Thoeretical Prediction Of Interfacial Reaction And Work Of Adhesion In SiC/Al Composites

In the preparation of composite materials using liquid state method,the wetting and adhesion properties between liquid matrix andreinforcement are the key factors for efficient combination. These factorsare important in determining the ease with which reinforcement can beadded or dispersed, the bonding strength of the interface as well as themechanical properties of the resultant composites. In addition, interfacialreactions are common at high temperature of the liquid state method. Theenergy released and the materials transported will have a great effect onthe wetting and adhesion properties. However, few research have beenconducted on thermodynamically investigating the variation of wetting oradhesion properties when reaction is involved.Focusing on the promising Al/SiC composites, the change rules of thework of adhesion under the condition of reaction were investigated.Combining interfacial reaction thermodynamics and work of adhesionmodels, a methodology was proposed to demonstrate how to calculate thework of adhesion in a reactive multicoponent alloy/ceramic system.Applying this methodology, the interfacial reaction and work of adhesion ofAl-X/SiC and Al-X/SiO₂/SiC systems and the influence of different alloyingelements were predicted. Experimental data were used to verify thereliability of the methodology.For Al-X/SiC system, the alloying elements Si, Cu, Ni could reduceequilibrium Si content, thus suppressing interfacial reaction, but thealloying elements Ti, La, Mn, Fe, Mg, Zn, when added in small amount,could increase equilibrium Si content and promote interfacial reaction.With respect to work of adhesion, La had obvious effect on promoting both initial and equilibrium work of adhesion while Zn could decreaseequilibrium work of adhesion, the other alloying elements showeddifferent effects for different states.For Al-X/SiO₂/SiC system, the addition of Mg led to the preferentialreaction between Mg and SiO₂, which produced MgAl₂O₄or MgOdepending on the Mg content, but other alloying elements had minimaleffect on equilibrium Si content, therefore control of kinetic factors wasrequired. For work of adhesion, Mn is outstanding in promoting work ofadhesion of both states while Si could reduce equilibrium work ofadhesion to a large extent. The effect of other elements depended on thespecific state.The results obtained could provide theoretical guidance for thepreparation of Al/SiC composites with different alloy additions.