Trans. Nonferrous Met. Soc. China 23(2013) 53−58 Role of particle stimulated nucleation in recrystallization of hot extruded Al 6061/SiC p composites C. S. RAMESH 1,2 , R. KESHAVAMURTHY 3 , Praveennath G. KOPPAD 1 , K. T. KASHYAP 1 1. Department of Mechanical Engineering, PES Institute of Technology, Bangalore 560085, India; 2. Visiting Professor, School of Design, Engineering and Computing, Bournemouth University, United Kingdom; 3. Central Manufacturing Technology Institute, Tumkur Road, Bangalore 560022, India Received 12 March 2012; accepted 27 August 2012 Abstract: Studies on texture and microstructure evolution in hot extruded Al 6061 aluminium alloy reinforced with uncoated and nickel coated SiC p were carried out by electron backscattered diffraction technique. Textures of both the alloy and its composite with nickel coated SiC p do exhibit strong β fiber with its axis parallel to the direction of extrusion. In addition to the dominant cube texture (001)〈100〉, fully recrystallized grains with partially equiaxed structure have been observed in the alloy reinforced with uncoated SiC p . The recrystallization texture of this composite can be attributed to the particle stimulated nucleation (PSN) due to the presence of SiC p with size less than 5 μm. Under these conditions, the low value of Zener–Hollomon, Z (~ 10 12 s −1 ) confirms that PSN is one of the dominant mechanisms for recrystallization and is governed by formation of deformation zone rather than stored energy. Key words: metal matrix composites; 6061/SiC p composite; extrusion; particle stimulated nucleation; recrystallization; stored energy 1 Introduction Aluminium alloys of 6xxx series have been the material of choice for both aerospace and automotive applications because of their attractive properties. These aluminium alloys reinforced with hard and non-deformable ceramic particles such as SiC are of significant importance as they offer better mechanical and tribological properties [1,2]. SiC reinforced aluminium alloy composites can be readily shaped by secondary metal working processes, such as rolling and extrusion. These processes lead to the evolution of new microstructure and texture in aluminium alloys and their composites, which have been reported by few researchers [3,4]. However, the reports on texture evolution in hot extruded aluminium alloy based composites are very limited although the rolling textures of aluminium based composites have been studied in detail. The typical rolling textures of aluminium alloys and its composites are generalized as α and β fibers. The α fiber consists of goss (110)〈001〉 and brass (110)〈112〉 texture components, while the β fiber ranges from brass (110)〈112〉 through the S (123)〈634〉 and ends at Cu (112)〈111〉. The deformation and recrystallization behaviour of hot deformed aluminium alloys and composites is still a matter of intense research. POUDENS and BACROIX [3,5] have reported the deformation textures in Al−SiC composites of two fibers 〈111〉 and 〈100〉. They have observed increase in the intensity of 〈111〉 fiber during annealing of particle-free material. In the composites, the intensity of 〈111〉 fiber was sharper than the pure alloy when the matrix was reinforced with less than 10% SiC whereas for greater than 10% SiC, a decrease in intensity of 〈111〉 fiber was observed. It has been reported that SiC particles favour the particle stimulated nucleation (PSN) by nucleation of new grains in the deformation zones but to a small extent at low extrusion temperatures [6,7]. The recrystallized microstructure depends on the formation of the nuclei and growth in the deformed matrix, but the evolution of recrystallization texture is still a matter of controversy with two competing mechanisms, namely oriented nucleation and oriented growth, trying to describe the origin of recrystallization textures. The working temperature and the strain rate are related by Zener−Hollomon factor (Z). The factor Z is closely related to the microstructure and texture of the particle containing alloy as it is important to represent the effect of PSN as a function of working temperature. KRETZ et al [8] have studied the effect of nickel Corresponding author: C. S. RAMESH; Tel: +918026721983; Fax: +918026720886; E-mail: csr_gce@yahoo.co.in DOI: 10.1016/S1003-6326(13)62428-0