Complex study of multilayer al99 99 almg3 laminates prepared by accumulative roll bonding
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Complex study of multilayer Al99.99/AlMg3 laminates prepared by accumulative roll bonding . Miroslav Cieslar. Charles University in Prague, Faculty of Mathematics and Physics, Department of Physics of Materials, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic. Outline. Introduction

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Complex study of multilayer al99 99 almg3 laminates prepared by accumulative roll bonding

Complex study of multilayer Al99.99/AlMg3 laminates prepared by accumulative roll bonding

Miroslav Cieslar

Charles University in Prague, Faculty of Mathematics and Physics, Department of Physics of Materials, KeKarlovu 5, CZ-121 16 Prague 2, Czech Republic


Outline

Outline by accumulative roll bonding

Introduction

Material

ARB processing

Experimental methods

Microstructure

Mechanical properties

Electrical resistivity

Microstructure evolution

In-situ observations

Summary


Introduction
Introduction by accumulative roll bonding

  • Ultrafine - grained materials (UFG)

  • Most common methods: ECAP (Equal Channel Angular Extrusion or Pressing ), HPT (High Pressure Torsion )

  • Since 1998 – ARB (accumulative roll-bonding

Schematic diagrams of (a) ECAP (b) HPT process

Steps during ARB processing


Material
Material by accumulative roll bonding

Twin-roll cast AA5754 and AA1199

Direct-Chill Casting

tandem hot-rolling

scalping & homogenization

annealing

7 - 9 mm

600 mm ingot

cold-rolling

break-down mill

Twin-Roll Casting

The technology based on TRC is much shorter, i.e., energy and cost effective.

annealing

t = 5 - 9 mm

0.1 -0.006mm

cold-rolling


Processing of large coils
Processing of large coils by accumulative roll bonding

AA 1199 - pure aluminium 99.9%


Experimental methods
Experimental methods by accumulative roll bonding

Knoop microhardness

KHN = F/A = 10*F/CL2 Where:F = applied load in NA = the unrecovered projected area of the indentation in mm2L = measured length of long diagonal of indentation in mmC = 0.07028 = Constant of indenter relating projected area of the indentation to the square of the length of the long diagonal.


0.15mm by accumulative roll bonding

0.3mm

procedure of hardness measurements

Knoopmicrohardness as a function of distance from the surface of the sample after 3 ARB steps


Electrical resistivity ( by accumulative roll bonding ) measurements

Standard four-point method in liquid nitrogen during isochronal step-by-step annealing with the step 20K/20min

R, resistance in Ω,

f, form factor in m,

L, the length of the specimen in m,

S, the section in m2

Relative resistivity changes


Microstructure observations by accumulative roll bonding

The light optical microscope NIKON – EPIPHOT 200

Electron microscope JEOL JEM 2000FX

with JEOL single-tilt heating stage


Initial microstructure after ARB processing by accumulative roll bonding

5

1

3

4

5

2


TEM by accumulative roll bonding

Al

Mg

Mg

1

Al

Mg

2

interface


Al by accumulative roll bonding

Mg

Mg

3

Al

Mg

Mg

4


5 by accumulative roll bonding

Al

Mg

Mg

Coarse particles rich in Fe, Mn, Si


Resistivity measurements
Resistivity measurements by accumulative roll bonding


Knoop microhardness
Knoop microhardness by accumulative roll bonding


Average knoop microhardness
Average Knoop microhardness by accumulative roll bonding


Only moderate changes of resistivity below 350 °C followed by significant resistivity increase

Fast drop of microhardness only between 120 and 350 °C


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