Bulk fracture anisotropy in Cold-Sprayed Al 6061 deposits

• Published in: Engineering fracture mechanics 2022-03, Vol.263, p.108301, Article 108301
• Main Authors: Julien, Scott E., Nourian-Avval, Ahmad, Liang, Wentao, Schwartz, Tricia, Ozdemir, Ozan C., Müftü, Sinan
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Aluminum base alloys; Anisotropy; Bulk modulus; Cold spray; Cold spraying; Crack propagation; Elastic properties; Elongation; Fracture toughness; Heat treating; Helium; Low level; Mechanical properties; Modulus of elasticity; Tensile properties; Tensile strength
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2022.108301

•Fracture toughness anisotropy was studied in bulk helium-sprayed aluminum 6061 cold spray deposits.•ASTM E399 was used to measure toughness in six principal crack/load orientation configurations.•Resulting toughness was transversely orthotropic, with higher values when fracture occurred through the deposit thickness.•Fracture was both transparticular (through particles) and interparticular (along particle interfaces).•A greater amount of transparticular fracture was observed in orientations with higher toughness. Tensile and fracture anisotropy were studied in helium-sprayed bulk Al 6061 cold spray deposits. Tensile properties (elastic modulus, yield strength, tensile strength, and elongation at break) were measured in the two in-plane principal deposit directions (long-rastering, and stepping), and fracture toughness was characterized for six principal load/crack direction pairs defined with respect to the spray directions. No in-plane anisotropy was measured for the tensile properties, attributed to uniform in-plane microstructure. Fracture toughness was found to be mildly transversely isotropic, with equal values when crack propagation was in-plane (mean of 11.0 MPa√m) and slightly higher values when crack propagation was out-of-plane (through the deposit thickness, mean of 13.0 MPa√m). The overall fracture toughness range was 40–50% that of wrought Al 6061-T6. In-plane fracture was almost completely interparticular (fracture along particle interfaces), while out-of-plane fracture was a mixture of interparticular and transparticular (fracture through particles). A greater amount of transparticular fracture was observed in orientations with higher toughness. Overall, the low level of anisotropy was attributed to good interparticle bonding as a result of effective spray parameters and the use of helium as the accelerating gas.