PSI - Issue 24

Jacopo De Nisi et al. / Procedia Structural Integrity 24 (2019) 541–558 Paolo Folgarait et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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3. Experimental results

3.1. Microstructural features The 15 – 5PH alloy exhibits good short transverse ductility and a reasonably high strength in large section sizes when used in either annealed or over-aged condition and is normally heat treated after fabrication. Two different heat treatments involving precipitates can alter the strength of a material: solution heat treatment and precipitation heat treatment. Solid solution strengthening involves formation of a single-phase solid solution via (oil) quenching or accelerated cooling. Precipitation heat treatment involves the addition of impurity particles to increase a material's strength. Precipitation hardening via precipitation heat treatment is the main topic of discussion in this paper. Metallographic samples have been prepared from 3D printed specimens, according to ASTM E3-11 Standard, after proper section. The preparation included preliminary grinding operations using silicon carbide sandpapers, progressively increasingly finer, till 1000 grit. The polishing operation has followed, using oxides, till to reach a finishing roughness Ra=1.0 micron or below ( lapping ). Metallographic acid attack according to ASTM E407 07(2015)e1 Standard, using the Vilella reagent. Micrographs at x500 are reported in Table 3 , for all groups and positions A, E and I (quadrant Q1, Q5 and Q9).

Table 3 . x500 (50 micron) metallographic sections, Vilella etched. Beneath upper growth surface.

Group/Locatio n

Q1 (A)

Q5 (E)

Q9 (I)

As-built condition

A1

A2