Elsevier

Journal of Manufacturing Processes

Volume 73, January 2022, Pages 207-219
Journal of Manufacturing Processes

Decisive influence of critical process parameters on the microstructure and tensile properties of friction stir back extruded magnesium alloy tubes

https://doi.org/10.1016/j.jmapro.2021.11.013Get rights and content

Abstract

Friction Stir Back Extrusion (FSBE) is evolving as a novel extrusion process for producing high strength ultrafine-grained tubes from a range of metallic alloys. This investigation focuses on developing a high-fidelity experimental methodology to control the critical process parameters of the FSBE process for manufacturing high strength ZE41 magnesium alloy tubes. The crucial parameters of FSBE required to manufacture highly reliable ZE41 tubes were determined with solid evidence obtained through a wide range of thorough experimental trials on ZE41 magnesium round rods. The metallurgical characterisation was performed at key regions across the tubes obtained using the ideal process conditions to understand the influence of FSBE process parameters on the microstructural formation. Mechanical properties of the tubes were evaluated and found that the tubes produced at optimum conditions have achieved high tensile and hoop strengths. The microstructure-mechanical property correlation confirmed that the FSBE process driven with the controlled process parameters enable to produce defect-free high strength ZE41 magnesium tubes with a significant enhancement in grain refinement.

Section snippets

Nomenclature/abbreviations

SymbolProperties/parametersUnit
LTSFSBETensile strength in the longitudinal directionMPa
HTSFSBETensile strength in the hoop directionMPa
YSYield strength of the base metalMPa
TSTensile strength of the base metalMPa
PEPercentage elongation%
NTool rotational raterpm.
FAxial tool feedmm/min
TDwell times.
TpDeformation temperatureo C
davgaverage grain sizeμm
ε̇strain rates−1
RaAverage material movementrps
rActive radius of the dynamically recrystallised zonemm
hActive depth of the dynamically

FSBE magnesium alloy billet preparation

As-casted magnesium ZE41 alloy plate was sliced and machined into a cylindrical rod with 22 mm diameter and 200 mm length with a rectangular base of 30 × 25 × 10 mm. The base avoids the billet rotation with the plunger during the FSBE process. The H13 steel plunger was machined to 18 mm diameter so that an annular space of 2 mm was available between the plunger and the inner diameter of the FSBE die. As schematically represented in Fig. 1, this setup ensures the final production of magnesium

Effects of poor process parameters selection

The FSBE process with the tool rotational rate less than 1250 rpm led to the formation of cracks on the tube surface in line with the tube circumference (Fig. 3a), presumably due to poor deformation characteristics of the material. Similarly, the FSBE process attempted with the tool rotation rate greater than 2250 rpm has led to non-uniform deformation due to the severe turbulence caused by the higher tool rotation rates. In addition to this, the higher tool rotation rates also caused a

Conclusions

In this paper, the effect of FSBE process parameters on the microstructure and mechanical properties of Mg tubes was investigated. The following conclusions can be drawn based on the results and observations achieved by this study:

  • FSBE process was used to produce Mg tubes with superior mechanical strength by carefully selecting crucial FSBE process parameters such as tool rotation rate, dwell time, and tool feed rate. It was confirmed that the tool rotational speed has a major impact on the

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (40)

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