Tisi2 Modulation of Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloys

Abstract

Conventionally, Al-Zn-Mg-Cu alloys formed under the laser selective zone melting (SLM) process suffered from severe thermal cracking, which restricted the application of their formed specimens. To solve this critical problem, this paper has modified Al-Zn-Mg-Cu alloy by TiSi2 as reinforcing particles. The effect of the content of TiSi2 particles on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys was systematically investigated. By changing the SLM process parameters and the addition amount of TiSi2, a dense microstructure consisting of α-Al, L12-Al3Ti, β-Mg2Si and Al-Si eutectic microstructure was finally obtained, with fine crystals, no cracks, and a small number of pores, which effectively improved the thermal cracking phenomenon within the alloy and resulted in a significant increase in tensile strength and elongation at break. The results also show that the tensile strength of the alloy can reach 561.27±6.52 MPa, elongation after break can reach 7.41±0.4%, and hardness can reach 192.92±4.4 HV0.2. The L12-Al3Ti phase appeared in the intracrystalline and grain boundaries, and the strengthening mechanism of Ti and Si elements mainly originated from the synergistic strengthening of fine grains (ΔσHall-Petch), Orowan looping strengthening induced by particles such as L12-Al3Ti (ΔσOrowan), and load-transferring strengthening of precipitated phases (Δσload). This study is of great significance for the successful preparation of reinforced particle-modified high-strength aluminum alloys by SLM process.

Keywords: selective laser Melting (SLM), pyroclastic behavior, Al-Zn-Mg-Cu alloy, TiSi2, mechanical property；microstructure