ORIGINAL RESEARCH ARTICLE Microstructure, Mechanical, and Tribological Relationship in Cu-12Al-Ni Alloy with Respect to the Variation of Ni Content Renu Prava Dalai, Sushree P. Mohapatra, Debasis Nayak, Dinesh K. Mishra, and Ajit Behera Submitted: 19 May 2023 / Revised: 29 June 2023 / Accepted: 14 July 2023 Powder metallurgy is an effective method to produce Cu-Al-based alloys for automotive and aerospace engineering components. The finer grain size, low cost, and low-temperature synthesis make this process more suitable than the other conventional production method such as melting and casting. The addition of Ni (austenite stabilizer) into the Cu increases the stability of Cu and refines the grain size. Again, the addition of Ni into the Cu-Al alloy increases the strength and hardness. In the present work, Cu-12Al alloys are developed by varying the wt.% of Ni content from 0 to 8 using powder metallurgy process through mechanical alloying method. Mechanical alloyed powder mixture is compacted by applying a load of 5 tons and sintered at 850 °C for 1 h under nitrogen atmosphere. It is found that a-Cu, c 2 -Cu 9 Al 4 , and NiAl phases are presented in the Cu-12Al-Ni alloy which influences the properties of the alloy. The theoretical, sintered, and relative density values are decreased with increasing the wt.% of Ni content. However, the Vickers hardness of the alloy is improved by increasing the wt.% of Ni content up to 4 wt.% and then reduced for 8 wt.% of Ni content due to the coarsening and network-type structure of the NiAl phase. A higher amount of wear loss or wear rate is observed for the Cu-12Al and Cu-12Al-2Ni alloy than the Cu- 12Al-4Ni and Cu-12Al-8Ni alloy. The presence of oxygen peaks in the EDS analysis revealed that an oxidative type of wear is occurred for the Cu-12Al alloy samples with varying the wt.% of Ni content. The electrochemical corrosion analysis revealed that the rate of corrosion is higher for Cu-12Al alloy without Ni. However, the rate of corrosion is reduced by increasing the wt.% of Ni content from 2 to 8. Keywords corrosion rate, Cu-12Al-Ni alloy, Cu 9 Al 4 , mechanical alloying, NiAl phase, wear rate 1. Introduction Mechanical alloying with powder metallurgy is the most appropriate method to develop the ternary and quaternary alloys. Finer grain size, high production rate, low processing temperature, energy saving, and cost-effectiveness are the main characteristics of the powder metallurgy process compared to the conventional high-temperature melting casting process. The unique advantage of the powder metallurgy process was to generate homogeneous microstructure and fine particles through mechanical alloying which significantly improved the physical, mechanical, and tribological properties of the ternary and quaternary alloys to a great extent (Ref 1-5). Cu-Al alloys show high hardness than pure Cu due to the solid solution strengthening (Ref 6). A further low density of Al reduced the weight of the Cu alloy. However, the addition of Ni to the Cu- Al alloys improved the hardness, strength, and toughness by forming the intermetallic compound NiAl (Ref 7-9). Further addition of Ni enhanced the chemical stability of the Cu-Al alloy (Ref 10). Cu-Al-Ni alloys are considered as a new combination of materials used for preparing the sliding bearings and self-lubricating sleeves due to their good mechanical properties and excellent wear resistance property (Ref. 11). Among the various Cu-Al alloys, Cu-12Al alloys are widely used in different industries with high strength, hardness, and high elastic properties (Ref. 12). The Cu-12Al binary phase diagram shows the alloy exhibits eutectoid microstructure (Ref 13). Zhenghua Deng et al. (Ref. 14) reported that 6 wt.% of Ni added Cu alloy with 12 wt.% Al content refined the a-Cu phase, reduced the bulk c 2 -Cu 9 Al 4 phase, and increased the amount of the intermetallic NiAl phase. However, they also mentioned that the below 4 wt.% of Ni content is unable to form the intermetallic phase NiAl. They also observed that with an increase in the wt.% of Ni content in the alloy, density of the developed alloys is reduced. The intergranular cracking, high anisotropy, and large grain size are the main reasons for the poor ductility of the Cu-Al-Ni alloys (Ref 15). Many researchers reported that the ductility can be enhanced by the addition of another element to form a quaternary alloy or by the use of grain refiners or by processing the alloy by powder metallurgy route or by rapid solidification method. Processing of the alloy by powder metallurgy route can improve the strain by up to 14.5% during deformation (Ref 16). Vajpai et al. (Ref 17) studied the mechanism of microstructure evaluation of a Cu-14Al-4Ni alloy through mechanical alloying, and they Renu Prava Dalai, Sushree P. Mohapatra, Debasis Nayak, and Dinesh K. Mishra, Department of Metallurgical and Materials Engineering, Veer Surendra Sai University of Technology, Burla 768018, India; and Ajit Behera, Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela, Odisha 769008, India. Contact e-mail: beheraajit@nitrkl.ac.in. JMEPEG ÓASM International https://doi.org/10.1007/s11665-023-08538-5 1059-9495/$19.00 Journal of Materials Engineering and Performance