Neutron diffraction study of elastoplastic behaviour of Al/SiC p metal matrix composite during tensile loading and unloading Sebastian WROŃSKI 1,a , Andrzej BACZMAŃSKI 1,b , Anita GAJ 1,c , Krzysztof WIERZBANOWSKI 1,d , Michael E. FITZPATRICK 2,e , Vincent KLOSEK 3,f , Alain LODINI 4,g and Marianna MARCISZKO 1,h 1 AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków, Poland 2 Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK 3 CEA, Laboratoire Léon Brillouin, 91191 Gif-sur-Yvette Cedex, France 4 LACM-DTI, Université de Reims Champagne Ardenne, UFR Science, Moulin de la Housse, 51100 Reims, France a wronski@ftj.agh.edu.pl, b baczman@ftj.agh.edu.pl, c gaj.anita@gmail.com, d wierzbanowski@fis.agh.edu.pl, e m.e.fitzpatrick@open.ac.uk, f vincent.klosek@cea.fr, g alain.lodini@univ-reims.fr, h mmarciszko@gmail.com Keywords: metal matrix composite, residual stress, X-ray diffraction, elasto-plastic deformation, self-consistent model, tensile load Abstract. The aim of the present work is to study effects occurring during elastoplastic deformation and unloading of Al/SiC p metal–matrix composite material. We have measured lattice strains for both phases independently using two separated diffraction peaks (the {111} reflections of Al and SiC) during in situ tensile testing. Lattice strains were measured in the direction parallel to the applied load. The results were compared with an elastoplastic model in order to find parameters determining the plastic deformation of the Al matrix (critical resolved shear stress and hardening parameter). We have found that during initial deformation relaxation of the thermal stresses occurs in both phases. Afterwards, the distribution of strains measured during the in situ test and unloading of the sample agree very well with self-consistent model predictions. Material The material used in this study was Al2124 alloy reinforced with 25% by weight of 3 µm SiC particles, produced by a powder metallurgy process. A plate of the composite was solution heat- treated at 505˚C for 2 h. One sample was quenched in cold water and naturally-aged, while the second sample was slowly cooled in air. In this way, two specimens were obtained: CWQ – cold water quenched sample with a hard matrix; and SQ – slowly cooled sample with a relatively soft matrix. The CWQ sample is harder owing to precipitation of intermetallic phases (mainly CuAl 2 ) during aging [1]. These precipitates can block movement of dislocations in the aluminium matrix and consequently increase the hardness of the Al/SiC p composite. For the slowly cooled sample larger precipitates do not make a significant contribution to strengthening [2]. The microstructure of the studied material is presented in Fig. 1. Experimental techniques The samples were studied on the G5.2 neutron spectrometer at the Laboratoire Léon Brillouin, Saclay, France. An incident neutron wavelength of 3.3688±0.0004Å was used to examine the {111} diffraction peaks for both Al and SiC phases. The reference d 0 parameter for stress free material was obtained using Al and SiC powders. The elastic lattice strain <ε el > {hkl} measured along the loading axis and corresponding to the applied external load is given by: Materials Science Forum Vol. 772 (2014) pp 117-121 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.772.117 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 149.156.110.250, AGH University of Science and Technology, Kraków, Poland-14/11/13,20:13:17)