Fabrication and performance analysis of TC4 pyramidal lattice structures via alternating pin-press and brazing: A study on truss angle optimization

The 3D lattice structure is increasingly recognized in various applications due to its high porosity and excellent mechanical properties. However, fabricating these complex structures, especially using low-plasticity materials like titanium alloys, has posed significant challenges. The alternating pin-press method was successfully applied to produce titanium pyramidal 3D lattice core based on the high temperature forming mold. A brazing fixture was designed to protect the core during brazing, resulting in fully functional TC4 pyramidal 3D lattice structures. The fabrication structure achieved a compressive strength of 2.96 MPa and a relative compressive strength of 108.65 MPa at a relative density of 0.0272. Metallographic analysis revealed that forming at 800 ℃ resulted in equiaxed α phase with dispersed β phase, while brazing at 980 ℃, near the β-transformation temperature, led to coarse α and strip-like β phases. Experimental tests and finite element simulations demonstrated the variation in truss rod stiffness constant with geometry, identifying optimal truss angles of 33.4° for maximum flatwise compressive strength of 3.7 MPa and 44.8° for maximum relative compressive strength of 163.7 MPa. These findings offer valuable insights for the design of high-performance, low-density lattice structures in aerospace and related engineering fields.