Study on the laser selective melting and forming process and organizational properties of a TiSi2-modified 7075 aluminum alloy

To address severe defects, such as thermal cracks and high porosity, 7075 aluminum alloys were fabricated by selective laser melting (SLM). In this study, a 7075 aluminum alloy powder modified with TiSi2 was developed to control the quality of 7075 aluminum alloy specimens prepared by the SLM technique. The study investigated the SLM process and structural characteristics of TiSi2-modified 7075 aluminum alloy. It analyzed the reinforcing effect of TiSi2 particles in SLM-formed 7075 aluminum alloy. Results indicate that with laser power at 300 W, scanning speed of 800 mm/s, scanning spacing of 0.08 mm, and layer thickness of 0.03 mm, TiSi2-modified 7075 aluminum alloy specimens exhibit reduced cracking and pores, achieving a tensile strength of 559.13 MPa, 7.36 % elongation at break, and 98.8 % densification. These properties surpass those of conventionally SLMproduced 7075 aluminum alloy. The addition of TiSi2 promotes the formation of continuous equiaxed crystalline regions at alloy melt pool boundaries, reducing the average grain size from 8.847 mu m to 1.175 mu m and suppressing coarse columnar crystals. The mechanism involves Ti forming Al3Ti phases, acting as nucleation sites for heterogeneous nucleation. Si, along with the Al matrix, forms low melting point Al-Si eutectic structures, filling cracked areas during solidification; thus, preventing crack propagation. This process yields 7075 aluminum alloy with enhanced mechanical properties.