The .7050a1/gr Composite Aging Hardening Behavior And Internal Friction Studies

By means of optical microscope, scanning electron microscope, transmission electron microscope, universal electronic tensile machine and multifunctional low frequency internal friction, the influences of 4vol%Gr on microstructure, mechanical properties and internal friction of 7050 alloy have been studied. And the influences of heat treatment on microstructure, mechanical properties and internal friction of 7050Al/4vol%Gr Metal Matrix Composites have been studied. The analysis and explanation in internal friction of 7050Al/4vol%Gr Metal Matrix Composites were also given. The results show that:1. In extruded condition, adding 4vol%Gr in the 7050 alloy, its tensile strength have decreased about 16%, and elongation have reduced 37.5%.2. The change trend of heat treatment to strengthen 7050Al/4vol%Gr Metal Matrix Composites is basically same. That is, it has better synthesis mechanical properties in the T6 single aged treatment more than the T76 and T77 multi aged treatment.3. Aging at 120℃, the mutative trend of 7050Al/4vol%Gr Metal Matrix Composites on tensile strength and elongation have agreed with 7050 alloy. But the peak strength of 7050Al/4vol%Gr Metal Matrix Composites decreased, and the peak aging time advanced 4 hours.4. Adding Gr particles don't obvious change to the aging precipitates of 7050 alloy. The precipitates has not been changed, mostly for theη' phase andη' phase.5. The internal friction peak of 7050Al/4vol%Gr Metal Matrix Composites increase following the temperature between 100℃and 250℃. The internal friction peak of different heat treatments 7050Al/4vol%Gr Metal Matrix Composites also increase following the temperature, and have a friction platform about 200℃. But the friction values of 7050Al/4vol%Gr Metal Matrix Composites are basically the same in T6, T76 and T77 three heat conditions.6. In addition to the intrinsic damping of 7050Al/4vol%Gr Metal Matrix Composites, the internal friction are mainly dislocation damping which are caused by the interaction of dislocations and second-phase particles in the low temperature; in the high temperature, the internal friction are mainly caused by the slippage whith the phase interface, grain boundaries, the interface of Gr and the matrix bring.