Study On The Microstructure And Properties Of Al-Ti-C Alloy Processed By Conform-ECAP

Equal Channel Angular Pressing(ECAP)is a severe plastic deformation process that can make large-size ultrafine-grained materials.In this paper,ECAP technology and continuous extrusion(Conform)are combined to press the Al-5Ti-0.2C in a continuous manner.The microstructure of the deformed material was observed by optical microscope,scanning electron microscope(SEM)and transmission electron microscope(TEM),and the mechanical properties of the deformed material were measured by Vickers hardness tester and friction and wear tester.The mechanical properties,microstructure evolution and grain refinement mechanism of Conform-ECAP extruded with different passes were investigated.The evolution of the second phase particles of Al3Ti and TiC in the alloy was also studied.The experimental results show that Conform-ECAP can effectively improve the mechanical properties of Al-5Ti-0.2C alloy.The hardness of Al-5Ti-0.2C alloy increased significantly after deformation for one pass,and then the hardness increased slowly with the increase of extrusion pass.The wear resistance of Al-5Ti-0.2C alloy also increased after extrusion.After 4 passes of Conform-ECAP extrusion,the Al-5Ti-0.2C alloy matrix grains were reduced from 35μm to 0.8-1.5μm from the original as-cast.The deformation induction is the most important grains refinement mechanism of Conform-ECAP.In the initial stage of Conform-ECAP extrusion,Al-5Ti-0.2C alloy continuously produced dislocations in the structure and the fraction of LAGBs(Low Angle Grain Boundaries)in Al-5Ti-0.2C alloy was rapidly increased at the beginning of ECAP process.With the increase of ECAP pass,LAGBs(Low Angle Grain Boundaries)gradually transformed into HAGBs(High Angle Grain Boundaries),which indicated that new grains appeared and the average grain size was decreased.In the process of Conform-ECAP,a large number of dislocations were generated in Al3Ti with the rapid increase of deformation.With the continuous extrusion,the crack grew,causing the Al3Ti to be broken and refined.During the Conform-ECAP process,the distribution of TiC particles in the Al matrix becomes slightly uniform and the size morphology does not change obviously.However,it played a positive role in the continuous refinement of Al matrix and the breakage of Al3Ti particles.