The main application of 319 aluminum alloy is for manufacturing components for automobile industry. One of the main concerns related to the recycling of this metal is regarding the incorporation of impurities as iron, for instance. Due to its low solubility in solid aluminum, the presence of this element leads to the formation of intermetallic compounds such as α-Al8Fe2Si and β-Al9Fe2Si2, the most common iron phases in Si-containing Al-alloys. The β phase is harmful to mechanical properties because of its platelet like morphology. Spray forming is an advanced processing technique which can mitigate the deleterious effect of these intermetallic phases. However, the solidification process of spray formed metals is still an open discussion. In these sense, the aim of this work is to contribute to a better understanding of the solidification process of spray formed 319 aluminum alloy. The work was divided in three stages: the first evaluated the presence and morphology of intermetallic phases by varying the pouring temperature and Fe content (0.6 and 1.2 in mass percent); the second evaluated the eutectic Al-Si morphology through varying the processing conditions; and finally, the third evaluated the solute distribution in the final microstructure, in this case other aluminum alloys were studied together with the 319 (2024 and 7050). The basis for discussion the phenomena was a solidification model for spray formed metals recently proposed in the literature, which defines the process in two stages, being the final solidification occurring at low cooling rate. The results showed that by controlling the processing parameters it is possible to mitigate the β-Al9Fe2Si2 formation, as well as to alter the eutectic Al-Si morphology. The third stage indicated the possibility of maintenance of certain solute in solid solution on the periphery of aluminum grains. It could be concluded that the solidification model was adequate to explain the phenomena presented in this work.

Solidificação da liga de alumínio 319 conformada por spray

Modified Al alloys are gaining emphasis in the past few years due to wide range of properties available for the
engineering applications. These alloys are manufactured by spray forming process have superior properties over the
conventional cast alloys. Hence in this article an attempt has been made to summarize the work that has been carried out in the
field of spray forming of hypereutectic Al – Si alloys and with other alloying elements such as Fe, Cu, Mg and Mn. As
hypereutectic Al – Si alloys are attractive for the industrial applications due to their low thermal expansion co – efficient and high
tribological properties. In this study attention has been paid towards the microstructure, mechanical and tribological properties of
the studied alloys. The study of process parameters over the size and shape of the powder in spray forming is other part of this
work. The change in properties of spray formed alloys by the working of secondary process is also been considered.

Spray Deposition Process of Hypereutectic Al – Sialloys: An overview

OPTIMIZATION OF THE MECHANICAL PROPERTIES OF IRONCONTAINING 319 ALUMINUM ALLOY The influence of iron additions (0.6, 0.8, 1.2 and 1.5 wt.%) and heat treatment on the microstructure and tensile properties of the 319-aluminum alloy processed by spray forming and rotary swaging was investigated. The spray-formed deposits were rotary swaged at 573 K with an area reduction ratio of 5:1. Room temperature tensile tests showed a substantial increase of elongation at fracture (5.5-8%) when compared to the values observed for the iron-containing conventionally cast counterpart (0.6%). The high values of elongation at fracture were obtained due to the significant microstructural refinement and decrease of volumetric phase fraction, especially the iron-rich intermetallics, promoted by the combination of spray forming and rotary swaging. Moreover, the heat treatment is responsible for the silicon globulization, dissolution of θ-Al2Cu blocks and dramatic improvement of ductility (16-17%).

Otimização das propriedades mecânicas da liga de alumínio 319 contaminada com ferro

In this study, the dependence of Er addition (0-0.49 wt %) on the microstructural evolution and related tensile strength at high temperature (HT) were investigated for the eutectic Al-Si piston alloys. The results showed there were intermetallic compounds of -Al3CuNi, -Al7Cu4Ni, Al4Cu2Mg8Si7, β-AlFeSi and Al3(Er, Cu, Fe) (Ni, Si) 2 identified at T5 states. Herein, the added Er element has led to the formation of the star-like and the irregular-shaped Al3(Er, Cu, Fe) (Ni, Si) 2 phase. The phase was stable which showed little change in both size and composition experienced solid solution at HT during the T6 treatment. For the HT strengths (350 oC), the T5 state alloys have higher UTSs than those at T6 state, both of which were reduced gradually with the increasing Er contents. The variation of HT strengths caused by the Er addition was explained by the microstructral evolution, namely Al3(Er, Cu, Fe) (Ni, Si)2 phase formation

/pdf/effect-of-er-addition-on-the-high-temperature-strength-of-al-3o4eks0t8y.pdf

Effect of Er Addition on the High Temperature Strength of Al-Si-Cu-Ni-Mg-Fe Piston Alloys

....................................................................................................... I Dedication .................................................................................................. III Acknowledgements ....................................................................................... IV Publications, conference presentation and beam times awarded ......................... VI

Modelling and experimental study of the spray forming of dissimilar metals

The microstructural characteristics and mechanical properties of Al–6.5Si and Al–18Si alloys have been investigated. The alloys were spray-deposited and hot extruded at 480C with an area reduction ratio of 6:1. The microstructure of the spray-deposit of Al–6.5Si alloy
showed spherical morphology of the primary a-phase with a globular shape of the eutectic Si phase in the inter-particle boundaries. On the other hand, a fine particulate morphology of primary Si phase uniformly dispersed in the matrix of the a-phase was observed in spray-deposit of Al–18Si alloy. Microstructural refinement was further increased in the hot extruded alloys. The room temperature tensile tests of spray formed and extruded alloys showed considerable increase in their strength and ductility over that of the as cast alloys. The improvement in mechanical properties of spray formed alloys is discussed in light of the microstructural modifications induced during spray deposition process.

V C Srivastava

Papers

Microstructure and mechanical properties of Al–Si alloysproduced by spray forming process