Forming and properties of 7075 aluminum alloy by rheological squeeze casting with transverse mobile injection feed

• Published in: International journal of advanced manufacturing technology Vol. 119; no. 11-12; pp. 7969 - 7981
• Main Authors: Pei, Huan-Wei, Zhang, Shu-Guo, Guo, Hong-Min, He, Wen, Liu, Xu-Bo
• Format: Journal Article
• Language: English
• Published: London Springer London 01.04.2022; Springer Nature B.V
• Subjects: Aluminum alloys; Aluminum base alloys; CAE) and Design; Casting; Casting alloys; Coalescing; Computer-Aided Engineering (CAD; Crystal defects; Dimpling; Elongation; Engineering; Fracture surfaces; Grain size; Industrial and Production Engineering; Mechanical Engineering; Mechanical properties; Media Management; Original Article; Rheological properties; Rheology; Semisolids; Slurries; Solution heat treatment; Squeeze casting; Ultimate tensile strength; Voids; Wrought aluminum alloy; Mechanical properties; Microstructure; Tensile fracture; Rheoforming
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-022-08750-y

Mechanical properties and tensile fracture behavior of normal 7075 aluminum alloy produced by rheoforming were investigated. The rheoforming applies limited angular oscillation (LAO) technique for semi-solid slurry preparation and rheological squeeze casting with transverse moving injection feed semi-solid slurry. The microstructures of as-cast rheoformed 7075 alloy are composed of fine spherical α-Al grains with average size of 26 μm surrounded by eutectic mixture. T6 heat treatment (solution treatment for 4 h at 838 K (465 °C) and aging for 12 h at 393 K (120 °C)) causes a slight increase of grain size and the formation of fine semi-coherent precipitation of η′ phase in α-Al matrix. Good elongation to fracture (10.1%, which is quite close to the wrought target (11%)) is obtained for rheoformed 7075 alloy after T6 heat treatment, with average yield strength of 461 MPa and average ultimate tensile strength of 514 MPa. Pores and voids are main defects observed in rheoformed 7075 alloy. The fracture surface of as-cast rheoformed 7075 alloy consists of large and deep dimples showing the growth and coalescence of voids. After T6 treatment, the fracture surface is composed of large dimples, flat areas containing super-fine dimples and tear ridges. Pores are present in the form of large dimples in fracture surface. The crack initiates at pores and propagates by the coalescence of pores and voids.