Work Package 1: Model scrap alloys with excessive impurities
Task 1.1: Within the frame work of CALPHAD (CALculation of PHase Diagram) approach PandaT commercial software were used in order to establish the phase relationships in terms of different isopleths in these alloy systems –
i. Al-Si-Fe system with Si (up to12wt% and Fe (up to 2wt%) .
ii. Al-Si-Fe-Cu system with Cu (up to 8wt%).
iii. Al-Si-Fe-Ni system with Ni (up to 8wt%).
Solidification behaviour of these alloy system has been predicted using equilibrium model and Scheil-Gulliver model.
Task 1.2: Based on the thermodynamic analysis the following model scrap alloys has been selected –
i. Al-(6-12wt%)Si-2wt%Fe
ii. Al-6wt%Si-2wt%Fe- (0-6wt%) Cu
iii. Al-(6-12wt%)Si-2wt%Fe- (0-8wt%) Ni
Task 1.3: In order to see the effect of different cooling rates two different types of casting methodology has been adopted, namely, gravity casting (GC) and high pressure die casting (HPDC).
WP2: Establish various approaches or method(s) to enhance the Fe-tolerance limit
Task 2.1: It was found that addition of Nb-B inoculation refines the grains in Al-Si alloys which has never been reported earlier. In fact it is worth mentioning here that commercial grain refiner Ti-B does not work in Al-Si alloy. However, neither Ti-b nor Nb-B was found to refine the β-phase in Al-Si-Fe alloys.
Task 2.2: Mn is known to destabilise the β-phase by promoting the formation of α-phase. Extensive work has been carried on to find the role of other alloying elements to destabilise the β-phase. It was found that addition of Cu and Ni beyond a certain concentration destabilise the β-phase by promoting Al7Cu2Fe and Al9NiFe phases, respectively.
Task 2.3: Morphological change of β-phase in both solid state and liquid state has been tried. It was found that the heat-treatment below the eutectic temperature (572oC) fragments the β-phase and spherodize the eutectic Si phase. On the other hand, heat treatment slightly above the eutectic temperature, at 580oC, refines the β-phase but promotes the growth of the Si particle in jagged needle like structure which deteriorates the overall mechanical properties of the alloys.
Task 2.4: HPDC process in cast alloys induces fine intermetallic phases. It was found that the size of the β-phase is smaller in HPDC alloys than in GC alloys. The difference in the size for the β-phase was clearly reflected in the mechanical properties of the same alloy in comparison to the GC alloys.
WP3: Study of intermetallic micro-mechanical properties
Task 3.1: Dissolution of aluminium matrix was carried out in 10%NaOH solution at room temperature in order to get the entire three dimensional structure of the β-phase. Scanning electron microscopy and x-ray diffraction analysis was carried out to characterize the extracted β-phase.
Task 3.2: Since it was found in Task 2.1 that no inoculation agent is capable of refining the β-phase; therefore no attempt has been made to prepare the pure intermetallic phase to see the effect of different inoculating agents.
Task 3.3: Microhardness testing along with tensile testing was carried out as per ASTME92 and ASTM B557 standard, respectively.
Task 3.4: The intermetallic phases in Al-Si-Fe-X alloys (X= Ni or Cu) was found to be in micrometer size. Field emission scanning electron microscope (FESEM) along with EDS and X-ray diffraction (XRD) technique were carried out to evaluate the phases and lattice parameters and volume fraction of all the phases present in any particular alloy. A summary of all tests done on specific alloys are listed under Section WP5.
WP4: TEM investigation on these Al-Si-Fe-X cast alloys were found unnecessary because of the large size of the precipitates and intermetallic phases. However, extensive microstructural characterization was carried out using FESEM, EDS and XRD, as detailed in WP5.
WP5: Develop a comprehensive database for mechanical property/intermetallic vs alloys composition: Based on the results obtained from optical microscopy (OM), FESEM, EDS (for elemental distribution and composition in the intermetallic phases), XRD, microhardness and tensile testing a comprehensive open database has been made. Such database will provide not only the photomicrographs of the concerning alloys but also the raw experimental data, thermodynamic data (phase diagram and solidification behaviour) and processed data. The following table lists all the alloys and characterization techniques that will be provided in this open database.
