IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) ISSN: 2278-1684 Volume 4, Issue 6 (Jan. - Feb. 2013), PP 16-21 www.iosrjournals.org www.iosrjournals.org 16 | Page Influence of Heat Treatment on Microstructure and Hardness of Nickel Aluminium Bronze (Cu-10al-5ni-5fe) Prabhash Jain 1 , Praveen Kumar Nigam 2 1 (Head, Department of Mechanical, BUIT, BU, Bhopal, India) 2# (Department of Mechanical, BUIT, Bhopal, India) Abstract : In this investigation two types of heat treatments, solutionizing and ageing were employed to nickel- aluminium bronze (NAB alloy) containing 10% Al, 5% Fe and 5% Ni as the alloying elements. Heat treatment was done to access their influence on the microstructural and hardness. Solutionizing temperature carried out at 850 o C and 900 o C for duration of 30 min, 60 min, 90 min and 120 min. similarly, ageing was carried out at 300 o C and 500 o C for the duration of 120 min and 180 min. The heat treated samples were subjected to water quenching in order to bring them to ambient temperature. Microstructural studies was also carried out of as cast alloy as well as after Solutionizing and Ageing.Hardness of the samples was measured in as cast and heat treated (solutionized and aged at different temperatures and durations) conditions. The hardness of the alloy increased after the solutionizing and ageing treatments compared to the as cast one. Also, the samples aged at 400 o C for 3 hrs attained the highest hardness. Optimization was done based on the best combination of hardness and microstructural homogeneity attained by the samples during the heat treatment. Keywords - NAB, Microstructure, Hardness, Solutionizing, Ageing I. INTRODUCTION Aluminium bronze is one of the versatile wear resisting engineering materials that work under a corrosive environment with high stress [1]. As we know that Aluminium bronze that is copper based alloy contains aluminium about 5 to 12 % or sometimes up to 14% by weight with some optional alloying elements like Fe, Ni, Mn and Si etc. [2][3]. Nickel–aluminium bronze (NAB) belongs to group of aluminium bronzes. It contains 9–12 wt. % aluminium with additions of iron and nickel up to 6 wt. % [4]. Nickel-aluminum bronze is a series of copper-based alloy with additions of aluminum, nickel and iron. Combined with high strength, it shows good resistance to corrosion and wear, which makes it one of the most versatile engineering materials. It is widely used as engineering parts, such as various worm-gears, gears, bearings, dies, valves and propellers [5]. The Chemical Composition of nickel aluminum bronze are 78% Cu min, 10.0% to 11.5% Al, 3.0% to 5.0% Fe, 3.5% Mn max, 3.0% to 5.5% Ni, 0.5% max other (total)[6] . The main microstructural phase of such copper alloys is the fcc Cu rich α phase. Cu-10Al binary alloys suffer from the formation of brittle eutectoid phases limiting their technical use. Alloying with Ni (about 5 wt%) retards this eutectoid formation and further alloying with Fe (3-5 wt%) leads to the formation of fine dispersed Fe 3 Al and NiAl type precipitates (so called k-phases) that usually do not tend to segregate at grain boundaries. In principle, such multiphase aluminum bronzes are heat treatable. Quenching from elevated temperature produces an extremely hard and brittle martensitic structure (β -phase) and subsequent tempering may be used to produce the desired combination of strength and ductility [7]. II. METHODOLOGY The methodology adopted to carry out the present study essentially involved alloy preparation by melting and casting technique, its heat treatment (solutionizing and ageing) over a range of temperatures and durations, optimization of heat treatment parameters (temperature and duration), sample preparation from the alloy in as cast and heat treated conditions, characterization of microstructural features and mechanical properties. A schematic representation of the adopted methodology is shown below (Fig 2.1):