Phenomenological Constitutive Models for Hot Deformation Behavior of Ti6Al4V Alloy Manufactured by Directed Energy Deposition Laser

Yong Niu,Yaoqi Wang,Zhonggang Sun,Jiawei Niu

doi:10.3390/met10111496

Abstract

This work focuses on the hot deformation behavior and constitutive models of Ti6Al4V alloy manufactured by directed energy deposition laser (DEDL). The hot compression tests of DEDL Ti6Al4V alloy at deformation temperature of 700–950 °C and strain rate range of 0.001–1 s−1 were carried out. Three phenomenological models including modified Johnson–Cook model, modified Fields–Backofen model, and strain-compensated Arrhenius model were introduced to predict the flow stresses during uniaxial compression. The predictability of the three models is evaluated according to correlation coefficient, average absolute relative error, and average root mean square error. Traditional linear regression method (TLRM) and nonlinear regression analysis (NRA) were used to solve the constants of modified Johnson–Cook model and strain-compensated Arrhenius model, NRA was used to solve the constants of modified Fields–Backofen model. Compared with the TLRM, the NRA improves the accuracy of modified Johnson-Cook model, while has limited effect on that of strain-compensated Arrhenius model. The accuracy of modified Fields–Backofen model and strain-compensated Arrhenius model is higher than that of modified Johnson–Cook model.

Highlights

Metal additive manufacturing technology has the advantages of short cycle, high material utilization, fast forming, and free design
It is difficult to avoid the formation of coarse columnar crystal structure in additive manufacturing parts [1]
By forging additive manufacturing preforms, the porosity can be eliminated, the microstructure refined, and the grain flow pattern induced, so that the components can be strengthened under fatigue load [2,3,4,5]

Summary

Introduction

Metal additive manufacturing technology has the advantages of short cycle, high material utilization, fast forming, and free design. It still has a long way to go in the application. Ti6Al4V is widely used in airframe and aero-engine. It is difficult to avoid the formation of coarse columnar crystal structure in additive manufacturing parts [1]. By forging additive manufacturing preforms, the porosity can be eliminated, the microstructure refined, and the grain flow pattern induced, so that the components can be strengthened under fatigue load [2,3,4,5]. In order to give full play to the potential of hybrid manufacturing, it is important for designers to understand the flow characteristics of additive manufacturing preformed parts during thermal forming

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Conclusion