A Study On Compressive Deformation Behaviors Of In Situ Al₂O₃-TiCp/Al Composites At Elevated Temperatures

The in-situ Al₂O₃-TiC/Al (ZL109) composites were fabricated by melting and casting technique. The phases in the composites were identified by XRD. The distributions and morphologies and sizes of Al₂O₃ and TiC particles were observed and determined by SEM. The compressive tests at elevated temperatures were conducted on the CSS-44500 tensile machine with a heater attached. The compressive behaviors of the composites and pure industrially aluminum and ZL109 alloy were described. The microstructures fore and after hot compressive deformation were analyzed by TEM. The sensitivity indexes of strain rate ( m ) and apparent activation energies (Q) of the test material composites at different test conditions were calculated, and deformation mechanisms were discussed at elevated temperatures.The flow stresses of the test materials decreased with temperature increasing under the same strain rate. The flow stress fell down sharply at 723K. The flow stresses increased with increasing of strain rates under the same temperature.The TEM results showed that the dynamic recovery occurred in the compressive materials at 523K. The elongated grains and few dislocations in the grains and dislocation wall along grains were seen in the pure industrially aluminum. The dynamic recrystallizations occurred near the reinforced particles and dynamic recovery far from the particles for composites and ZL109 alloy..The sensitivity indexes of strain rate increased with temperature increasing ranged from 0.01s-1 to 1s-1. There existed different deformation mechanisms at different temperatures in the materials. The thermal activation energies of all test material composites were lower than the thermal activation energy of self-diffusion of grain boundary ranged the temperatures from 523K to 623K, which indicated that the deformation mechanism were characterized by sliding and climbing of dislocations in the grains. From 623K to 723K, however, the deformation mechanisms were different. The deformation of pure industrially aluminum were same as those from 523K to 623K. And the deformation mechanism of other three material composites were characteristic of creeping of grain boundaries, for thermal activation energy of pure industrially aluminum were lower than others when the temperature was from 623K to 723K.