PSI - Issue 42

Aditya Pandey et al. / Procedia Structural Integrity 42 (2022) 1017–1024 Pandey et al. / Structural Integrity Procedia 00 (2019) 000–000

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2.4. Characterization

A simple cube of size 10 mm was manufactured on a flat substrate for the metallographic observation. Melt pool characterization was done using optical microscope. The printed sample for metallographic observation was prepared with standard polishing procedures and then etched with 1.3 ml 30% H 2 O 2 , and HCL 10 ml solution for 4 second (Deng et al. (2018)). Additionally, the fracture surface morphology of broken samples was examined using FE-SEM to study the associated damage mechanisms for crack initiation and propagation.

2.5. Finite element analysis

A three-dimensional finite element heat transfer model was developed to simulate the SLM process (Lee et al. (2016);Zhang et al. (2021)). The model was used to investigate the e ff ect of laser material interaction of a single layer multi-track laser melting process on a thick powder bed of IN718 alloy. The simulated results (i.e. melt pool depth, width and hatch spacing) then analyzed and validated with experimental results.

3. Results and discussion

3.1. Monotonic loading behavior

The measured mechanical properties of the as-built and heat-treated samples are listed in page 4 and the curves are shown in Figure 4. The results demonstrate that the heat-treatment dramatically improved the yield and the ultimate strength while significantly reducing the elongation. The comparatively lower strength in the as-built condition can be due to the lack of γ ’ and γ ” phase precipitates which would emerge during the heat treatment process (Schneider et al. (2018)).

Table 3. Tensile properties for di ff erent material conditions Property

As-Built

Heat-Treated 171.5 ± 3.57

Elastic Modulus (GPa) Yield Strength (MPa)

179.2 ± 6.68

680.18 ± 12.0 963.35 ± 117.00 Ultimate Strength (MPa) 970.25 ± 11.25 1195.22 ± 85.00 Elongation (%) 31.62 ± 0.30 15.81 ± 0.07

Fig. 4. Tensile test results for as-build and heat-treated samples at room temperature