Effect of varying TiB2 reinforcement and its ageing behaviour on tensile and hardness properties of in-situ Al-4.5%Cu-xTiB2 composite

• Published in: Journal of alloys and compounds 2019-07, Vol.793, p.454-466
• Main Authors: Mozammil, Shaik, Karloopia, Jimmy, Verma, Raviraj, Jha, P.K.
• Format: Article
• Language: English
• Subjects: Aging; Aging (artificial); Aluminum base alloys; Aluminum matrix composites; Boron; Copper; DSC; Electron probes; EPMA; Evolution; Exothermic reactions; Field emission microscopy; Heat treatment; HR-TEM; In-situ Al-4.5%Cu-TiB2 composite; Mechanical behaviour; Mechanical properties; Microscopy; Microstructure; Reaction kinetics; Scanning electron microscopy; Stir casting; Titanium diboride; Transmission electron microscopy; Water quenching; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.04.137

The objective of this study is to understand the suitability of mixed salt route using stir casting technique to fabricate in-situ Al-4.5%Cu-xTiB2 (x = 3, 6, 9 and 12 wt %) composites. The mechanism behind titanium/boron-based phase evolution in Al-Cu alloy has been enlightened first time, particularly its strong influence over mechanical behaviour was examined. The in-situ TiB2 reinforcement particles were prepared by the exothermic reaction of K2TiF6 and KBF4 salts in melted aluminium copper alloy which improves the hardness, yield, and tensile strengths to the extent of ∼89 VHN, ∼236 MPa and ∼295 MPa, respectively. Preliminary microstructural evolution was analysed and discussed through optical microstructures and proposed mechanism. The composites were characterized carefully with the help of field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) to know the morphological details and TiB2 distribution in the aluminium matrix composite (AMC) microstructure. In support with electron microscopic observations, the X-ray diffraction (XRD) and Electron Probe Microscopic Analysis (EPMA) were also performed. To further enhance the mechanical properties, T6 heat treatment (HT) was done. During the HT process, the composites were solutionized at 540 °C for two hours followed by water quenching. After that, artificial ageing was carried out at 170 °C with varying durations of 5, 10, 15, 20, and 25 h and post-ageing effect on the mechanical properties were recorded. Composites were thermally characterized through differential scanning calorimetry (DSC) to learn the precipitation kinetics and compared with alloy chosen. •Thermodynamics of TiB2 precipitation explained through Miedema model.•HR-TEM discerned the associated detailing of particle/matrix interface.•Intermetallic phases investigated through Electron Probe Micro Analysis.•Mechanism of TiB2 evolution and its correlation with tensile and hardness properties.