MICROSTRUCTURE AND MECHANICAL PROPERTIES OF HOMOGENIZED STIR CASTING ALUMINUM BRONZE ALLOYS

Abstract

In demand to the industrial needs to produce Cu-Al alloys with controlled chemical compositions. The present research focuses on the production of Cu-Al alloys with different aluminum additions of 1.9, 3.6, 5.8 and 7.7 wt. % by stir casting method in argon atmosphere. Then, homogenized treatment was done for these alloys at 850 oC in different periods of soaking time of 2, 4, and 6 hrs to determine the best conditions for increasing the mechanical properties. This is carried out in the α phase region. The microstructure of the samples is analyzed by using Optical and Scanning Electron Microscopy (SEM) with (EDS). The results showed the mechanical properties of copper were increased with increasing in Aluminum content. The microstructure of the castings consist of the dendiritic structure, columinar grains and segregation. The results showed that after homogenization, the microstructure changed to fine grains, elimination of the columnar segregation and the clusters disappeared. The XRD results show that the phases are α (Cu-rich) phase as highest peaks and the small amount of CuAl2 phase. The best Aluminum content value was 7.7 wt % and the soaking time 4 hrs were given the high hardness 204 Hv and the highest ultimate tensile stress value of 383.8 Mpa