In this work Small Punch Test (SPT) [1] was applied to study the mechanical behavior of ultrafine-grained Al-Al₂O₃metal matrix composites (MMCs) fabricated in situ via powder metallurgy[2] route (HITEMAL®). Such MMCs show attractive mechanical properties, enhanced creep performance and increased thermal stability at elevated temperatures, not normally associated with service of conventional Al alloys, even after prolonged high temperature exposure. MMCs fabricated from two powders of different particle size (d₅₀ = 8.9 and 1.2µm) were evaluated in this work.

SPT was performed at room temperature using specimens of 10 mm in diameter. The effects of thickness on load vs. displacement curves were also evaluated by specimens with thicknesses of 0.4, 0.5 and 0.6 mm. The displacements representative from top and bottom faces of the specimen showed differences along the test. The development of typical plastic stages [3] along the tests up to maximum often found for ductile materials is analyzed. The correspondence between load-displacement curve with stress – strain tensile curves for both composites is also analyzed. The characteristic load P_Y [4] defines the change between the first elastic bending regime and the plastic bending regime. The selection criteria to calculate P_Y of in terms of two methods are discussed. Using this SPT parameter the relationship with it corresponding yield stress is studied for each composite material. In particular the manufacture processing of 1.2 µm grain size was evaluated by SPT. A drastic change of mechanical behavior between the compacted powder previous and the hot forged material was detected.