Investigation On Microstructure And Mechanical Properties Of Al-Fe Alloy Processed By Equal-channel Angular Pressing

Equal-channel angular pressing(ECAP)is one of the methods to produce ultrafine-grained and nanostructured materials via severely plastic deformation.It has been developed rapidly as a severely plastic deformation process due to its several advantages:sample size remains unchanged,the effect of grain refinement is significant,easy operation and so on.In this experiment,the effects of different ECAP extrusion passes on the microstructure and mechanical properties of the Al-1.5 Fe alloy and the A1-3 Fe alloy were studied by using the optical microscope,scanning electron microscope,X-ray diffraction,transmission electron microscope,tensile,hardness,electrical conductivity test.Al-1.5 Fe alloy was subjected to different annealing temperatures in order to investigate its thermal stability.The following main conclusions were obtained:(1)After ECAP pressing through different passes,grain size of the A1-Fe alloy was significantly refined,and the best grain refinement effect were obtained after 4 ECAP passes.In the A1-1.5 Fe alloy,the average grain size reached about 0.9 ?m.The grain was refined to about 0.7 ?m for the Al-3Fe alloy.With the increase of the ECAP passes,the content of the high-angle grain boundaries gradually increased.(2)Al3Fe phase in the Al-Fe alloy was fragmented after different ECAP passes.With the increase of ECAP passes,the level of Al3Fe phase fragmentation increased.The most obvious fragmentation was achieved after 4 ECAP passes.(3)The yield strength and ultimate tensile strength of the Al-Fe alloy increased significantly,whereas the plasticity decreased gradually with the increase of ECAP passes.Fracture mode of the Al-Fe alloy changed from distinct necking in pre-ECAP state to shear fracture mode.Electrical conductivity of the Al-Fe alloy decreased significantly after 1 ECAP pass,and then it gradually increased to the highest after 4 ECAP passes.(4)The Al-1.5 Fe alloy with different ECAP passes was annealed at different temperatures for 1 h.The banded structure disappeared gradually and recrystallization grain can be observed at 250?.The grains grew up quickly in the microstructure when the temperature increase to 350?.(5)The average grain size decreased with the increased ECAP passes in the alloy for the same annealing temperature,and the content of high-angle boundaries increased in the microstructure with the increase of annealing temperatures.The morphology and size of the Fe-rich phase did not change in the Al-1.5 Fe alloy after annealing at different temperature.The presence of the submicro-sized Al3Fe phase at sub-grain boundary and grain boundary can increase the recrystallization temperature of the Al-1.5 Fe alloy.(6)The ultimate tensile strength and hardness of the Al-1.5 Fe alloy decreased continuously,while the plasticity and electrical conductivity increased steadily with the increase of annealing temperatures.The fracture mode is changed from shear fracture mode to distinct necking fracture at annealing temperature of 300?.