Influence of sintering on bending strength of underwater shock consolidated Al–SiC p composites H. Eskandari 1 , M. Emamy* 1 , H. M. Ghasemi 1 , K. Hokamoto 2 , J. S. Lee 2 and M. Mahta 1 Aluminium matrix composites containing 10, 20 and 30 vol.-%SiC particles were manufactured with underwater shock consolidation method. Sintering of the compact specimens was carried out at 400uC for 70 min. Density, hardness and bending strength of the specimens were measured before and after sintering treatment. SEM fractography examination was used for analysis of fracture surfaces of the consolidated specimens. The sintered specimens with 10 vol.-%SiC p showed enhancement in the bending strength and deflection. After sintering, the fracture surface of 10 vol.-%SiC p composite showed cleaved SiC particles, indicating appreciable improvement in bonding strength between ceramic reinforcement particle and Al matrix. Keywords: Al–SiCp composite, Underwater explosive compaction, Sintering, Bending strength Introduction Aluminium metal matrix composites (MMCs) have emerged as an important class of engineered materials with attributes such as high specific stiffness, strength and increased wear resistance over unreinforced alloys. Particulate reinforced aluminium matrix composites are most promising and economically viable. 1–3 Shock con- solidation such as underwater explosive compaction is a process which shows characteristics that differentiate it from the traditional powder metallurgy. These character- istics are: partial or total elimination of sintering ope- ration, the ability to compact alloys or powder mixtures which in conventional techniques would undergo chemical reaction during sintering, and the treatment of amorphous powders without degradation of original microstructure. 4 Underwater shock consolidation is a one stage densifica- tion process, which involves a very rapid and intense deposition of shock energy on particle surfaces. Among many reports 5–16 published on shock consolidation of powders, limited works 14–16 have been reported on under- water explosive compaction. Using the water apparatus can help to obtain uniform pressure distribution. The shock pulse can be regulated by the manipulation of the height of the water column. 13,16 Also, this process has the advant- age of obtaining a uniform microstructure in MMC. Two variations of underwater shock consolidation are widely employed: (i) converging assembly 17–19 (ii) straight cylindrical assembly. 16,20 The former technique is especially employed for compacting high strength metal powder. Shock synthesis of the aluminium and aluminium alloy matrix system (by axis symmetrical and underwater methods), the effects of consolidation parameters and microstructural variations with respect to the processing conditions have been investigated by some researchers. 21–28 It is well established that subsequent mechanical working or heat treatment is required to improve the mechanical proper- ties of the composites. The present investigation is an attempt to manufac- ture Al matrix composite reinforced with 10, 20 and 30 vol.-%SiC particles in one-dimensional underwater shock consolidation technique. The effect of sintering on mechanical properties has also been studied. Experimental procedure The base materials in the present work were spherical atomised pure aluminium powders with 45 mm mean size and SiC powders (.99% purity) with 15 mm mean size. The set-up for underwater explosive compaction is shown in Fig. 1. Powders were mixed in a conventional ball mill machine at y120 rev min 21 for 90 min under dry condition and then were mechanically packed into a plain carbon steel container with 30 mm inner diameter and 22 . 5 mm wall thickness. The powders were pressed using uniaxial press machine to a certain theoretical density at 0 . 6 and the pressure ranged between about 20 and 30 MPa. The ball mill container was an alumina based ceramic without any balls and just mixing was made in all experiments. The shock waves were generated using a planar impact system by the use of an explosive lens, which was made of a combination of two explosives, namely SEP and HABW. 1 Department of Metallurgy and Materials Engineering, University of Tehran, PO Box 11365–4563, Tehran, Iran 2 Shock Wave and Condensed Matter Research Center, Kumamoto University, Kurokami, Kumamoto 860–8555, Japan *Corresponding author email emamy@ut.ac.ir ß 2006 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 1 August 2005; accepted 27 August 2005 DOI 10.1179/026708306X81496 Materials Science and Technology 2006 VOL 22 NO 3 349