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Mechanical Properties Refinement of Magnesium Alloy AZ91 via Cyclic Compression-Expansion Extrusion (CCEE) Method
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor)
Abstract
Cyclic Contraction Expansion Extrusion (CCEE) is a new Severe Plastic Deformation (SPD) method used to refine the microstructure and improve mechanical properties of Magnesium AZ91 alloy. In this study, different CCEE process zones are investigated via optical microscopy to understand this process better. The average grain size in the contraction zone decreased to 8.5 microns from an initial value of 106 microns. In the expansion zone, the average grain size was equal to 4.8 microns. Microhardness tests were conducted to study the improvements in mechanical properties. Microhardness of the sample increased from the initial value of 66 HV to 74.4 HV in the contraction zone and 88 HV in...
, Ph.D. Dissertation Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
The aim of this study was improvement of mechanical properties and grain refinem ent of aluminum 6061 alloy tubes by combining pre and post heat treatments with Tube Channel Pre ssing (TC P) as a new severe plastic deformation process. For this purpose , the effect of geometr i cal parameters of TCP on deformation behavior was studied at first. Then , the effect of pre and post heat treatments on mechanical properties improvement and micro structure was invest i gated. Finally, the effect of TCP process on mechanical properties improvement and grain refinement was considered. Results show that the mandrel design must follow die design in TCP. As an illustration ,...
Microstructural and mechanical characteristics of AA1050/mischmetal oxide in-situ hybrid surface nanocomposite by multi-pass friction stir processing
, Article Surface and Coatings Technology ; Volume 388 , 2020 ; Ebadi, M ; Alishavandi, S ; Kokabi, A. H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Surface hybrid in-situ aluminum matrix nanocomposite (AMNC) was fabricated by multi-pass friction stir processing (FSP) and a tool traversing speed of 100 mm/min and rotating speed of 1600 rpm with an objective to enhance mechanical properties. Mischmetal oxide (MMO) powder with an initial size of 50 nm, at a concentration of 8.5 vol% was used as the reinforcing particles. EDS particle analyses revealed in-situ solid-state chemical reactions between the Al matrix and the MMO particles. The reaction products, MM3Al and MM3Al11, were distributed uniformly in the discontinuously dynamic recrystallized nano and UFG microstructure. Increasing pass number improved the particle distribution and...