快速热压法制备B_4C/Al中子吸收材料的力学性能

Mechanical properties of B_4C/Al composites for neutron absorption fabricated by rapid hot-pressing

采用粉末冶金快速热压法制备B_4C/Al中子吸收材料,对其进行T6态热处理,通过对材料的密度、硬度与抗弯强度等性能的测试以及材料微观组织、物相组成和弯曲断口形貌的观察与分析,研究成形压力、热压压力与温度以及B_4C颗粒含量的影响。结果表明,B_4C/Al复合材料的物相组成为Al和B_4C;B_4C颗粒均匀地镶嵌在基体中,颗粒与基体结合紧密。材料密度随压制压力增加而增大,随B_4C含量增加而降低,在热压压力和温度共同作用下,铝合金液充分填充压坯孔隙从而实现高致密。当B_4C的质量分数为30%时,在150 MPa预成形压力下压制、530℃/10 MPa条件下热压后所得B_4C/Al复合材料的相对密度最高,达到99.87%,断裂方式为韧性断裂。经T6态热处理后,硬度HB和抗弯强度均提高,分别达到123.49和394.117 MPa,断裂方式转变为脆性断裂。

B4C/Al composites for neutron absorption were fabricated by a rapid hot-pressing method using different cold forming pressure, hot pressing pressure, temperature and B4C content. Subsequently, the composites were processed by T6 heat treatment （solid-solution strengthening at 530℃ for 2 h, water quenching and ageing strengthening at 180℃ for 12 h）. Mechanical properties of the composites were measured and the microstructure, phase composition and fracture morphology were systematically investigated by means of optical microscopy, XRD, SEM and EDS. The experimental results show that, there are no new phases generated in B4C/Al composites, B4C particles are uniformly embedded in Al matrix, and the interfaces between particles and matrix are well combined. Moreover, the densities of the composites increase with increasing pressure and decreasing B4C content, respectively. And with the co-effect of hot pressing pressure and temperature, the Al liquid can fully fill in pores of the composites to achieve high densities. The relative density of the composite with 30% B4C obtains the maximum value of 99.87% when being treated by 150 MPa cold forming pressure and 10 MPa hot pressing at 530℃. After T6 heat treatments, the hardness and bend strength of composites both increase, and reach 123.49 HB and 394.117 MPa, respectively. The fracture mode transforms from ductile fracture into brittle fracture.