Abstract:

Due to the special thermal neutron capturing ability of the¹⁰B isotope, B₄C/Al metal matrix composites (MMCs) have become increasingly used as neutron absorber materials in the nuclear industry. However, the addition of B₄C 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 30vol.%B₄C/6061Al 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：FSW>TIG 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/6061Al 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.

Key words: mechanical properties, microstructure, welded joints, B4C/6061Al composite