Issue 68

S. Cecchel et alii, Frattura ed Integrità Strutturale, 68 (2024) 109-126; DOI: 10.3221/IGF-ESIS.68.07

Figure 7: Optical microstructure of LPBF 17-4PH solutioned for both samples (flat and cylindrical) and component sections at different magnifications. Fig. 8 reported SEM images on flat samples both in as-built and solutioned state. Similar considerations can be extended to cylindrical samples, as can be observed from the analyses reported in the supplementary material section (fig. 15). SEM investigations confirmed that the as-built microstructure is expected to be composed of large columnar δ -ferrite grains, small island of martensite and retained austenite. After the solution treatment, it can be noted the presence of martensite with some islands of primary austenite. The grains size increased for all the constituents due to high temperature exposure that leads to recrystallization and faster grain growth. It can be noted from EDS analysis a difference of Cu content between martensite and the matrix after solubilization. In particular in elemental mapping analyses in Fig. 9 are visible a large number of ε -Cu precipitates particularly concentrated along the martensite lath. Also these analyses confirmed the previous comments gathered from OM.

Figure 8 : SEM images and EDS analysis of LPBF 17-4PH as built and solutioned for flat samples.

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