4866

4570

كارشناسي ارشد

شناسايي و انتخاب مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1388

نه،105ص.:مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمود مراتيان، محمدرضا طرقي نژاد

30/9/88

فخرالدين اشرفي زاده،حسين ادريس

مهندسي مواد

ID4570

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Evaluation of Mechanical Properties and Microstructure of Ultra Fine Grained 8090 Al Li Alloy by ECAP Process Mohammad Hossein Tahmasebi drmht@ma iut ac ir Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors M Meratian meratian@cc iut ac ir M R Toroghinejad toroghi@cc iut ac ir Abstract During last decades many attempts has been done for the development of severplastic deformation SPD process for producing ultra fine grained metals In thesetechniques severe plastic strains can be applied to solid bulk materials without anysignificant changes in the specimen s overall dimensions Among different SDP techniques ECAP has attracted most attention because it is effective in the production of UFGstructures In this research after 2 passes ECAP process and annealing at 520 oC for 2 hr ECAP process up to 10 passes was carried out on as cast 8090 Al Li alloy specimens withdifferent route A and Bc in the ECAP die with 120o at 250 oC Then for investigatingthe effect of precipitation hardening after the ECAP process 2 4 6 and 8 passes ECAPedsamples was precipitate hardened Microstructures of different samples were studied withEBSD equipment Tensile and hardness test were performed for evaluating the mechanicalproperties of ECAP samples before and after precipitation hardening In order to clarify thefailure mode fracture surfaces after tensile test were observed by Scanning ElectronMicroscopy SEM Moreover X ray diffraction system equipped by goniometer wasutilized to investigate the variation of texture of the samples The results showed that significant grain refinement was obtained by ECAP processand the grain size decreased from 30 micron in annealed sample to below 1 micron ultra fine range after 6 passes ECAP with route A It is observed that at first stages ofECAP process the hardness and tensile strength were increased and decreased bysubsequent passes Precipitate hardening of samples after ECAP processing results insignificant increase in hardness and tensile strength but elongation of the sample stronglyincreased as after 2 passes ECAP and precipitate hardening the hardness of the samplewas almost two times higher than the annealed sample Different routes and precipitatehardening result in different texture in samples The important point was brass texture 110 112 that was obtained after precipitate hardening Keywords ECAP 8090 Al Li tensile strength elongation texture ultra fine grainstructure

محمود مراتيان، محمدرضا طرقي نژاد

فخرالدين اشرفي زاده،حسين ادريس