Aluminum matrix composites reinforced with hexagonal boron nitride particles
The present paper was focused on the investigation of mechanical properties of Al-based composite materials reinforced with commercially-available BN micro- and nano-particles. Particular attention was paid to the study of different methods of preparing Al-BN mixtures to achieve homogeneous distribution of the BN phase within the Al powder.
To obtain homogeneous Al-BN mixture, four different methods were utilized: (i) ultrasonic treatment, (ii) tridimensional, (iii) roll and (iv) magnetic mixing techniques. The modern technique of high energy ball milling was also explored. The mixtures were pressed and sintered with a spark plasma sintering machine in a graphite die. The obtained disc samples (30 mm diameter) were cut in several dog-bone shape specimens suitable for the tensile test. The mechanical properties were evaluated using the tensile test and the Vicker's hardness test.
The best results were achieved using ultrasonic mixing with 4.5 wt% nano-BN and further ultrasonication: 10 min. nano-BN + 20 min. nano-BN with Al. The tensile tests revealed values which are 180 % higher (260 MPa) than for pure aluminum (92 MPa).
With the ball mill mixing technique, the highest tensile strength was obtained for 5-7 wt% micro-BN composites. The tensile strength (385 MPa) was 320 % higher than for pure aluminum. Using ball mill mixing technique we obtained an additional 48 % increase in tensile strength compared with the ultrasonic method. The hardness tests applied on the ball milled specimens confirmed the highest hardness for the Al-7 wt% BN.
The next step is to continue the mixing with the ball milling technique and optimize the parameters of time and speed in order to obtain the best routine for the fabrication of aluminum matrix composites reinforced with hexagonal BN nanoparticles.
Scientific adviser - Ph.D. Shtansky Dmitry Vladimirovich