چكيده به لاتين
Nowadays Aluminum based composite materials found vast applications in aerospace and automobile industries. In preset study two kinds of reinforcement materials of Alumina and BNi-2 (Ni-7Cr-3.12B-4.5Si-3Fe) alloy were used simultaneously for fabrication of composite material. For introducing reinforcement materials into the aluminum alloy matrix, first, a groove of 2 mm depth and 2 mm width was machined at the surface of a 5 mm thickness Al-Mg alloy sheet, then, a mixture of Alumina and BNi-2 powders was placed at the groove and laser remelted. For next step, the remelted and solidified structure was processed with different passes of friction stir processing (FSP) method and final composite was fabricated.
The composite was studied by scanning electron microscopy, hardness test, bending strength test and fractography. According to the results, by the increase of friction stir processing numbers from 1 to 5 passes, the amount of the reinforcements crushing and dispersing increases. However, the chance of BNi-2 clustering increases by the increase of volume fraction of Alumina in the mixture of reinforcement powders. In addition, the heat generated by the laser beam causes the reaction between Aluminum and Nickel (of BNi-2). Using the mixture of powders leads to increase of hardness from 94 HV in initial Al-Mg alloy sheet to 151 HV in the sample with 75% volume fraction Alumina, 25% volume fraction BNi-2, after 5 passes of friction stir processing. Furthermore, bending strength increases from 3800 N in initial Al-Mg sheet to 7500 N in the sample with 50% volume fraction of Alumina and BNi-2. Increment of the numbers of passes in FSP of the samples that have the Alumina powder, solely, leads to the fracture with semi-brittle surface. The samples only contain BNi-2, show ductile fracture.
