The role of Nd on the microstructural evolution and compressive behavior of Ti-Si alloys

The rare earth (RE) added Ti-Si alloys are potential candidates for lightweight structural materials, especially in high-temperature fields, but up to now related fundamental information is still rare. In this work, samples of Ti-8Si-5Nd, Ti-13Si-5Nd, and Ti-20Si-5Nd are designed to investigate the effect of RE element Nd on the microstructural evolution and compressive properties of the Ti-Si alloys. Experimental results indicate that all the samples are composed of α-Ti, β-Ti, Nd and Ti5Si3 phases according to the XRD patterns. The Ti-8Si-5Nd alloy shows a typical hypoeutectic structure with primarily precipitated bulky Ti5Si3 and Nd. Ti-13Si-5Nd alloy has lamellar eutectic structure and the Ti-20Si-5Nd alloy exhibits a coarsened homogeneous primary Nd, Ti5Si3 precipitation and microcrystalline eutectic structure. The added Nd and primarily-precipitated Nd5Si3 particles work as inoculants and refine the grain size of Ti5Si3, because of their similar hexagonal structure, atomic bond and atomic distribution of the outer crystal surface. The refined grain size and homogeneous distribution of Ti5Si3 phases in the Nd added Ti-Si alloys (especially the hypoeutectic alloy) are effective to improve the mechanical properties. The Ti-8Si-5Nd alloy exhibits the best plasticity (14.545%) and compressive strength (1191 MPa) among the three samples and shows good potential for structural materials.