Mechanical behavior of Be-Al alloys

Abstract

This study was conducted to identify the mechanical behavior of a wrought 62Be-38Al alloy and a cast 65Be-32Al-3Ni alloy. Tensile strength and elongation were measured at room and elevated temperatures. Fracture toughness was determined at room temperature. Fatigue resistance was characterized in terms of stress-life (S-N) and crack growth rate-stress intensity range (da/dN-ΔK) relations at room temperature. The resulting microstructures and crack paths of the aforementioned were also examined. The microstructure of the wrought and cast alloys consists of Be-phase particles dispersed within an Al-phase matrix. The Be-phase particles are aligned along the rolling direction in the wrought alloy, whereas they are coarser and round with no directionality in the cast alloy. Overall, the wrought alloy has better mechanical properties, including fatigue resistance, than the cast alloy. The conditional plane strain fracture toughnesses of the wrought alloy were determined to be 38. 8 and 22.4 MPa√m (35. 3 and 20.4 ksi√in) for the L-T and T-L orientations at room temperature, respectively. The crack path follows preferentially along the Al-phase and the Al/Be interfacial region for the wrought alloy at all temperatures and for the cast alloy at higher temperatures during tensile, fracture-toughness, and fatigue testing. However, while tensile testing at room temperature, the crack cuts through the Be- and Al-phases in the cast alloy.