Dissertation > Excellent graduate degree dissertation topics show

Supplemented by large deformation heat treatment asynchronous Roll Ultrafine twinned copper and its formation mechanism

Author: MiHui
Tutor: ShiQingNan
School: Kunming University of Science and Technology
Course: Material Forming and Control
Keywords: severe deformation asymmetrical accumulative rolling bonding the Ultra-Fine twin copper grain refinement stucture evolution mechanics property
CLC: TG166.2
Type: Master's thesis
Year: 2011
Downloads: 44
Quote: 0
Read: Download Dissertation

Abstract

The Ultra-Fine twin copper with fine special structure performs excellent properties,such as high strength,electrical conductivity and heat conductivityand so on.Therefore,the preparation and properties of the Ultra-Fine twin copper of research is a hot spot in metal materials field.Superstrength and high-cinductivity of the Ultra-Fine twin copper open a new research field for the reinforcement technique of material and the further research of material with strength and high conductivity, but also can be important raw material which is used in industrid department reference to the Machine,Ship building,Aviation,Chemical industry, Electrical instrumentation and so on. What’s more,the copper with superstrength and high-conductivity can also take great effect in the field of Magnet technology with superconductivity,Power transmission system,Micro-electromechanical system and related fields.The Ultra-Fine twin copper was obtained by AARB and treated by recrystallization annealing. On this basis,the structure and properties of the Ultra-Fine twin copper researched,and the result were as follows:1. The Copper with big grains was processed by AARB and the equivalent strain (ε) was equal to 4.8, the Ultra-Fine twin copper obtained is composed of lots of sub-structure. Then these Ultra-Fine twin coppers was heat-treated at 190℃for 25min and the Ultra-Fine twin copper with the grain sizes of 200-500nm has been prepared.2.The effect of the shearing stress during AARB was discussed:In order to produce homogeneous shearring strain which twinning is needed,the twinning dislocation of forming fault must lie in every plane and move orderly in F.C.C,or make sure dislocation cross every plane in parallel family of planes regularly.3. The mechanism of annealing twin copper during recrystallization was discussed:he nucleation of Shockley partial loops on consecutive{11I) planes by growth accidents on propagating{111) steps which are associated with a migrating grain boundary. The higher the velocity of the boundary, the higher the probability of growth accidents. Lateral growth of faults occurs due to a repulsive interaction between Shockley partials constituting the twin boundary.4.The effect of temperature on annealing twin was discussed:During recrystallization,growth-in-duced stacking faults are eliminated more frequently at higher temperature. As a result, for a given driving force for grain boundary migration, i.e. grain growth,lower twin densities may be produced at higher temperatures.5.The effect of shearing stress during AARB on annealing twin formed was discussed:The shearing texture{001}<110> rotated 54.7°and transform into twin texture {111}<211> during recrystallization.Crystal lattice motion by the action of shearing stress,and make perfect dislocation extend immobile Frank partial dislocation and twinning dislocation(i.e.Shockly partial dislocation).Then,the probability of annealing twin formation was greatly increase by growth of recrystallized grains.6. The property of Ultra-Fine twin copper was tested:The strength and the hardness rise at first,then decrease approximately with the longer annealing time,and the elongation rate and the electrical conductivity all go up with the longer annealing time,only rising slowly in later annealing process.The electrical conductivity of the Ultra-Fine twin copper which obtained at at 190℃for 25 minutes is the same to that of annealing copper of No.1

Related Dissertations

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Heat treatment > The heat treatment of non-ferrous metals and their alloys > The heat treatment of copper and its alloys
© 2012 www.DissertationTopic.Net Mobile