Creep properties and microstructure evolution at 260–300 °C of AlSi10Mg manufactured via laser powder-bed fusion

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-05, Vol.843, p.143075, Article 143075
• Main Authors: Glerum, Jennifer A., Mogonye, Jon-Erik, Dunand, David C.
• Format: Article
• Language: English
• Subjects: Activation energy; Additive manufacturing; Aluminum; Aluminum base alloys; Casting alloys; Coarsening; Creep; Creep strength; Filaments; Laser powder-bed fusion; Load transfer; Magnesium base alloys; Mechanical properties; Powder beds; Power law; Silicon; Threshold stress; Zirconium
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.143075

The aging behavior and creep resistance of eutectic AlSi10Mg (Al–10Si-0.6Mg, wt.%) manufactured by laser powder bed fusion (L-PBF) are studied at 260 and 300 °C. The Si phase, which forms a fine interconnected network of 100–200 nm filaments in the as-printed alloy, coarsens into blocky, 2–3 μm particles after 1 month exposure at 260 and 300 °C, with hardness decreasing following a power-law with exponent n = 0.06–0.08. AlSi10Mg with ∼1 μm Si particles (achieved by aging at 300 °C for 96 h) exhibits creep resistance at 260 and 300 °C, for test durations of a few days, comparable to those of (i) cast alloys: hypereutectic Al–Si alloys with coarse Si particles and eutectic Al–Ce, Al–Ce–Ni with much finer, and more coarsening-resistant eutectics phases (e.g., Al11Ce3, Al3Ni); and (ii) L-PBF Al–Mg–Zr alloys. At 260 and 300 °C, our L-PBF AlSi10Mg shows a power-law creep behavior with high apparent stress exponents (na = 10–13, higher than n = 4.0 for Al–Mg) for strain rates between ∼10−8 and ∼10−4 s−1. Also, a high apparent creep activation energy Qa = 256 kJ/mol is measured between 200 and 320 °C at 45 MPa, compared to Q = 142 kJ/mol for Al. These high apparent stress exponent and activation energy are consistent with power-law dislocation creep with a threshold stress, originating from load-transfer from the creeping Al(Mg) matrix to non-creeping Si particles.