Orthogonal machining introduced microstructure modification in AA7150-T651 aluminium alloy

Bing Liu,Xiaorong Zhou,Xinxin Zhang

doi:10.1016/j.matchar.2016.11.015

Abstract

In the present work, orthogonal machining is simulated on AA7150-T651 aluminium alloy by cutting using ultramicrotomy. The simulation has successfully reproduced the interaction between the tool and the workpiece during industrial machining process and the associated shear deformation introduced to the workpiece. Within the tertiary shear zone, near-surface deformed layers, characterized by ultrafine grains with diameters less than 100nm, are generated on the workpiece. The thickness of the deformed layer ranges from approximately 200nm to 400nm, depending on the machining parameters. Increased cutting thickness or cutting speed results in the formation of a near-surface deformed layer with increased thickness. Machining with 0° clearance angle results in thicker deformed layer compared with that at 45° clearance angle.

Highlights

Extensive research on the microstructure evolution within the near-surface region where high shear deformation occurs during alloy fabrication or structure manufacturing processes, including rolling, mechanical grinding and polishing, has been reported recently [1,2,3,4,5,6,7,8,9]
It is evident that the characteristics of the near-surface deformed layer introduced by the industrial-scale machining process and the cutting process employed in the present work are the same, suggesting that the cutting process employed in the present work successfully simulated the interaction between the tool and the material beneath the tool during the industrial machining process and the associated deformation introduced to the workpiece
Orthogonal machining has been successfully simulated by ultramicrotomy which reproduces the interaction between the tool and the material beneath the tool during the industrial machining process and the associated deformation introduced to the workpiece

Summary

Introduction

Extensive research on the microstructure evolution within the near-surface region where high shear deformation occurs during alloy fabrication or structure manufacturing processes, including rolling, mechanical grinding and polishing, has been reported recently [1,2,3,4,5,6,7,8,9]. Near-surface deformed layers, exhibiting distinct microstructural features in comparison with the underlying bulk material, including the ultrafine equiaxed grains, redistribution of alloying elements and elements segregation at the grain boundaries, are formed on various metallic materials during the fabrication processes. Humphreys and Hatherly [13] proposed, based on the observation on materials undergoing high shear deformation processes, the dislocation network generated during severe deformation leads to the formation of sub-grain structures within the grain. Such structures with low-angle boundaries will become separate ultrafine grains as deformation progresses. The grain refinement process is referred to as continuous dynamic recrystallization

Methods

Results

Discussion

Conclusion