Spray-formed hypereutectic aluminium silicon alloys offer great potential to be used for technical components when excellent mechanical properties and low weight are required. These alloys can be produced to have higher stiffness, greater high temperature strength, excellent wear resistance and a reduced coefficient of thermal expansion compared with cast or wrought aluminium alloys,e.g.AlSi17(AlSi17Fe4Cu3Mg) alloy,it has the following benefits,
1)Because spray forming is a single-step Powder Metallurgy (PM) process, production costs are substantially lower compared with conventional PM alloys.
2)Currently, spray-formed hypereutectic aluminium silicon alloys are, for example, used for spool valves, oil pump gears and connecting rods. AlSi17,also called DISPAL S232 by Peak Wertstoff GmbH, – T6x, which is the subject of the present investigation, is used for highly stressed components at elevated temperatures. Spray forming of AlSi17 allows blending with 17% Si and 4% Fe besides Cu and Mg, which leads to strengthening Fe and Si components. Heat treatment T6x indicates peak ageing with the aim of improved ductility.
3)Performed strain-controlled tests with nine different alloys. Several correlations between static and cyclic properties of the different spray- formed alloys were developed for the low cycle fatigue regime. Additionally, they investigated the influence of notches with different stress concentration factors on lifetimes of two alloys in load-controlled fatigue tests and interpreted their findings considering the volumes of highly stressed material. Components of engines and aggregates may be loaded with a very high number of cycles during service, in the range of up to one billion. High cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of AlSi17(Dispal S232) – T6x were investigated by Stanzl-Tschegg.
4)The chemical composition of AlSi17(DISPAL S232) is (in % weight): Si 17%, Fe 4%, Cu 3%, Mg 1%, Zr < 1% and balance Al. The heat treatment consists of solution annealing, quenching in water and artificial ageing. The designation T6x indicates Peak ageing treatment with slightly lower tensile strength and improved ductility compared with T6. Compared with T6, the heat treatment T6x leads to longer fatigue lifetimes in the HCF regime.
5)AlSi17 shows a high Young ’ s modulus, high strength and outstanding wear resistance. The manufacturing process starts with melting the alloy and spraying it through a nozzle into a nitrogen atmosphere. A spray of droplets falls onto a rotating plate. Small droplets are already solidified when they reach the plate, whereas bigger droplets are semisolid or still completely liquid. The droplets form a film that solidifies very quickly, avoiding any segregation. A billet is formed on the rotating plate that is machined afterwards. Then, the material is extruded to eliminate porosity and subsequently heat treated.
6)With the mechanical properties of good grindability,abrasive stability and high stiffness,resistance even at high temperature.Whilst the provided AlSi17 materials are compliance with RoHS directive 2011/65/EU.