▎ 摘　　要

NOVELTY - Preparation of graphene composite aluminum-based laminated gradient material involves adding 0.14 g graphene to 500 ml absolute ethanol, ultrasonically processing to obtain graphene suspension, adding 45 g pure aluminum powder, mechanically stirring at 300 rpm for 2 hours, filtering and drying to obtain mixed powder (A) containing 0.3 %mass graphene, weighing 5 portions of mixed powder (A) such as 10 g, 9.5 g, 9 g, 8.5 g and 8 g, respectively mixing 5 portions of mixed powder (A) with 0 g, 0.5 g, 1 g, 1.5 g, and 2 g silicon nitride powder to prepare mixed powders (B), sintering the mixed powders (B) in spark plasma sintering furnace at 560degrees Celsius to obtain single-layer materials, alternately laying single-layer material and pure aluminum powder in graphite mold, sintering for 20 minutes, cooling to obtain graphene composite aluminum-based laminated gradient material, post-treating and testing tensile strength, elongation and hardness of gradient material. USE - Preparation of graphene composite aluminum-based laminated gradient material used for impact-resistant protective armor used in military, national defense and other applications. ADVANTAGE - The graphene composite aluminum-based laminated gradient material has excellent structure density, no shrinkage or porosity defects, thin crystal grain size, and uniform dispersion of graphene and silicon nitride in matrix and well bonded interface, tensile strength of up to 335 MPa, elongation rate of up to 9.8% and hardness of up to 95 HV. DETAILED DESCRIPTION - Preparation of graphene composite aluminum-based laminated gradient material involves adding 0.14 g graphene to 500 ml absolute ethanol, ultrasonically processing at 720 W for 4 hours to obtain graphene suspension, adding 45 g pure aluminum powder, mechanically stirring at 300 rpm for 2 hours, filtering, drying to obtain mixed powder (A) containing 0.3 %mass graphene, weighing 5 portions of mixed powder (A) such as 10 g, 9.5 g, 9 g, 8.5 g and 8 g, respectively mixing 5 portions of mixed powder (A) with 0 g, 0.5 g, 1 g, 1.5 g, and 2 g silicon nitride powder by ball milling process to obtain mixed powders (B) with silicon nitride concentration of 0%, 5%, 10%, 15%, and 20%, sintering mixed powders (B) in spark plasma sintering furnace at 560degrees Celsius to obtain single-layer materials, cleaning graphite mold with absolute ethanol, adding single-layer material containing 20 %mass silicon nitride to graphite mold, spreading layer (A) of pure aluminum powder to thickness of 1-2 mm on single-layer material, adding single-layer material containing 15 %mass silicon nitride on pure aluminum powder layer (A), spreading layer (B) of pure aluminum powder to thickness of 1-2 mm, adding single-layer material containing 10 %mass silicon nitride on pure aluminum powder layer (B), spreading a layer (C) of pure aluminum powder to thickness of 1-2 mm, adding single-layer material containing 5 %mass silicon nitride on pure aluminum powder layer (C), spreading a layer (D) of pure aluminum powder to thickness of 1-2 mm, adding single-layer material component 0 %mass silicon nitride on pure aluminum powder layer (D), thereby completing laying of gradient laminated material, sealing mold, placing mold in graphite board of sintering furnace, setting parameter of sintering furnace, vacuuming sintering furnace to 10 Pa, opening water inlet valve, setting water inlet volume to 0.2-0.3 MPa, turning on the power air switch of the water pump to pump the cooling water back, setting sintering furnace temperature to 560degrees Celsius and heating rate to 80degrees Celsius/minute, driving the hydraulic pump to increase the head pressure to 20 MPa, and maintaining the pressure until the end of the temperature rise, sintering for 20 minutes, monitoring temperature in the furnace in real time, so that direct current pulse power sinters gradient laminated material, raising the head pressure to 50MPa, cooling furnace to below room temperature, demolding mold to remove graphene composite aluminum-based laminated gradient material, post-treating by cleaning outer surface of gradient material, polishing with 400-mesh sandpaper, cleaning with absolute ethanol, drying, testing tensile strength, elongation and hardness of laminated gradient material using electronic universal testing machine to analyze the tensile strength and elongation and analyzing hardness using Vickers hardness tester. The ball milling process involves adding mixed powder (A) and silicon nitride powder into the vacuum ball mill tank, adding 40 g grinding balls, so that the mass ratio of the ball to the powder to be mixed is 4:1, sealing the tank, vacuuming, introducing the argon gas into the vacuum ball mill tank to keep the pressure in tank at 1 atm, ball milling twice at 240 rpm for 1 hour each time, and stopping ball mill for 15 minutes after the first ball milling to cool down. The sintering process involves cleaning inside of graphite mold with metal shovel and metal brush, cleaning the inner surface of the graphite mold with absolute ethanol, adding mixed powder (B) to graphite mold, sealing the mold with thermal insulation carbon felt, placing mold in graphite board of sintering furnace, turning on the power and axial pressure device, adjusting initial pressure of the indenter to 10 MPa, making thermocouple hole on the graphite mold and the infrared meter hole and the thermocouple hole of sintering furnace component and infrared meter hole on the same horizontal line, closing the furnace door, closing vacuum valve, starting the vacuum pump, vacuuming sintering furnace to 10 Pa, closing vacuum valve and stopping vacuum pump, opening the water inlet valve, setting the water inlet volume to 0.2-0.3 MPa, turning on the power air switch of the water pump to pump the cooling water back, setting temperature increase rate to 80degrees Celsius/minute, driving the hydraulic pump to increase the head pressure to 20 MPa, and maintaining the pressure until the end of the temperature rise, sintering for 20 minutes when the temperature rises to the set temperature, monitoring temperature in the furnace in real time through thermocouple monitors, so that direct current pulse power sinters the mixed powder (B), raising the head pressure to 50 MPa, keeping the pressure head until the end of sintering, cooling furnace by water cooling, opening furnace door when the temperature of the sintering furnace is below room temperature, and demolding.