Design of Low-Cost and High-Strength Titanium Alloys Using Pseudo-Spinodal Mechanism through Diffusion Couple Technology and CALPHAD.

Chaoyi Ding,Libin Liu,Ligang Zhang,Di Wu,Chun Liu

doi:10.3390/ma14112910

Abstract

The high cost of development and raw materials have been obstacles to the widespread use of titanium alloys. In the present study, the high-throughput experimental method of diffusion couple combined with CALPHAD calculation was used to design and prepare the low-cost and high-strength Ti-Al-Cr system titanium alloy. The results showed that ultra-fine α phase was obtained in Ti-6Al-10.9Cr alloy designed through the pseudo-spinodal mechanism, and it has a high yield strength of 1437 ± 7 MPa. Furthermore, application of the 3D strength model of Ti-6Al-xCr alloy showed that the strength of the alloy depended on the volume fraction and thickness of the α phase. The large number of α/β interfaces produced by ultra-fine α phase greatly improved the strength of the alloy but limited its ductility. Thus, we have demonstrated that the pseudo-spinodal mechanism combined with high-throughput diffusion couple technology and CALPHAD was an efficient method to design low-cost and high-strength titanium alloys.

Highlights

Titanium alloy is an important strategic metal material with low density, high specific strength, and excellent corrosion resistance [1,2,3]
The diffusion couple specimen was cut in half, with one half being used as a solid solution sample and the other half being aged at 600 ◦C for 6 h
The data confirmed that Ti-6Al-10.9Cr alloy offered a saving of raw materials cost at 58% compared to the Ti-6Al-4V alloy, and the tensile strength of the designed Ti-6Al-10.9Cr is higher than that of Ti-6Al-4V alloy, while the Ti-6Al-10.9Cr had a poorer ductility. This suggested that substituting the expensive alloying element of V with lower-cost alloying element of Cr was an effective way to reduce the expense of implant materials and maintain high strength

Summary

Introduction

Titanium alloy is an important strategic metal material with low density, high specific strength, and excellent corrosion resistance [1,2,3]. The development, production, and characterization of low-cost titanium alloys are current research hotspots [13,14,15,16,17]. The CALPHAD method can be used to calculate phase composition, and fraction, driving force of phase transition and other characteristics affecting alloy properties in a short amount of time. It can provide effective guidance for alloy design, reducing the number of experiments performed. The Cr content of the alloy that has the ultra-fine α phase was determined using the pseudo-spinodal mechanism

Materials and Methods

Alloy Comparisons Based on Raw Materials Costs and Properties

Study Limitations and Potential Applications

Conclusions