B_4C/6061Al复合材料焊接接头组织与力学性能研究

Microstructure and Mechanical Properties of B_4C/6061Al Composites Welded Joints

基于碳化硼中^(10)B同位素优良的热中子吸收能力,铝基碳化硼复合材作为中子吸收材料越来越多的应用于核电站中。但碳化硼颗粒的加入使该材料的可焊性变差,因此研究其焊接行为变得十分必要。采用钨极氩弧焊(Tungsten inert gas,TIG)和搅拌摩擦焊(Friction stir welding,FSW)对体积分数为30%的B_4C/6061Al复合材料进行焊接,研究不同焊接方法、焊缝填充材料对复合材料对接接头微观组织及力学性能的影响。B_4C/6061Al复合材料焊接接头拉伸性能如下:FSW焊>TIG焊(Al-Si焊丝)>TIG焊(6061Al焊丝)>TIG焊(6061Al-Mg焊丝)>TIG焊(无填充)。TIG焊缝区容易产生气孔、B_4C颗粒分布不均匀及有害生成相是导致其力学性能不佳的主要原因。FSW可以有效避免基体金属与增强相的高温化学反应,使得焊缝区的晶粒细化,增强相颗粒的分布比TIG焊均匀,为30%B4C/6061Al复合材料最佳焊接方法,其接头的室温拉伸强度达247 MPa,为母材强度的85%。

Due to the special thermal neutron capturing ability of the 10B isotope,B4C/Al metal matrix composites（MMCs） have become increasingly used as neutron absorber materials in the nuclear industry.However,the addition of B4 C particles deteriorates the weldability of B4C/Al MMCs,thus it is necessary to investigate the welding behavior of this composite.The microstructure and mechanical properties of welded joints of 30 vol.%B4C/6061 Al composites are investigated by using tungsten inert gas（TIG） welding and friction stir welding（FSW）.The results of the tensile strength are shown as follows：FSWTIG welding（Al-Si filler metal）TIG welding（6061Al filler metal）TIG welding（6061Al-Mg filler metal）TIG welding（no fill metal）.The reasons for the poor mechanical properties of TIG welding are mainly attribute to the generation of defects（such as pores,unevenly distribution of B4C particles and harmful phase） in welding.The FSW is identified as optimum welding method for B4C/6061 Al composites,which can avoid the high temperature chemical reaction between the matrix metal and reinforcing particles,and producing fine recrystallized grains in the Al matrix,and the B4C particles are uniformly distributed in the weld joints.The tensile strength of the FSW joint is about 247 MPa,which is 85% of the base material.