机械合金化后注射成形制备Cu/Al_2O_3复合材料的显微组织与力学性能

Microstructure and mechanical properties of Cu/Al_2O_3 composite prepared by metal injection molding after mechanical alloying

采用机械合金化后注射成形制备10%(体积分数,下同)Cu/Al_2O_3复合材料,研究机械合金化时间、烧结温度对复合材料显微组织和性能的影响,并分析复合材料的增韧机理。结果表明:通过机械合金化10h后注射成形、脱脂、1550℃烧结工艺制备的10%Cu/Al_2O_3复合材料具有良好的抗弯强度和断裂韧度,分别为532MPa和4.97MPa·m^(1/2);烧结温度低于1550℃导致原子在固态下扩散能力不足,烧结温度高于1550℃则使颗粒边界移动速率大于孔隙逸出速率,二者都造成复合材料孔隙率增加,而导致材料的强度和韧度下降;机械合金化时间延长使复合材料晶粒细化、Cu与Al_2O_3之间的结合强度提高,材料强度和硬度提高,但断裂韧度下降;Cu粉末弥散分布于Al_2O_3基体中,抑制烧结过程中Al_2O_3晶粒粗化,且使裂纹在扩展过程中遇到延性的Cu产生裂纹桥联和偏转,提高材料的韧度。

10%(volume fraction)Cu/Al 2O 3 composite was prepared by the process of mechanical alloying and powder injection molding, the effect of alloying time and sintering temperature on microstructure and properties of the composite was investigated, and toughening mechanism of the composite was analyzed. The results show that 10%Cu/Al 2O 3 composite with good bending strength and fracture toughness can be prepared by the process of mechanical alloying for 10h, degreasing and then sintering at 1550℃. Bending strength and fracture toughness of the composite prepared by this process are up to 532MPa and 4.97MPa·m 1/2 respectively. Due to weak diffusion of solid atoms for the composite being sintered below 1550℃, and mobility of particle boundaries being higher than pore escaping rate for the composite being sintered above 1550℃, porosity of the composite increases, and which results in strength and fracture toughness decreasing. Extending alloying time brings grain refinement and strong bonding between Cu and Al 2O 3 which is beneficial to elevate strength and hardness of the composite, while it is harmful to fracture toughness of the composite. Cu powders dispersing in the Al 2O 3 matrix protect the Al 2O 3 grains from coarsening during sintering process. And increasing in toughness of ceramic composite can be attributed to crack bridging and crack deflection when the cracks encounter the ductile Cu.