Application of Age Hardening Process to AA2011 Powders Produced by Oil Atomization Method

Abstract

AA2011 aluminium-alloy powders were produced in an atomization unit, which was previously designed and manufactured, by using the oil as atomization fluid. Negative influence of oxide amount on the produced parts was reduced compared to water atomization method. Test specimens were produced by pressing the powders into the mold. In addition, age hardening process was applied to these specimens and comparisons were made with the parts produced by rolling process. The results showed that there was a significant difference in the hardness values depending on the time. Introduction Part production by Powder Metallurgy (PM) is commonly used and it has become an alternative to the classical processing methods. High quality powders have to be used in order to fabricate the materials by using PM method. Production of metal powders by atomisation technique has an important place in the present time. In the litereture, there are three types of powder production methods such as water, inert-gas and air atomisation [1,2,3,4,7]. Gas and water atomisation, which are also called two fluid atomisation, are generally preferred for the production of high capacity powders [5]. However, there are certain limited properties of these powders produced by gas and water atomisation methods. For example, metal powders take the oxigen from the water, and oxigen percentages in the Al, Fe, Ni, Co and Cr alloys would become more than 1000 ppm. For this reason, in case of the usage of the powders produced by the water atomisation method containing high percentage of the oxigen, the notch impact strength of the produced parts decreases [1]. However, the oxigen rate in the inert-gas atomisation is lower than that of water atomisation. On the other hand, the cost of the gas becomes an important factor if argon and helium were used as inert-gas. The oxygen percentages in the metal powders produced by certain atomisation techniques are given in Table 1. In this study, the oil atomisation method was used instead of water in order to reduce the oxide amount in the produced powders. Table 1. The oxigen amount in the 125/45 μm powders of tin and AA2011