Effect of microstructure on tensile properties of Ti-17 alloys forged using a 1500-ton forging simulator

Yoko Yamabe‐Mitarai ,Hiroaki Matsumoto ,Norie Motohashi ,Yoshinori Yoshida ,S Kuroda ,Kazushi Yamanaka ,Gorō Miyamoto ,Mitsuo Niinomi ,Yoshio Itsumi

doi:10.1051/matecconf/202032104014

Abstract

Microstructure dependence on mechanical properties were investigated for Ti-17 forged at temperatures between 700 and 850 ˚C with deformation ratio from 33 to 80 %, and solutiontreated at 800˚C for 4 hours and aged at 620 ˚C for 8 hours. The microstructure was observed after solution and aging treatments. The volume fraction and the size of the primary alpha phase was controlled by solution treatment temperature, not forging temperature and deformation ratio. Forging temperature affected the morphology of grain boundary (GB) alpha phase. Deformation ratio affected the grain size and the aspect ratio of the horizontal and vertical grain size of the prior beta phase. The tensile strength was investigated at room temperature, 450, and 600 ˚C. Forging temperature and deformation ratio did not affect the tensile strength because there is no large difference of the volume fraction of the alphaphase. On the other hand, the elongation and the reduction of area increased with increase of the aspect ratio of the prior beta grains; that means, increase of the deformation ratio. Raising of forging temperature also increased elongation and reduction of area due to the film-like GB alphaphase.

Highlights

The mechanical properties of Ti alloys for aero engines are highly influenced by their microstructure, which is controlled by thermo-mechanical processing, generally forging and heat treatment
The volume fraction of the primary alpha phase was determined by subtracting the volume fraction of grain boundary (GB) alpha phase from the sum of volume fraction of the primary and GB alpha phase obtained by electron backscatter diffraction (EBSD)
It was found that the volume fraction of GB alpha phase slightly increased at deformation ratio of 80%

Summary

Introduction

The mechanical properties of Ti alloys for aero engines are highly influenced by their microstructure, which is controlled by thermo-mechanical processing, generally forging and heat treatment. In the aviation industry, processing technology which can produce materials with desirable mechanical properties are strongly required. A plenty of researches have been performed to understand hot deformation behavior and the mechanism, and the microstructure evolution of Ti alloys, such as Ti-64, Ti6242, TIMETAL 834, Ti-17 and some of beta Ti alloys [for example 1-6]. Dynamic recovery and dynamic recrystallization are focused for thermo-mechanical processing in the beta phase field. Spheroidization or globularization of the alpha phase is focused for thermos-mechanical processing in the alpha + beta phase field. Various kinetics models to predict recrystallization have been proposed [1,2,3,4,5,6]

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Results

Conclusion