Investigation of the Flow Behavior of Air-Cooling Ti-6Al-4V Alloy after Superplastic Forming

Xiaoning Han,Jinshan Li,Jianjun Wu,Junzhou Yang

doi:10.3390/cryst12020294

Xiaoning Han, Jinshan Li + Show 2 more

Open Access

https://doi.org/10.3390/cryst12020294

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Journal: Crystals	Publication Date: Feb 19, 2022
Citations: 3	License type: CC BY 4.0

Affiliation: Northwestern Polytechnical University

Abstract

The flow behavior of Ti-6Al-4V alloy during the air-cooling process after superplastic forming (SPF) has been discussed. In high-temperature constant strain rate tensile tests, the selected temperatures were 930, 900, 800, 700, and 600 °C, and the initial strain rates were 10−2, 10−3, and 10−4/s. The optimized deformation temperatures were 800~900 °C and the strain rates were 10−4~10−3/s. Then, the evolutions of activation energy and deformation strain are also discussed, and the effects of dislocation density and deformation activation energy on flow behavior were consistent. In addition, unstable flow is mainly concentrated in the low-temperature and high strain-rate regions, and this is mainly caused by dynamic recrystallization (DRX). After the SPF process, the possibility of material damage gradually increases during the air-cooling process.

Highlights

Ti-6Al-4V alloy is a polycrystalline metal with two isomers: α-phase with hexagonal close-packed (HCP) structure and the β-phase with body-centered cubic (BCC) structure [1,2,3]
The superplasticity of Ti-6Al-4V alloy refers to the properties that materials can achieve of great elongation without fracture within a certain range of temperatures and strain rates (10−4~10−2/s) [11,12]
The requirements of such high temperatures and low strain rates will lead to high costs

Summary

Introduction

Ti-6Al-4V alloy is a polycrystalline metal with two isomers: α-phase with hexagonal close-packed (HCP) structure and the β-phase with body-centered cubic (BCC) structure [1,2,3] It has the following mechanical properties: (i) low density and high specific strength; (ii) high temperature resistance; and (iii) excellent corrosion resistance. The superplasticity of Ti-6Al-4V alloy refers to the properties that materials can achieve of great elongation without fracture within a certain range of temperatures (about 900 ◦C) and strain rates (10−4~10−2/s) [11,12]. The requirements of such high temperatures and low strain rates will lead to high costs. The dislocation velocities are positively correlated with the strain rates [25], so the dislocation movement becomes more intense at a high strain rate

Deformation Activation Energy

Hot Working Process Maps

Conclusions