Key Takeaways & Executive Findings
- •• Adding Nb to Ti-5552 alloy reduces the α/β phase transformation temperature, decreasing α phase volume fraction and affecting superplasticity. • Ti-5552-9Nb alloy exhibits optimal tensile strength (307.2 MPa) and superplasticity (106%) at 923 K. • Superplastic deformation at 923 K is governed by β grain boundary sliding and dislocation movement. • Achieving superplasticity at lower temperatures (below 0.5Tm) can reduce energy consumption and shorten production processes.
Abstract
Ti-5Al-5Mo-5Cr-2Zr-xNb with different Nb (abbreviated as Ti-5552-xNb, x=3, 6, 9, 12, wt.%) contents were stretched at 923 K to study their superplastic behavior and mechanical properties below recrystallization temperature. The microstructure of as-cast Ti-5552-xNb alloy is consisted of a single β phase, and the β grain size increases slightly with the increase of Nb content. The thermal effect in the process of high temperature drawing leads to the precipitation of α phase. The addition of Nb in Ti-5552 titanium alloys reduces the α/β phase transformation temperature, which causes a decrease in the volume fraction of α phase. Reducing the α phase content reduces incompatibility, but too low a proportion of α phase will lead to premature fracture, so tensile strength and plasticity firstly increase and then decrease. The results show that Ti-5552-9Nb titanium alloy shows the best tensile strength (307.2 MPa) and superplasticity (106%). The superplastic mechanism of Ti-5552-9Nb alloy is mainly caused by relative sliding of β grain boundaries and dislocation movement.
1. Introduction
Titanium alloy is widely used in various industries because of its excellent mechanical properties and high corrosion resistance [1-3]. With the development of aerospace, the application of titanium alloy has been paid more and more attention [4-6]. Cast titanium alloy has poor mechanical properties because of its coarse β grains, thus proper thermal deformation is considered necessary [7, 8]. Because of its softening mechanism, titanium alloy shows excellent superplasticity when temperature is higher than 1,073 K [9, 10]. In contrast, the plasticity is lower at lower temperatures. If superplasticity at 923 K can be achieved, it plays an important role in reducing deformation energy consumption and shortening the production process [11, 12]. For this reason, achieving superplasticity of titanium alloys at lower temperatures has attracted widespread attention from researchers. Among the current methods, alloying is one of the most promising ways.
Nb is an important alloying element in titanium alloy, which significantly improves the mechanical properties of titanium alloy [13]. In the previous research of our group, the addition of Nb element into the titanium alloy resulted in a significant improvement in room temperature strength [14]. In addition, Nb is also a β-stable element that plays a role in regulating the ratio of α/β phase [15]. Researchers have found that the ratio of α/β phase directly affects the superplasticity at 1,023 K [9]. At present, the research on superplasticity is still conducted at higher temperatures, and the mechanism by which Nb influences superplasticity at lower temperatures still needs to be revealed.
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Shi-chen Sun, Hong-ze Fang, Jia-qi Hao, Bao-hui Zhu, Xian-fei Ding, Rui-run Chen (2026). Influence of Nb addition on microstructure evolution and superplastic behavior of Ti-5Al-5Mo-5Cr-2Zr-xNb titanium alloy at 923 K. SinoTechIntel Verified Research. https://doi.org/10.1007/s41230-025-4248-1
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Frequently Asked Questions
What is the optimal Nb content for superplasticity in Ti-5552 alloy at 923 K?
The Ti-5552-9Nb alloy (with 9 wt.% Nb) exhibits the best tensile strength (307.2 MPa) and superplasticity (106%) at 923 K.
How does Nb addition affect the α/β phase transformation temperature?
Adding Nb reduces the α/β phase transformation temperature, leading to a decrease in the volume fraction of α phase during high-temperature deformation.
What is the superplastic deformation mechanism of Ti-5552-9Nb alloy at 923 K?
The superplastic mechanism is mainly attributed to relative sliding of β grain boundaries and dislocation movement.
Why is achieving superplasticity at 923 K important?
Achieving superplasticity at lower temperatures (below 0.5Tm) reduces deformation energy consumption and shortens the production process, which is beneficial for industrial applications.
What is the effect of α phase content on mechanical properties?
Reducing α phase content reduces incompatibility, but too low a proportion leads to premature fracture, so tensile strength and plasticity first increase and then decrease with Nb content.
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