A multi-response optimization of the multi-directional forging process for aluminium 7075 alloy using grey-based taguchi method

C Obara,J N Keraita,H Shagwira,F M Mwema,J O Obiko

doi:10.1007/s42452-021-04527-2

C Obara, J N Keraita + Show 3 more

Open Access

https://doi.org/10.1007/s42452-021-04527-2

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Abstract

The multi-directional forging process of aluminium alloy 7075 (AA 7075) is studied using Deform 3D Version 11.0 simulation software. This process results in grain refinement in the bulk material. The 7075 aluminium alloy is used widely in the aerospace and automobile industries. Thermomechanical processing affects the mechanical properties of this alloy. This study focuses on optimising process parameters that affect the multi-directional forging using simulation. In the Taguchi design of experiment, four-factors and five levels are selected. The process input parameters considered are temperature, the strain per pass, the plunger speed, and the friction coefficient (μ). From Taguchi’s orthogonal array, forging simulations are undertaken and analysed. The significance of the process output parameters: material damage, stress and strain are analysed by analysis of variance. The results show that the friction coefficient and strain per pass highly affect the stress/strain distribution. Grey relational analysis is adopted to determine the optimum process parameters. The results show that the optimal combination of parameters is: temperature (200 °C), plunger speed (5 mm/s), friction coefficient (0.6), and strain per pass (0.6). Confirmation of simulation is carried out using the optimum input parameters. From the simulation results, the grey relational grade's optimal parameters have the highest maximum effective strain of 5.57, maximum effective stress of 665 MPa, and maximum damage of 0.416 compared to other simulated results.

Highlights

Multi-directional forging (MDF) is an important severe plastic deformation (SPD) process used in the grains refinement of metals and their alloys [1]
The process is cheap and easy to carry out because it does not need complex equipment when compared to other SPD processes, such as high-pressure torsion (HPT) and accumulative roll bonding (ARB) [2]
Effective stress is directly related to plastic deformation and higher effective stress is desirable during deformation

Summary

Introduction

Multi-directional forging (MDF) is an important severe plastic deformation (SPD) process used in the grains refinement of metals and their alloys [1]. The process is cheap and easy to carry out because it does not need complex equipment when compared to other SPD processes, such as high-pressure torsion (HPT) and accumulative roll bonding (ARB) [2]. It is capable of forging large samples. In the MDF process, materials are subjected to very high strains without necessarily resulting in dimensional changes to the samples. The compression results in a decrease in grain sizes and improved mechanical properties [3]. Noda et al reported that superplastic behaviour improved due to accumulated redundant plastic deformation [4]

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