Preparation and characterization of in-situ Al-Al X Ni Y composites via reactive infiltration Mohsen Rasouli a , Farshad Akhlaghi b , O.O. Ojo c , Moslem Paidar a, * a Department of Material Engineering, South Tehran Branch, Islamic Azad University, Tehran 1459853849, Iran b School of Metallurgy and Materials Engineering, University College of Engineering, University of Tehran,111554563 Tehran, Iran c Department of Industrial and Production Engineering, Federal University of Technology Akure, Nigeria article info Article history: Received 9 September 2018 Received in revised form 22 November 2018 Accepted 30 November 2018 Available online 1 December 2018 Keywords: Reactive infiltration In-situ Al 3 Ni Al 3 Ni 2 composite Microstructure Mechanical properties Fracture abstract In-situ Al-Al x Ni y composites were prepared by reactive infiltration method via reaction between a preform of 12 strands of commercially pure Ni wire (99%) having 150 mm diameter and molten commercially pure aluminum (99.6%), with a subsequent heat treatment. The microstructures and compositions, microhardness, tensile properties and fracture behaviors of the composites were analyzed and compared with that of pure Al and Al-1.92%Ni alloy. The results reveal that acid pickling effect enhances homogeneous infiltration and solid-state inter-diffusion into the Ni wires. Prolonged heat treatment time (300 min) promotes homogeneous solid-state inter-diffusion around the Ni core in the composite subjected to sub-eutectic heat treatment (625  C). The thickness of intermetallic compounds increases from 5.5 to 24.9 mm (for samples heated below eutectic point) and 550e1600 mm (for samples heated above eutectic point) as the heat treatment holding time increases (15e60 min). Ring-shaped Al 3 Ni 2 around the Ni wires and in-matrix rosette-like Al 3 Ni ensue in the composites formed at under and above eutectic heat treatment respectively. Sub-eutectic heat treatment of the composite produced the better tensile strength (76.99 MPa) and toughness (230.56 KJm 3 ) as compared to the composite heat treated above the eutectic temperature (70.09 MPa and 90.06 KJm 3 ). The fracture morphologies agree with the tensile results. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Among the list of aluminide based (Ni-Al, Nb-Al, Fe-Al, and Ti- Al) materials, Ni-Al, Ti-Al, and Fe-Al alloys are the most utilized intermetallic compounds for technological applications owing to their low density, excellent stiffness, corrosion and oxidation resistance, and strength at elevated temperatures [1e3]. The solu- bility of Ni in Al promotes the formation of five different temperature-dependent intermetallic compounds such as Al 3 Ni, Al 3 Ni 2 , AlNi, Al 3 Ni 5 and AlNi 3 [4e7]. These Ni-aluminide interme- tallic compounds have been found to be suitable for several in- dustrial areas such as automotive, aerospace and power generation industries [4]. The intermetallic crystals of Al x Ni y have different properties as compared to the surrounding Al matrix owing to the chemical bonding between the atoms [5]. This phenomenon pro- vides a wide window for the improvement of mechanical properties by varying the type and morphology of the inherent Al x Ni y intermetallic compounds in Al-Ni alloys. Different techniques such as thermal annealing in vacuum [8], casting, powder metallurgy, sintering, mechanical alloying, com- bustion synthesis, hot pressing, hot rolling, and extrusion have been employed in the production of Al x Ni y structural materials [4,6]. Reaction synthesis (reactive infiltration) of Ni aluminide provides a convenient approach for the production of various Al x- Ni y intermetallic compounds. Choi et al. [9] investigated the gen- eration of intermetallic compound reinforced composites (with porous nickel and Al substrates) using the low-pressure infiltration method. It was reported that an increase in the temperature of the molten Al induced a corresponding increase in the amount of granular and needle-like Al 3 Ni in the developed composites. Wang et al. [10] investigated the formation dynamics of bulk b- Al 3 Ni phase in eutectic Al-5.69 wt%Ni alloy synthesized under altered pressures (1e2 GPa). It was shown that microstructural variation of large bulk b-Al 3 Ni and aAlþb-Al 3 Ni eutectic phases coexisted in the alloys subjected to high pressure while interfacial solidification velocity decreased under high pressure. Cui et al. [11] disclosed that * Corresponding author. E-mail address: m.paidar@srbiau.ac.ir (M. Paidar). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2018.11.408 0925-8388/© 2018 Elsevier B.V. All rights reserved. Journal of Alloys and Compounds 780 (2019) 829e845