PSI - Issue 24

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

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Paolo Folgarait et al./ Structural Integrity Procedia 00 (2019) 000 – 000

Fig. 9 . Reduction of Area (ROA%) for 0 group ( as-built condition). No min value supplied by EOS.

All measured mechanical quantities are greater (or not lower) than the reference values supplied by EOS in the alloy datasheet (see Table 5) and equivalent to present B1 group (see Fig. 10 to 13 ). With respect to this heat treatment (same temperature, much longer holding time, 4 time the actual) both UTS h and YS h are closer to typical minimum values declared by EOS for the B1 case. The same behavior is for El% h . A possible explanation may be found in an uncomplete precipitation of fine particles of impurity phases (second phase particles), whose change in solid solubility with temperature (and time) is responsible for impeding the movement of dislocations, mechanism affecting both UTS and YS, as well as deformation parameters (El% mainly). The reason why this effect assumes a stronger relevance in horizontally oriented specimens should be searched in the different thermal history experienced by these samples during printing respect to vertically oriented ones, and consequently the different solidification microstructure and initial impurities distribution in the as-built microstructure. Also not completely removed residual stresses in the horizontally fabricated samples may contribute to justify imparities. This difference made more effective due to the absence of a solution annealing treatment before ageing (as typically applied in hot rolled or forged components) and equivalent to current A2 group (Table 2).

Fig. 10 . Ultimate Tensile Strength (UTS) for A1 group (STANDARD). Min value as per EOS reference (Table 5), equivalent to B1 (Table 2).