CHARACTERIZATION OF ALUMINUM ALLOY-BASED NANOCOMPOSITES PRODUCED BY THE ADDITION OF AL-TI5-B1 TO THE MATRIX MELT

Abstract

The present study is an attempt to produce aluminum matrix nanocomposites using a certain aluminum alloy (which its melt has high fluidity) as a matrix material and reinforced with hard and stable fine (nano-sized) precipitates. Therefore, Al-Ti5-B1 master alloy and Al-Si alloy of high silicon content were proposed for preparation of such nanocomposites. Three nanocomposites were prepared by adding Al-Ti5-B1 of three different percentages (1, 2 and 3 wt. %) to the melt of aluminum alloy at 710°C for a holding time of 10 min and application of mechanical stirring at this temperature. Finally, the treated melt was squeeze cast. The microstructures were investigated using optical and scanning electron microscopes. Phases and different constituents were analyzed with the aid of EDX and XRD analyzers. The addition of Al-Ti5-B1 master alloy with any percentages (even 1 wt. %) to the melt of aluminum alloy, led to remarkable decrease of the matrix grain size. Moreover, many fine precipitates were detected within the Al-Si matrix such as TiAl 3 phase in the form of flaky and blocky morphology and TiB 2 phase in the nano-sized particles. These precipitates act as heterogeneous sites for nucleation during solidification. The addition of Al-Ti5-B1 master alloy to the Al-Si base metal led to remarkable increase in the average hardness. As the added percentage of Al-Ti5-B1 master alloy is increased, the average hardness value is increased. The average hardness of addition of 3 wt. % Al-Ti5-B1 master alloy reached 130 HV, which was almost twice as high as the hardness of the Al-Si base metal.