Study of particle–matrix interaction in Al/AlB2 composite via nanoindentation

Aluminum diboride (AlB2) particles enhance wear resistance of functionally-graded aluminum-AlB2 composites. A critical factor governing the wear resistance of these composites is the mechanical interaction between the diboride particles and the aluminum matrix. To study this interaction nanoindentation experiments were performed on 3–10 µm size AlB2 particles embedded in the aluminum matrix of an as-received Al–5 wt.%B alloy and a centrifugally cast one. Under large nanoindentation loads (2–8 mN) diboride particles could be pushed into the matrix. The results show that on a per unit area basis, smaller particles are more difficult to push-in than larger particles. Strain gradient plasticity (SGP) theory was used to explain the size dependence of the push-in force.