Production of B₄C/Al composites

The infiltration technique for fabricating B₄C-Al composites has been investigated. As the first stage of shaping B₄C preforms via slip casting, suspension stabilization conditions were determined by varying the pH level. A stabile suspension is obtained at pH 7 for suspension containing 35 mass % B₄C. Preformed samples were sintered at 2000°C for 30 minutes. Samples thus prepared had a theoretical density of 62.5%, flexure strength of 75 MPa and fracture toughness of 3 MPa.m^1/2 after the sintering process. Aluminum infiltration was conducted at 1100, 1150 and 1200°C for 15 and 30 minutes in a graphite resistance furnace under vacuum. Densities increase from 2.58 g/cm³ to 2.66 g/cm³ with increasing infiltration temperature for both 15 minutes and 30 minutes infiltration periods. Hardness of Al infiltrated B₄C changed from 5.3 GPa to 10.5 GPa for 15 minutes infiltration time and from 5.6 GPa to 11.8 GPa for 30 minutes infiltration time with increasing infiltration temperature. Flexure strengths and fracture toughnesses values decreased with increasing infiltration time and temperature. The highest flexure strength and fracture toughness obtained were 395 MPa and 15.25 MPa.m^1/2 at 1100°C infiltration temperature for 15 minutes infiltration time.