Mechanical behavior of A356 matrix nanocomposites fabricated using two step mixing via stir casting technique
In this work an investigation of compressive strength and forgeability behavior have been made to explore the effect of SiC nano particles on A356 alloy matrix for the development of A356/SiC nanocomposites using two step mixing through stir casting technique. A356 alloy ingot was selected as a matrix and AFP+SiCn (99.9% pure aluminium fine powder+nano size SiC mechanically forged by using ball mill at 100 rpm for duration of 10 hours) as a reinforcement. Argon gas was used to protect from oxidation during ball milling process. SiC nano particles were varied from 1% to 5% in a step of 1% by weight. In stir casting technique, stirring process was performed at 500±50 rpm for mixing AFP+SiCn in the melt matrix for total stirring period of 10 minutes in two steps. Composites were poured at 680±20° C into the permanent mould. Compressive strength and forgeability tests of fabricated nanocomposites were evaluated by using hydraulic pellet press machine. To analyze the fractured mechanism SEM microstructure was examined. The presence of SiC nano particles were confirmed by EDX spectrum. It was revealed from the results that compressive strength increases with increment of SiC nano particles and found as 603 MPa at 5% SiC nano particles. Whereas forgeability of the nanocomposites were decreased with the increment of SiC nano particles. SEM micrographs showed the ductile fractured mechanism was dominant over the brittle fracture. The main constituents present in the nanocomposites were verified by EDX spectrum.
Effect of matrix strength on the mechanical properties of Al–Zn–Mg/SiCP composites
The mechanical properties of Al-Zn-Mg alloy reinforced with SiCP composites prepared by solidification route were studied by altering the matrix strength with different heat treatments. With respect to the control alloy, the composites have shown similar ageing behaviour in terms of microhardness data at 135 degrees C. It was shown that 
although composites exhibited enhanced modulus values, the 
strengthening was found to be dependent on the damage that is occurring during straining. Thus the initial matrix strength plays an important role in determining the strengthening. Consequently, compression data had shown a different trend compared to tension. (C) 2000 Elsevier 
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Macroscopic shear localization and fracture of notched and unnotched Al–Zn–Mg–Cu bars
AbstractTensile tests of notched and unnotched Al–6Zn–2·3Mg–1·7Cu alloy bars have been carried out. The underaged and peak-aged unnotched specimens exhibit macroscopic shear localization during testing, followed by shear failure, whereas the overaged unnotched specimens exhibit the conventional ‘cup–cone’ mode of failure. The introduction of a notch changes the deformation pattern and the fracture mode of the specimens. Deformation is constrained within the notched region, and the triaxial tensile stress developed at the notch results in grain boundary splitting, which complicates the deformation pattern and failure mode. The fracture behaviour of these specimens is explained by an adaptation of crystal slip theory.MST/197