# Effect of Post-Printing Methods on the Microstructure and Mechanical Properties of Ti6Al4V Titanium Alloy Samples Fabricated Using Laser Powder Bed Fusion

## TL;DR

This paper studies how post-printing methods affect the microstructure and hardness of titanium alloy samples made with 3D printing.

## Contribution

The study reveals how different post-printing methods and temperatures influence microhardness and microstructure in Ti6Al4V alloy samples.

## Key findings

- Printing orientation significantly affects the effectiveness of HIP and heat treatment processes.
- Annealing promotes fine α-phase precipitation in the β phase, enhancing strength.
- Higher microhardness was observed in cross-sections perpendicular to the printing direction.

## Abstract

Laser powder bead fusion (LPBF) allows for the fabrication of highly accurate components from metal powders, which is difficult to achieve using traditional methods. LPBF-produced components can be characterized by their porosity and unfavorable microstructure, making further processing difficult. Therefore, appropriate post-printing methods are crucial, as they reduce porosity, reduce residual stresses, and stabilize the microstructure. The aim of this paper was to determine the effect of post-printing methods on the microhardness and microstructure of Ti6Al4V titanium alloy samples fabricated using the LPBF process in different orientations. Hot isostatic pressing (HIP) at various temperatures (910 °C, 1150 °C, 1250 °C), annealing at 1020 °C, and twist channel angular pressing using a 90° channel ending with a helical exit were considered postprocessing methods for LPBF-produced samples. Printing orientation significantly determined the effectiveness of HIP and the heat treatment processes. Higher microhardness was observed on the cross-section oriented perpendicular to the 3D printing direction. Annealing under appropriately selected conditions favors the precipitation of fine particles of the α phase in the β phase, leading to a strengthening effect by precipitation. Based on the microhardness measurements, clear differences were observed in the mean values, statistical ranges, and result distributions depending on the printing plane, HIP process parameters, and the use of an additional heat treatment. The HIP process leads to a more pronounced homogenization of microstructure and defect reduction, with the morphology of the microstructure and microhardness distribution dependent on the HIP process temperature.