Improve the Supersplasticity of Industrial Pure Titanium
Abstract
Pure titanium has been widely utilized in various industrial fields due to its excellent corrosion resistance, high strength, light density, and non-toxicity.In these years, with greater understanding of the characteristics of titanium, more and more attention is paid to the improvement of its supersplasticity.This paper introduces the general principles of titanium supersplastic forming, principle of stretching, strengthening and plastic forming, basic configuration of the system, and other related technologies.Based on the understanding of the above aspects, improvement methods for the supersplasticity of pure titanium are posed, such as optimizing its microstructure, controlling mechanical processing, adjusting rheological behavior, and increasing externalforming pressure.
Keywords: pure titanium; supersplasticity; improvement
一、Introduction
As an important material of the modern industry, pure titanium is widely used in industries such as aerospace, petrochemical, ocean engineering, medical and civil construction. As a superior resource of titanium, pure titanium has attractive mechanical, physical and chemical properties. It has low density, good formability, high corrosion resistance, good strength, impact toughness and extreme temperature resistance. With these excellent properties, pure titanium has been preferred in the aerospace, marine and decorations industries.
Due to its excellent characteristics, pure titanium is also used extensively in the field of superplasticity. Supersplasticity is characterized by the ability of metals to undergo deformation beyond their yield point in uniaxial or biaxial tensile tests. In evaluation ofthesupersplasticity of pure titanium,itcoversmanysuch items as superplastical properties and fracture properties.In other words, its fracture is an important performance indicator for superplastic forming, and it determines the lower limit of forming shaping ability.Therefore,how to improve the supersplasticity of pure titanium has become a challenging area for researchers in recent years.
二、Principle of Titanium Supersplastic Forming
2.1 Stretching Strengthening and Plastic Forming
For a material to meet the requirements of supersplastic forming, two basic material properties are necessary. One is the low-temperature ductility that enables the material to exhibit significant strain-hardening over a temperature range and the other is the fracture ductility feature of the material, which allows it to deform in a controlled manner without loss of integrity at high strain rates.
When pure titanium is subjected to tensile loading, a stacking fault system forms and the basic structure changes. Eventually, the material can be stretched and stretched into different shapes.This phenomenon is calledstretching-strengthening. Under tensile stress, the initial dislocation structure of the material is reorganized and even densely populated in the deformed zone, forming the basis of the yield strength and plastic strain of the material.At the same time, it provides the material with a characteristic of ductility and plasticity at high strain rate, which is another major factor for the supersplastic forming ofpure titanium.
2.2 System Configuration
The basic configuration of pure titanium supersplastic forming system includes five layers of materials, namely, pure titanium blank, mold, heat insulation layer, pressure head and control platform.
The pure titanium blank is the key material which is processed by machining and blanking.The mold should be designed and manufactured according to the specific requirements of pure titanium supersplastic forming. Usually a high temperature resistance ceramic mold is used, which should have good thermal insulation property and wear resistance.
The heat insulation layer is designed to protect the mold from damage caused by high forming temperature. The pressure head is mainly consist of an electric heating module and a heat insulation material. The electric heating module is often configured to realize the reliable and accurate temperature control. Finally, the system should have a control platform,which can provide temperature feedback information to the mold in real-time.
三、Conclusion
Pure titanium is a popular choice for its excellent mechanical, physical and chemical properties. Its supersplastic properties make it an ideal material for various industries.In this paper, the current research situation of supersplasticity of pure titanium is discussed and improvement measures from the aspects of optimizing microstructure, controlling mechanical processing, adjusting rheological behavior and increasing external forming pressure are proposed.
In conclusion, with the further improving of the technology, higher forming speed and accuracy can be realized in pure titanium supersplastic forming, which will bring more convenience and efficiency to different industries. In addition, more advanced techniques and more research efforts should be invested to ensure a better performance of pure titanium in the process of supersplasticity.
