EFFECT OF REACTIVE HEAT TREATMENT ON PROPERTIES OF Al-Mg-B_4C COMPOSITES

摘要

Metal matrix composites consisting of boron carbide (B_4C) particles in an Al alloy matrix have been well studied due to their utility in various structural and nuclear (neutron absorbing) applications. In addition, prior work exists where such composites have been reactively heat treated to yield lightweight and hard ceramic-like materials consisting of Al-B-C ternary phases. The present work expands on this prior work and examines the quantnary Al-Mg-B-C system. The advantages of this system are reduced density due to the presence of Mg, and the ability to form the ultra-hard AlMgBu phase under the correct processing conditions. Composites were made by infiltrating preforms of B4C particulates with molten Al-Mg alloy. Key variables were Al:Mg ratio of the alloy and residence time at temperature (i.e., reaction time) after infiltration. The results demonstrate that composites with properties ranging from metal-like to ceramic-like can be produced in the experimental space studied, and that significant opportunities for additional optimization exist. In particular, longer reaction times led to increased formation of hard reaction products, and the use of an alloy of nominally 75A1 - 25Mg resulted in the greatest reaction rate (i.e., greatest formation of hard phases).