Effect of Zr Addition on the Mechanical Properties and Superplasticity of a Forged SP700 Titanium Alloy.

Dong Han,Weidong Zeng,Yongqing Zhao

doi:10.3390/ma14040906

Dong Han, Weidong Zeng + Show 1 more

Open Access

https://doi.org/10.3390/ma14040906

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Abstract

The present study focuses on the effect of 1% Zr addition on the microstructure, tensile properties and superplasticity of a forged SP700 alloy. The results demonstrated that Zr has a significant effect on inhibiting the microstructural segregation and increasing the volume fraction of β-phase in the forged SP700 alloy. After annealing at 820 °C for 1 h and aging at 500 °C for 6 h, the SP700 alloy with 1% Zr showed a completely globular and fine microstructure. The yield strength, ultimate tensile strength and tensile elongation of the alloy with optimized microstructure were 1185 MPa, 1296 MPa and 10%, respectively. The superplastic deformation was performed at 750 °C with an elongation of 1248%. The improvement of tensile properties and superplasticity of the forged SP700 alloy by Zr addition was mainly attributed to the uniform and fine globular microstructures.

Highlights

The developed SP700 alloy, a β-rich α-β titanium (Ti) alloy, demonstrates high mechanical properties, pronounced superplasticity and excellent corrosion resistance, which make it an ideal structural material for applications in aerospace industries [1,2,3]
The duplex microstructures of SP700 alloy or other α + β Ti alloys are commonly optimized by the methods of heat treatment and/or adding of specific alloy elements [3,6,7,8,9]
The other reason is that the specific element can stabilize a lesser or greater volume fraction of β-phases

Summary

Introduction

The developed SP700 alloy, a β-rich α-β titanium (Ti) alloy, demonstrates high mechanical properties, pronounced superplasticity and excellent corrosion resistance, which make it an ideal structural material for applications in aerospace industries [1,2,3]. The duplex microstructures of SP700 alloy or other α + β Ti alloys are commonly optimized by the methods of heat treatment (annealing and aging) and/or adding of specific alloy elements [3,6,7,8,9]. One reason is that the microstructures typically rely on the allotropic transformation from a high-temperature bcc (β) phase to a lower temperature hcp (α) phase through the heating process [6]. The other reason is that the specific element can stabilize a lesser or greater volume fraction of β-phases. The addition of stable β-phase elements can decrease the transformation temperature of β-phase and lower the superplastic temperature. The purpose of this work is to improve the mechanical properties and superplasticity of the SP700 alloy to satisfy the high requirements of aerospace applications for complex structural materials

Materials and Experimental Procedure

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