Synthesis of aluminum alloy 7075-graphite composites by milling processes and hot extrusion

Aluminum alloy 7075 (Al7075) and composites of Al7075 with different concentrations of graphite particles (Al7075-G) were synthesized from elemental powders by a milling process. Milled products were consolidated by pressureless-sintering followed by hot extrusion. The mechanical properties of the sintered specimens were evaluated by tension tests and hardness measurements. Variation of Zn and graphite contents and their effect on mechanical properties was characterized. The results obtained show that the yield strength (σy), the maximum strength (σmax) and the Vickers microhardness (μHV) were enhanced as a function of graphite particles content and milling time, but the elongation was reduced significantly in some cases.

Research highlights▶ Aluminum 7075 alloy–graphite composites were synthesized by mechanical alloying. ▶ Graphite particles were used as the reinforcement material. ▶ The density of the composites was decreased by decreasing the Zn content. ▶ Mechanical properties are enhanced by increasing milling time and graphite content. ▶ Several strengthening mechanisms are proposed.