Fine Micro Extrusion

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Micro extrusion of ultra finegrained aluminium.

BYAndrzej Rosochowski &Wojciech Presz & Lech Olejnik & MariaRichert

(International Journal of Advance Manufacture Technology(2007))

Presented by-

NITIN DWIVEDI(20063008)RAHUL PEDAPUDI(20063062)


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AIM

Backward extrusion is carried out for two types of

material, CG and UFG aluminium. Their behavior and

mechanical properties are compared to decide which

is best for the micro parts.

The author has manufactured a cup of followingdimensions to study the properties:

external dia : 1.80mm

internal dia : 1.24mm

height : 1.30mm

depth : 1.05mm


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What is Fine Micro-Extrusion?

Micro forming is understood to be the productionof parts or structures with at least two dimensions

in the sub-millimeter range. Micro forming ofnormal, coarse grain (CG) metals leads to scaleproblems which originate from the fact that thegrain size becomes comparable to the part size. A

possible way of dealing with these problems isreplacing CG metals with ultra-fine grained (UFG)metals. UFG metals can be produced in bulk bysevere plastic deformation (SPD).


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INTRODUCTION

Ultra-fine grained (UFG) metals produced byeither powder metallurgy or severe plasticdeformation (SPD). The powder metallurgyroute, which involves Nano powders, enablesobtaining grains smaller than 0.1 m. However,the cost, residual porosity and health issues arethe known concerns for this route. SPD, which is

based on inducing a very large plasticdeformation without basically changing theshape of the billet, can reduce the original grainsize of the material to approximately 0.11 m.


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Obtaining UFG Aluminium

1)UFG MetalsVery high yield and ultimate strength.

Reasonable ductility.

High impact strength at low temperatures.Super plastic at elevated temperatures.

Existing applications of UFG metals are inmedical transplants, structural parts forautomotive and aerospace industries,defense systems and sports equipments.


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Nanostructuring of Aluminium by SPD

There are numerous SPDprocesses, which areused on a laboratoryscale. There are no

industrially accepted SPDprocesses as yet. Themost popular SPDprocess is equal channelangular pressing (ECAP).

It is based on forcing ametal billet through an L-shaped channel ofconstant profile (usuallysquare or round).


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a) The initial shape of the billet

b) Partially extruded billet

c) Billet after leaving the die


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Mechanical properties of CG and UFG aluminium

1070

The material used was commercially pure aluminium 1070. It wassupplied in the form of a hot extruded round bar, 38 mm in diameter.

Metallurgical testing showed that the initial average grain size was

approximately 500 m.After three consecutive passes through a 3D-ECAP die, the amount of

plastic strain generated in the material reached 10.35. Such a large

strain led to grain refinement with the average grain size of 0.2 m


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Table 1:Mechanical properties of CG and UFG aluminium 1070

Material

grade

Yield

strength

Re (MPa)

Ult imate

Tensile

strength

Rm(MPa)

Elongat ion

To fractu re

A5 (%)

Area

reduct ion

at fractu re

Z (%)

CG Al 56 73 39 97

UFG Al 173 188 16 72


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Step 1:Producing plates for blanking


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Step 2:Blanking of Billets

1. Plate

2. Die

3. Blank holder

4. Punch

5. Blank

S Cl d d d B k d f


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Step 3 :Closed die compression and Backward extrusion of

Micro-cup

1. Blank

2. Die

3. Cylindrical support

4. Pressing punch

5. Punch guide

6. Support plate

7. Base plate


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Punches used in various steps

Tip of punch used for backward extrusion


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Blanking force for CG and UFG aluminium

a, b Extruded aluminium cups a CG b UFG


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Parameters of the multi stage forming process used formanufacturing of micro cups

Forming process Punch velocitymm/min) Tool diameter mm)Punch DieBlanking with blankholder

1 1.60 1.67

Close die compression 0.1 1.60 1.80

Backward extrusion 0.1 1.24 1.80


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Characteristics of Extruded Cup

UFG Aluminium CG aluminium


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HARDNESS


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CONCLUSION

UFG metals seems to be a better option for micro

forming.

More uniform structure, better shape representation andenhanced properties of micro parts.

More uniform flow of the material and suggested a better

shape capability.


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Fine Micro Extrusion

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