Effect of Industrial Heat Treatment and Barrel Finishing on the Mechanical Performance of Ti6Al4V Processed by Selective Laser Melting

Filippo Nalli,Luana Bottini,Luca Cortese,Francesco Veniali,Alberto Boschetto

doi:10.3390/app10072280

Filippo Nalli, Luana Bottini + Show 3 more

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https://doi.org/10.3390/app10072280

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Abstract

Additive manufacturing is now capable of delivering high-quality, complex-shaped metallic components. The titanium alloy Ti6Al4V is an example of a printable metal being broadly used for advanced structural applications. A sound characterization of static mechanical properties of additively manufactured material is crucial for its proper application, and here specifically for Ti6Al4V. This includes a complete understanding of the influence of postprocess treatment on the material behavior, which has not been reached yet. In the present paper, the postprocess effects of surface finish and heat treatment on the mechanical performance of Ti6Al4V after selective laser melting were investigated. Some samples were subjected to barrel finishing at two different intensities, while different sets of specimens underwent several thermal cycles. As a reference, a control group of specimens was included, which did not undergo any postprocessing. The treatments were selected to be effective and easy to perform, being suitable for real industrial applications. Tensile tests were performed on all the samples, to obtain yield stress, ultimate tensile strength and elongation at fracture. The area reduction of the barrel-finished samples, after being tested, was measured by using a 3D scanner, as a further indication of ductility. Experimental results are reported and discussed, highlighting the effect of postprocessing treatments on the mechanical response. We then propose the optimal postprocessing procedure to enhance ductility without compromising strength, for structures manufactured from Ti6Al4V with selective laser melting.

Highlights

Additive manufacturing (AM) technologies are becoming widespread thanks to their promising ability to manufacture nearly any complex shape
The present study aims to quantify the improvements on the static mechanical properties of selective laser melting (SLM)
The barrel‐finished samples exhibited a maximum scatter below 15% in terms of yielding stress, while the thermal‐treated specimens showed an improved behavior in terms of repeatability, with the only exception being the samples treated at 482 °C (TT 482), with a significantly higher yielding value

Summary

Introduction

Additive manufacturing (AM) technologies are becoming widespread thanks to their promising ability to manufacture nearly any complex shape. There is a large number of AM methods for metal [1], and such methods can be categorized largely into two groups [2]: Directed Energy Deposition and Powder Bed Fusion The former is characterized by large process complexity and requires a careful design of the part in order to obtain complex shapes with satisfactory accuracy, putting the Directed Energy Deposition at a great disadvantage with respect to powder bed methods. Within the latter category, selective laser melting (SLM), known as direct metal laser sintering (DMLS), deposited by EOS, has the ability to produce highly complex-shaped components with relative ease.

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