SAP-like ultrafine-grained Al composites dispersion strengthened with nanometric AlN

This paper reports the development of novel Sinter-Aluminum-Pulver (SAP)-like Al-AIN nanocomposites via replacing the native Al2O3 thin films on fine Al powder with a large volume fraction of in situ formed nanometric AlN dispersoids. Fine gas-atomized Al powder (d(50) = 1.3 mu m) compacts were first partially nitrided at 590 degrees C in flowing nitrogen, controlled by a small addition of Sn (03-0.4 wt%), and subsequently consolidated by hot direct extrusion. The resulting Al-AIN composites consisted of submicrometric Al grains reinforced with nanometric AlN dispersoids together with some nanometric Al2O3 dispersoids. An Al-13 vol% AlN nanocomposite fabricated this way achieved exceptional ultimate tensile strength of 227 MPa, yield strength of 195 MPa and Young's modulus of 66 GPa at 300 degrees C, superior to typical SAP materials and coarse grained Al-AIN composites. In addition, the Al-13 vol% AlN nanocomposite exhibited good thermal stability up to 500 degrees C. The strengthening mechanism is discussed. (C) 2013 Elsevier BM. All rights reserved.