TDs were manufactured by forging technology: A340 window frame, air system compressor wheel and A380 door stop fitting.
- WP 4 In WP4 two TDs were manufactured by SPF technology: G-150 service door inner panel and air conditioning system compressor scroll.
- WP 5 In WP5 two TDs were manufactured by pad forming technology: G-200 flap leading edge rib and Airbus pad forming reference part. Also a roll bending part was manufactured.
- WP 6 In WP6 one TD was manufactured by deep drawing and SPF technology: antenna support.
- WP 7 In WP7 one TD was manufactured by deep drawing and SPF technology: integral welded fuselage panel with stiffeners.
- WP 8 CUNI, acting as the metallurgical laboratory of MAGFORMING project, investigated the semi-finished material supplied to the different WPs by MEL and Alubin in order to understand the material prior to the forming processes and to find special parameters which facilitate simulation and production processes. Some of the issues investigated were: flow curve, yield and ultimate stress, thermal analysis, critical conditions for superplastic forming, optimisation of thermal processing and testing of raw material after optimised thermal treatment, SEM micrographs of fracture surfaces, analysis of phases, observation of microstructure, analysis of chemical composition, identification of processing temperature. This was done mainly for the forging, SPF and creep forming processes. In
The MAGFORMING project which aimed at manufacturing current aluminium made aeronautic parts out of magnesium alloys achieved its main goals. Structural parts which were initially selected as the demonstrators of the principal study were successfully manufactured through acceptable parameters and at reasonable costs. Mechanical and metallurgical properties of the produced parts were investigated and evaluated compared to end-users specification requirements.
These solid results might minimise hesitations of the aeronautic structural designers and engineers when considering the use of magnesium wrought alloys as well as their related production techniques. Yet magnesium is suitable for secondary structural and non structural parts.
Another conclusion which emerged from the project is the advantage of using specific magnesium alloys, such as WE43, as a suitable feedstock while forming processes are considered. This high strength magnesium alloy can be equal to certain aluminium alloys in respect of mechanical properties and working environment requirements. This alloy which is available in cast and wrought conditions can facilitate the use of magnesium alloys in aircraft parts.
Another conclusion which producers of aircraft parts can gain from MAGFORMING project is the option of modifying manufacturing methods and processes which can drastically reduce process.
Feasibility to forge a part like window frame from magnesium alloy has been confirmed which fulfils the main objective of MAGFORMING project. Both the AZ31 and the ZK10 sheet achieved perfectly the final geometries. AZ31B alloy showed better superplastic behaviour versus both 6061 and 5052 aluminium alloys.
Ecological calculation was expressed in energy terms of MJ (mega Joule). The calculations based on the power requirements of each stage. There are three major differences between the materials:
- Magnesium requires prior heating but it includes the power of the pressing machine.
- The energy of the coating is higher due to the specific technology used.
- Magnesium does not require heat treatment which lowers the number of stages, the duration of the product preparation time and the energy.
The bottom line is that magnesium requires fewer stages for manufacture and less energy. A more in depth approach to the calculations needs to be done for each part, if the material is switched all else equal, because it can be seen that 30% cost saving for raw material will result in an increase of 36% in weight.
In general, magnesium AZ31B sheet responds excellent to deep drawing and SPF apart, as well as to the combination of the two processes. Furthermore:
- The structure is stabilised during the SPF. No significant grain growth after deep drawing. No significant difference in microstructure between several locations along the formed parts.
- The preheating schedule has its dramatic influence on the process stages properties.
- The gas forming process is probably going forward through grain growth and following grain refinement under relatively high deformation stresses. The deformation mechanism must be grain boundary sliding (which causes the structure refinement) but not just it. There is clear evidence for conventional dislocation sliding which can be observed through the twins' bands. Based on the above, it is quite clear that the optimisation could be achieved by an effective and precise combination between heating schedule and internal pressure operated.
- There is no significant advantage in properties within 90 min SPF versus 30 min process. This fact shows that the combination of two-stage process definitely reduce the production schedule.