The Influence of Ni and V Trace Elements on High-Temperature Tensile Properties and Aging of A356 Aluminum Foundry Alloy

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 47; no. 5; pp. 2049 - 2057
• Main Authors: Di Giovanni, Maria Teresa, Cerri, Emanuela, Casari, Daniele, Merlin, MATTIA, Arnberg, LARS, Garagnani, Gian Luca
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.05.2016; Springer Nature B.V
• Subjects: Aging (artificial); Aluminum alloys; Aluminum base alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Hardness; Materials Science; Metallic Materials; Metallurgy; Nanotechnology; Nickel; Permanent mold casting; Physical metallurgy; Sand; Structural Materials; Surfaces and Interfaces; Temperature; Tensile properties; Tensile strength; Thin Films; Trace elements; Ultimate Tensile Stress; Mg2Si Particle; Permanent Mold; Sand Cast; Permanent Mold Casting
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-016-3366-1

High-temperature tensile properties of unmodified A356 alloy with and without the addition of Ni or V in traces (600 and 1000 ppm of Ni and V, respectively) were investigated by analyzing samples obtained from sand and permanent mold castings in the as-cast and T6 heat-treated conditions. Tensile tests were performed at 508 K (235 °C) at a crosshead speed of 1 mm/min. In addition, samples were subjected to artificial aging at 508 K (235 °C) for different times, and corresponding hardness curves were plotted. Microstructures and fracture surfaces, analyzed by FEG-SEM equipped with energy dispersive X-ray spectroscopy, showed that neither Ni nor V addition had a detrimental effect on high-temperature tensile properties. Aging curves showed a strong loss of hardness affecting the T6 class between 30-min and 1-h exposure time. After 6-h aging, no evidence of aging treatment persisted on hardness of the tested material. Hardness values did not reveal any significant difference between the reference alloy and the Ni- and V-containing alloys in both casting conditions, in complete analogy with the tensile properties. Unmodified eutectic silicon particles provided inhomogeneity in the α -Al matrix and acted as the principal source of stress concentration leading to fracture.