1. Introduction

2. Materials and Methods

2.1. Manufacturing

The evaluated samples were manufactured in an LPBF process on a Trumpf TruePrint 1000 from AlSi7Mg0.6 aluminium alloy powder. Specifications of geometries and manufacturing settings are given subsequently.

Figure 1. Top view: sample orientation w.r.t. coater (top left), example of build job layout (bottom left), individual tested sample (middle) and finished build job on platform (right).

Figure 1. Top view: sample orientation w.r.t. coater (top left), example of build job layout (bottom left), individual tested sample (middle) and finished build job on platform (right).

Figure 2. Exposure strategy for bulk and contour scan: Bulk scan direction is rotated by ${66}^{\circ }$ (schematic representation, not true to scale) after each powder layer application.

Figure 2. Exposure strategy for bulk and contour scan: Bulk scan direction is rotated by ${66}^{\circ }$ (schematic representation, not true to scale) after each powder layer application.

2.1.1. Sample Geometry

There were two kinds of samples used in this work: Cuboids (height 10 mm, width 10 mm, thickness 5 mm) and fatigue specimens according to ASTM 466-15 [5] (height 80 mm, smallest cross section 6 mm, thickness 3mm). The latter type is shown in Figure 1.

2.1.2. Manufacturing Parameters

Table 1 and Table 2 as well as Figure 1 and Figure 2 contain detailed information on the manufacturing process.

Powder layers were exposed to the laser by a pattern of parallel stripes in the bulk, changing direction by ${66}^{\circ }$ after each layer, and a continous scan of the geometric contour. Sky writing was applied to ensure the laser source was moving at the chosen speed prior to exposure.

The samples were placed on the build platform at a ${45}^{\circ }$ angle w.r.t. coater and gas flow, as shown in Figure 1. Bulk scan parameters were identical for all samples, as specified in Table 1 and originate from a previous density optimisation study.

The contour scan parameters were varied, intending to achieve a variation of surface properties. Maintaining layer thickness, hatch distance and laser power, the scan speed was modified between 300 mm/s and 1800 mm/s, paired with the settings with and without additional pre-sinter at 50% laser power, resulting in a total of ten manufacturing parameter combinations.

The samples with identical parameter combinations were named by a designated letter according to Table 3 with consecutive numbering, e.g.: A1 → Contour parameter set A (scan speed 300 mm/s, with pre-sinter), mechanical testing sample No. 1.

2.3. Workflow Summary

Figure 3 gives a summary of this work’s process steps.

At the first manufacturing stage, 30 cuboid samples were made. All of these were made with identical bulk scan parameters, paired with 10 variations of contour scan parameters, resulting in 3 cuboid samples per parameter set combination.

Table 3. Naming of sample groups based on contour scan variation.

Table 3. Naming of sample groups based on contour scan variation.

Scan Speed in mm/s	300	600	900	1200	1800
Pre-sinter	A	C	E	G	I
No Pre-sinter	B	D	F	H	J

Afterwards, the cuboids’ densities and surfaces were measured in order to get a first assessment of bulk quality on one hand and rating based on the surface quality on the other hand. Based on these evaluations, parameter sets were chosen to produce samples for mechanical testing. Details on the selection process can be found in Section 3.2.

For seven manufacturing parameter sets chosen based on the cuboid assessment, six samples each were made for mechanical testing.

As a final part of this work, tensile testing according ASTM E8M [9] was performed.

In subsequent studies, fatigue performance was investigated for a selection of the manufacturing parameter sets. A part of these studies is already published [10].

3. Results and Discussion

4. Summary and Future Work

Abbreviations

References

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