EFFECT OF MICRO-ALLOYING ON THE STRUCTURE AND MECHANICAL PROPERTIES OF AL-4%CU ALLOY

AUTHOR: NNAKWO KINGSLEY CHIDI

DEPARTMENT: METALLURGICAL AND MATERIALS ENGINEERING

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

The effect of micro alloying on the structure and mechanical properties of aluminium-4% copper alloy was studied using standard techniques. The dopants were added in concentrations of 0.25%, 0.5%, 0.75%, and 1% by weight by mixing with stirrer and cast by gravity die casting. Subsequently the specimens were subjected to machining. The mechanical properties such as ultimate tensile strength, hardness and impact strength were determined for each specimen using universal testing machine (SRNO0723), Brinel hardness tester and universal impact testing machine (U1820) respectively. The microstructure of the samples was also studied using metallurgical microscope (L2003A) with image analysis software for measuring grain size and dendrite arm spacing and the photographs taken. The results showed that the ultimate tensile strength and hardness value of the alloy increased with increase in the concentration of magnesium and zinc. An increased ultimate tensile strength was also observed as the concentration of calcium increased. Manganese reduced all the mechanical properties in the order of its increasing concentration. The micro-structural analysis result showed that addition of magnesium reduced the grain size. Manganese retarded the precipitation of the strengthening phases in the alloy in the order of its increasing concentration. Results obtained showed a striking dependence of the mechanical properties on the atomic sub-structure of the dopants, such as atomic size and valence electrons concentration.

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