Manufacturing Ultrafine-Grained Ti-6Al-4V Bulk Rod Using Multi-Pass Caliber-Rolling

Taekyung Lee,Donald Shih,Chong Lee,Yongmoon Lee

doi:10.3390/met5020777

Taekyung Lee, Donald Shih + Show 2 more

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https://doi.org/10.3390/met5020777

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Abstract

Ultrafine-grained (UFG) Ti-6Al-4V alloy has attracted attention from the various industries due to its good mechanical properties. Although severe plastic deformation (SPD) processes can produce such a material, its dimension is generally limited to laboratory scale. The present work utilized the multi-pass caliber-rolling process to fabricate Ti-6Al-4V bulk rod with the equiaxed UFG microstructure. The manufactured alloy mainly consisted of alpha phase and showed the fiber texture with the basal planes parallel to the rolling direction. This rod was large enough to be used in the industry and exhibited comparable tensile properties at room temperature in comparison to SPD-processed Ti-6Al-4V alloys. The material also showed good formability at elevated temperature due to the occurrence of superplasticity. Internal-variable analysis was carried out to measure the contribution of deformation mechanisms at elevated temperatures in the manufactured alloy. This revealed the increasing contribution of phase/grain-boundary sliding at 1073 K, which explained the observed superplasticity.

Highlights

Titanium and its alloys have attracted attention from various fields such as structural-material, biomedical, munitions, and information-technology industries
It is obvious that the rod possessed the UFG structure with a grain size of 0.2 ±0.05 μm. Such a strong grain refinement has far been accomplished by severe plastic deformation (SPD) processes
According to the literature [27,37,38], such a microstructure is beneficial for the grain refinement through dynamic globularization because an initial lamellar thickness directly affects a final grain size

Summary

Introduction

Titanium and its alloys have attracted attention from various fields such as structural-material, biomedical, munitions, and information-technology industries. The alloy possesses a superior strength-to-weight ratio that increases the fuel efficiency of rocket and aircraft. It exhibits excellent corrosion resistance and mechanical stability at various temperatures. The alloy has good formability at elevated temperatures after applying a certain thermomechanical process due to the superplasticity [2,3,4]. Many researchers have focused on the fact that grain refinement can improve mechanical properties of titanium alloys. The grain refinement provides the increasing sources of grain-boundary sliding and induces the superplastic behavior at elevated temperatures

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