Portal de Periódicos da CAPES

Structural analysis of heat treated automotive cast alloy

2011; Index Copernicus International S.A.; Volume: 47; Linguagem: Inglês

2300-892X

Eva Tillová, Mária Chalupová, L. Hurtalová, M. Bonek, L. A. Dobrzański,

Additive Manufacturing and 3D Printing Technologies

Purpose: The present study is conducted to investigate and to provide a better understanding of the heat treatment T4 (solution treatment at 505, 515 and 525°C, holding time 2, 4, 8,16 and 32 hours, then quenching in warm water in the range from 40°C and natural aging at room temperature during 24 hours) on the microstructure (morphology of eutectic Si, morphology of intermetallic Feand Cu-rich phases) and on mechanical properties (tensile strength and Brinell hardness) of recycled (secondary) AlSi9Cu3 cast alloy. Design/methodology/approach: Metallographic samples were selected from tensile specimens (after testing) and prepared by standard metallographic procedures (wet ground, polished with diamond pastes, finally polished with commercial fine silica slurry (STRUERS OP-U) and etched by Dix-Keller, HNO3 or H2SO4 (standard etching) or HCl (deep etching in order to reveal the three-dimensional morphology of phases). The microstructure was studied using an optical microscope Neophot 32 and SEM observation with EDX analysis using scanning electron microscope VEGA LMU II linked to the energy dispersive X-ray spectroscopy (EDX analyser Brucker Quantax). Hardness measurement was performed by a Brinell hardness tester with a load of 62.5 kp (1 kp = 9.807 N), 2.5 mm diameter ball and a dwell time of 15 s. Findings: The results indicate that increasing solution treatment temperature results in spheroidization of eutectic Si, gradual disintegration of iron rich intermetallic phases on base Al15(FeMn)3Si2, dissolution but also melting of intermetallic phases on base Al-Al2Cu-Si. Optimal solution treatment (515°C/4 hours) most improves mechanical properties. Further increases of solution time, leads to alloy elongations, while both, the tensile strength continuously drop. Practical implications: The present study is a part of larger research project, which was conducted to investigate and to provide a better understanding microstructure, heat treatment and mechanical properties of recycled (secondary) Al-Si cast alloy. Originality/value: The paper contributes to better understanding effect of the T4 heat treatment on the microstructure (morphology of eutectic silicon and intermetallic phases) and mechanical properties (tensile strength and Brinell hardness) of recycled cast alloy.