Effect of multi-directional hot forging process on the microstructure and mechanical properties of Al–Si based alloy containing high amount of Zn and Cu

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2021-01, Vol.803, p.140709, Article 140709
• Main Authors: Alemdag, Yasin, Karabiyik, Sadun, Mikhaylovskaya, Anastasia V., Kishchik, Mikhail S., Purcek, Gencaga
• Format: Article
• Language: English
• Subjects: Aluminum; Al–Si–Zn–Cu alloys; Copper; Crystallization; Ductile fracture; Ductile-brittle transition; Grain boundaries; Hardness tests; Hot forging; Hydraulic presses; Mechanical properties; Microstructure; Multi-directional forging; Optical properties; Precipitates; Precipitation hardening; Severe plastic deformation; Silicon base alloys; Tensile properties
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2020.140709

In this study, the hypoeutectic Al–7Si based alloy containing Zn and Cu was severely deformed with multi-directional forging (MDF) process at 200 °C. The samples were placed into an open die allowing the free deformation in only one direction and forged with hydraulic press at cumulative strains of 2.07, 4.14 and 6.21. The microstructural examinations were performed with X-ray diffractometer, optical, scanning and transmission electron microscopies while their strength properties were determined by tensile and hardness tests. MDF led to a refinement in α-Al grains, hard Si, Al7Cu2Fe and Al2Cu particles of crystallization origin. This process also provided a method for formation of secondary precipitates within the alloy's microstructure. It was determined that MDF increased the tensile properties of the alloy but decreased its hardness. On the other hand, this process converted brittle type fracture of homogenized alloy to ductile type. These results were explained in terms of grain boundary strengthening, precipitation hardening, refining of hard particles, and softening in matrix due to dynamic recovery and recrystallization mechanisms. •The Al–7Si alloy containing Zn and Cu is successfully processed with MDF at 200 °C.•MDF results in broken up hard particles and grain refinement of α-Al matrix.•MDF cause to a significant increase in yield strength and ductility of the alloy.•Results is explained in terms of strengthening and softening mechanisms.