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The Process of Ultra-fine Multi-scale5083Al by ARB

Author: LiShuLei
Tutor: LinYaoJun
School: Yanshan University
Course: Materials Science
Keywords: Hardness Annealing ARB Single layer subgrain Geometricrecrystallization
CLC: TG339
Type: Master's thesis
Year: 2013
Downloads: 1
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Abstract


The ultra-fine grain which was made by traditional process has high strength, but thetoughness is poor. This experiment refine the5083aluminum alloy material throughmechanical heat treatment method, and on this basis, we use the ARB technology todecrease the grain boundary spacing to sub-grain size. The low temperature annealinginduced ultra-fine grain boundary migration to obtain good performance of aluminumalloy material. By scanning electron microscope (SEM), transmission electron microscope(TEM), optical microscope for aluminum alloy microstructure was characterized, and theformation and evolution of organization was discussed. Mechanical properties of ultra-fine5083Al were tested (including microhardness, tensile properties), fractograph wasobserved and the mechanical performance was studied deeply.The conventional rolling aluminum alloy which was annealed at300℃for0.5h wascharacterized by optical microscope and grain size is about10um. Using TEM toanalysis the sample which was deformed for2times at200℃, elongated grains withhigh density of dislocations, and isometric grains existed at the same time. When theARB process reached5times, a single sub-grain structure, and a region of geometryrecrystallization with high density of dislocation were produced. The number of ARBreaches6, the single crystal organization is thinner, even reached0.1um, and more areasappeared geometric recrystallization phenomenon.To anneal the specimen at200℃.With the extended of annealing time, the numberof equiaxial grains increased, but there are still quite a number of maintaining the originalappearance, the equiaxial crystal size is less than0.3um. When the temperature reached225℃, more areas appeared equiaxial grains, and the size of grains grown, the width ofsingle sub-grain changed, grain size is less than0.5um. As temperatures rise further, asharp drop in hardness,250℃when hardness decreased to100hv,300℃when thehardness is80HV.In ARB processing, a layer of nanocrystalline was formed by friction.Due to theintensity pinning effect of the alumina makes these nanocrystals in the process at low temperature annealing retained the original appearance did not grow up.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal pressure processing > Rolling > Non-ferrous metal rolling
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