Impact Toughness Anisotropy of TA31 Titanium Alloy Cylindrical Shell after Ring Rolling.

Haiyang Jiang,Hao Zhang,Jianyang Zhang,Bijun Xie,Mingyue Sun,Bing Wang,Zhangxun He,Yuxi Wu,Bin Xu

doi:10.3390/ma13194332

Abstract

The impact toughness of a TA31 titanium alloy cylindrical shell was investigated systemically after ring rolling. The impact toughness of specimens with different notch orientations shows obvious anisotropy. The microstructure of the cylindrical shell and the impact fracture were characterized by an optical microscope and scanning electron microscope. The results show that cracks are easier to propagate in the equiaxed α phase than the elongated α phase. This is because the expanding cracking path in the equiaxed α phase is shorter than that in the elongated α phase, and thereby the cracks are easier to propagate in the equiaxed α phase than the elongated α phase. More specifically, the α phase on the RD-TD plane was obviously isotropic, which makes it easy for the cracks to propagate along α grains in the same direction. However, the α phase on the RD-ND plane has a layered characteristic, and the direction of the α phase varies from layer to layer, thus it requires higher energy for cracks to propagate across this layered α phase. Therefore, the cracks propagating in the same α phase orientation take easier than that in the layered α phase, so it has lower impact toughness.

Highlights

Titanium alloy is widely used in manufacturing key components for aerospace engineering, due to its high specific strength, low density, superior corrosion resistance and good process performance [1,2,3,4,5].Titanium alloy with a composite microstructure of equiaxed α and transformed β, in which the α phase accounts for 50%, generally has excellent ductility and fatigue resistance [6,7,8,9]
The α phase exhibits a bright contrast under the optical microscope, while the contrast of the β phase ofof the αα phase is is primary equiaxed α phase, while the phaseisisdark dark(Figure (Figure4).4).InIngeneral, general,the themajority majority the phase primary equiaxed α phase, while phase is dark (Figure 4)
The following conclusions can be made: (1) The TA31 titanium alloy cylindrical shell was formed by upsetting, punching, saddle forging, core bar stretching and ring rolling

Summary

Introduction

Titanium alloy is widely used in manufacturing key components for aerospace engineering, due to its high specific strength, low density, superior corrosion resistance and good process performance [1,2,3,4,5].Titanium alloy with a composite microstructure of equiaxed α and transformed β, in which the α phase accounts for 50%, generally has excellent ductility and fatigue resistance [6,7,8,9]. Nakase et al [10] studied the influence of the microstructure parameters produced by α+β forging and heat treatment on the strength and ductility of Ti-6Al-4V. They suggested that the strength and ductility have strong correlations with the aspect ratio of the primary α phase and increase linearly with the decrease in the aspect ratio of the primary α phase. Qin et al [11] found that the full lamellar microstructure of Ti-5553s alloy can transform into a bimodal microstructure during α+β forging.

Results

Discussion

Conclusion