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Effect of process parameters on microstructure and mechanical properties of friction stir-welded Ti–6Al–4V joints

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An Erratum to this article was published on 11 May 2017

Abstract

In this work, the microstructure and mechanical behavior of friction stir-welded 2-mm-thick sheets of Ti–6Al–4V alloy were investigated. Specifically, the influence of friction stir welding (FSW) process parameters on microstructure evolution, defect generation, tensile, and hardness properties of the joint were studied. Optical and scanning electron microscopies were used to examine the microstructure and to determine the type and nature of the defects. A progressive change in the microstructure from equiaxed and elongated α grains (base metal) to a very fine lamellar structure with an average grain size of less than 1 μm (in the upper stir zone) was observed and related to FSW parameters. Tensile tests and microhardness measurements were also carried out to assess the mechanical properties. Important variations were observed on tensile strength and hardness distribution as a function of process parameters. The weakest mechanical properties and fracture were found in the heat-affected zone (HAZ) of the as-welded joints. The results were analyzed in terms of the pseudo heat index, and it was determined that tool rotation is the most significant process parameter influencing both the microstructure and mechanical properties of FSWed Ti–6Al–4V joints.

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Authors and Affiliations

  1. Ecole de Technologie Supérieure (E.T.S.), Département de Génie Mécanique, 1100 Rue Notre-Dame Ouest, Montréal, QC, H3C 1K3, Canada

    A. Fall & M. Jahazi

  2. Science and Research Branch, Islamic Azad University, Teheran, Hesarak, Iran

    A. R. Khdabandeh & M. H. Fesharaki

Authors
  1. A. Fall
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  2. M. Jahazi
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  3. A. R. Khdabandeh
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  4. M. H. Fesharaki
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Corresponding author

Correspondence to A. Fall.

Additional information

The original version of this article was revised: This article originally published with the author family name incorrectly listed. The author name have now been appear correctly above.

Submitting highlights

Ti–6Al–4V plates with a thickness of 2 mm were successfully friction stir welded under different welding conditions. The mechanical properties of the joint were investigated by using tensile test and microhardness measurements for different welding heat index parameters.

The following conclusions can be drawn from this study:

1. The heterogeneous distributions of mechanical properties were directly related to the microstructure. It was shown that the SZ has the highest mechanical properties while the HAZ is the weakest region in the weld. The mechanical properties of the HAZ can be associated with the transverse tensile properties of the weld.

2. Mechanical properties of the FSW joint were correlated with the change in the microstructure, mainly in grain size distribution. In addition, the β → α + β phase transition in titanium alloys strongly influences microstructure evolution and therefore affects the mechanical properties of the joint.

3. The heat index ratio can be used as a reliable parameter to describe the variations in strength and ductility of the joint.

4. The combined influence of temperature and strain, rather than temperature alone, is the key factor affecting the mechanical properties of the joint. Therefore, the tool rotational speed and the tool travel speed should be properly controlled to ensure good mechanical properties in FSWed Ti–6Al–4V alloys.

An erratum to this article is available at http://dx.doi.org/10.1007/s00170-017-0519-3.

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Fall, A., Jahazi, M., Khdabandeh, A.R. et al. Effect of process parameters on microstructure and mechanical properties of friction stir-welded Ti–6Al–4V joints. Int J Adv Manuf Technol 91, 2919–2931 (2017). https://doi.org/10.1007/s00170-016-9527-y

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  • DOI: https://doi.org/10.1007/s00170-016-9527-y

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