In situ detection of thermally induced porosity in additively manufactured and sintered objects
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Dilatation measurements, combined with thermal programmed desorption mass spectrometry (TPD-MS), were utilized for studying thermally induced porosity (TIP) in selective laser melting additively manufactured (AM) AlSi10Mg and Ta30at.%–Ti samples produced by hot isostatic pressing (HIP). A clear abrupt upward deviation in thermal expansion is observed, most probably indicating the occurrence of TIP mechanisms in both AM objects and powder metallurgy samples. For both AlSi10Mg and Ta30at.%–Ti, pores are clearly observed by either microscopic or macroscopic examinations. The TPD-MS analysis shows that both water and hydrogen evolve from AlSi10Mg powder particles, thus suggesting that thermally induced expansion of trapped hydrogen in HIP’ed Ta30at.%–Ti alloy and in laser powder bed fusion AlSi10Mg is the main source for the pressure increase in pores that consequently leads to permanent expansion upon heating. A simplified model that correlates the pressure inside the pores with the weakening of the material upon heating and TIP is proposed.
The authors thank Ms. Nataly Kosterya (NRCN) for running the TPD measurements and Mr. David Noyman (NRCN) for his technical assistance. Special thanks are extended to Dr. Ofer Tevet and Dr. Eitan Tiferet (NRCN) for helpful discussions. This study was undertaken under the auspice of Project #2022851 from the Israeli Ministry of Space and Technology.
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