Tensile fracture behaviors of thixocast, artificially aged thixocast （thixocast＋T6） and as-extruded AA7075 alloys were investigated. The microstructural and fractographic observations were carried out using optical...Tensile fracture behaviors of thixocast, artificially aged thixocast （thixocast＋T6） and as-extruded AA7075 alloys were investigated. The microstructural and fractographic observations were carried out using optical microscope （OM） and scanning electron microscope （SEM）. Experimental studies showed that as-extruded and thixocast＋T6 specimens exhibited considerably more excellent mechanical properties than as-thixocast AA7075 specimen. T6 artificial heat treatment with prolonged solution treatment significantly improved the tensile properties of the thixocast AA7075 alloy. The tensile properties of as-extruded and thixocast＋T6 specimens were close to each other. In as-thixocast specimen having remarkable micro-cracks, fracture was intergranular brittle type. The ductile fracture surfaces were observed in as-extruded and thixocast＋T6 specimens. In as-thixocast specimens, decohesion started between the eutectic-matrix interfaces and propagated through grains. Micro-void coalescence was the dominant form of fracture in thixocast＋T6 heat treated specimens. The micro-voids nucleation was initiated at the interface between the matrix and multinary eutectic structure.展开更多
基金the financial supports of the State Planning Organization of Turkey (DPT Project Number: 2003K120470-27)Gazi University Scientific Research Fund (GUBAP Project Number: 07/2013-01)
文摘Tensile fracture behaviors of thixocast, artificially aged thixocast （thixocast＋T6） and as-extruded AA7075 alloys were investigated. The microstructural and fractographic observations were carried out using optical microscope （OM） and scanning electron microscope （SEM）. Experimental studies showed that as-extruded and thixocast＋T6 specimens exhibited considerably more excellent mechanical properties than as-thixocast AA7075 specimen. T6 artificial heat treatment with prolonged solution treatment significantly improved the tensile properties of the thixocast AA7075 alloy. The tensile properties of as-extruded and thixocast＋T6 specimens were close to each other. In as-thixocast specimen having remarkable micro-cracks, fracture was intergranular brittle type. The ductile fracture surfaces were observed in as-extruded and thixocast＋T6 specimens. In as-thixocast specimens, decohesion started between the eutectic-matrix interfaces and propagated through grains. Micro-void coalescence was the dominant form of fracture in thixocast＋T6 heat treated specimens. The micro-voids nucleation was initiated at the interface between the matrix and multinary eutectic structure.
