Gradient Structure of Ti-55531 with Nano-ultrafine Grains Fabricated by Simulation and Suction Casting

Optimizing the casting parameters of Ti-55531 is crucial in large aircraft castings. The thermodynamics parameters were simulated using the ProCAST software, and the properties of a gradient structure alloy with ultrafine microstructure were studied. The results indicate that the gradient structure of Ti-55531 with ultrafine grains is obtained. From the edge to the center, the gradient cooling rate decreases gradually from 88.83 to 52.79 degrees C/s and then to 37.51 degrees C/s as shown by the simulated parameters, resulting in the rapid solidification of the edge area to form the ultrafine grains. The hardness tends to strengthen with increasing radius in a gradient, from 3.67 +/- 0.12 GPa at the center, gradually increasing to 3.79 +/- 0.07 GPa at radius R1500, and finally reaching a maximum of 4.12 +/- 0.33 GPa due to the nano-ultrafine grains at radius R3000. A gradient structure can increase the strength-ductility of the Ti-55531 alloy. The compressive strength and strain are 3118 MPa and 69%, which are 36 and 30% higher compared to the non-gradient alloy. This study provides a new method for preparing gradient structures. Melting temperature of the arc melting can be calculated with T=1520.56+0.28xI\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\, T \, = 1520.56 + 0.28 \times I$$\end{document}.