Microstructure characterization of Al matrix composite reinforced with Ti-6Al-4V meshes after compression by scanning electron microscope and transmission electron microscope

摘要

Compressive properties of Al matrix composite reinforced with Ti-6Al-4V meshes (TC4_m/5A06 Al composite) under the strain rates of 10~(-3) S~(-1) and 1 S~(-1) at different temperature were measured and microstructure of composites after compression was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compressive strength decreased with the test temperature increased and the strain-rate sensitivity (R) of composite increased with the increasing temperature. SEM observations showed that grains of Al matrix were elongated severely along 45° direction (angle between axis direction and fracture surface) and TC4 fibres were sheared into several parts in composite compressed under the strain rate of 10~(-3) S~(-1) at 25℃ and 250℃. Besides, amounts of cracks were produced at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al_6 phases. With the compressive temperature increasing to 400℃, there was no damage at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al_6 phases, while equiaxed recrystal grains with sizes about 10 μm at the original grain boundaries of Al matrix were observed. However, interface separation of TC4 fibres and Al matrix occurred in composite compressed under the strain rate of 1 S~(-1) at 250℃ and 400℃. With the compressive temperature increasing from 25℃ to 100℃ under the strain rate of 10~(-3) S~(-1), TEM microstructure in Al matrix exhibited high density dislocations and slipping bands (25℃), polygonized dislocations and dynamic recovery (100℃), equiaxed recrystals with sizes below 500 μm (250℃) and growth of equiaxed recrystals (400℃), respectively.