Microstructure and properties of aluminum silicon/short fibre carbon composites fabricated by semi-solid thixomixing

• Published in: Materials & design Vol. 88; pp. 683 - 692
• Main Authors: Akbarzadeh, Ebrahim, Picas, Josep A., Teresa Baile, M.
• Format: Journal Article Publication
• Language: English
• Published: Elsevier Ltd 25.12.2015
• Subjects: A. Carbon fibers; A. Metal–matrix composites (MMCs); Adhesion; Aluminum base alloys; Assaig de materials; B. Fiber/matrix bond; Carbon fibers; Composite materials; Compostos metàl·lics; Design engineering; Dispersions; E. Thixomixing; Enginyeria dels materials; Fiber/matrix bond; Fibres de carboni; Intermetallics; Metallic composites; Metal–matrix composites (MMCs); Proves; Semi-solid processing; Silicon; Testing; Thixomixing; Wettability; Àrees temàtiques de la UPC; A. Carbon fibers; E. Thixomixing; B. Fiber/matrix bond; A. Metal–matrix composites (MMCs)
• ISSN: 0264-1275; 0261-3069; 1873-4197
• DOI: 10.1016/j.matdes.2015.09.015

A novel method was developed, based on thixotropic nature of semi-solid slurry of aluminum silicon alloy, for the effective dispersion and distribution of short carbon fibers (Csf) under intensive shear stress (τ) into the eutectic without physical or chemical damage. The Csf were distributed homogeneously into the matrix at optimum conditions: a temperature of 576–580°C, around 48% of solid fraction, and rotation speed of mixing was at 100rpm. The gas entrapment and porosity was a challenge in the fabrication the aluminum composite by thixomixing, and its size increased when the samples were heat treated. The extruded and heat treated composites had around 24% improvement of mechanical strength as assessed by tensile tests. The predominant deposition of silicon and its intermetallics at the interfacial region improved the wettability and adherence to achieve good mechanical properties. The formation of some intermetallics can be helpful to overcome low wettability effects and their structural evolutions were impressive. The fractography analysis illustrated the ductile fracture with some plastic deformation as the results of dimples and some fiber pull-out in the fractured surface. Ultra-micro hardness evaluation showed good interfacial bonding after heat treatment. The thixomixing process can be developed to produce various composites with different reinforcement. [Display omitted] •Thixomixing was developed for fabrication of Al/carbon fiber composite at semi-solid state.•Among Si, Mg and Fe, silicon is the first to form deposits.•Si improved wettability and interfacial adherence of homogeneously distributed fibers.•Heat treatment can modify the microstructure and promote mechanical properties.•Porosity is a challenge in this method and reduces the strength; pores become bigger when heat treated.