Plastic Deformation of Aluminum Alloy-6082

By: kalyan kumar dhar

Information of the Sample :

?Sample features:

?Aluminum alloy 6082 is a medium extrudability, high strength, structural alloy with good toughness and corrosion resistance.??????

?The material used in this study was a commercial Al-mg-Si alloy (AL-6082).the main components of the alloy are al (97%) , Si (0.7%-13%), mg (0.6-1.2%).some char arties properties of aluminum alloy 6082? are listed below :

Composition:

Al 0.9Mg 1.0Si 0.7

Applications:

Heavy duty structures in rail coaches, truck frames, ship building, offshore, bridges, military bridges, bicycles, boiler making. Machinery: platforms, flanges, hydraulic systems, mining equipment, pylons and towers, motorboats. Nuclear technology. Masts and beams for ship building (especially for sweet water). Tubes for scaffolding, framework for tents and halls, piping, tubing Screw machine products. Rivets.

Characteristic Properties:

Very good corrosion resistance. Very good weld ability (lowered strength values in the zone of welding). Good mach inability. Good cold formability in T4 temper after a stabilizing heat treatment. Heat treatable medium high strength construction. Alloy with a strength somewhat higher than 6061. Medium high fatigue strength. Not suitable for complex sections.

Product Forms:

?Sheet, Bar, Wire, Tube, Profile section shape, Forging, Slugs impacts

As a result of its versatile combination of properties, alloy 6082 is widely used in structural applications in the building, marine and transport industries as well as for machined parts in the automotive industry.

Virtual Experiment:

The original thickness of plate (aluminum alloy)we are using during our experiment is 10 mm .In our experiment? we are going to check the different structure of grain boundary as well as different hardness due to change the Materials properties of the Al-alloy.

Outline: firstly we need to prepare samples with a range of different thickness'. we did this by deforming (rolling ) a plate by different amounts ,cutting samples at each stage . we then annealed the samples to fully re-crystallized them. Polishing is required and also polishing is the important part to find the grain microstructure .so attention as well as caution is necessary during polishing process of the sample.

?Heavily deformed samples should re-crystallized to give a finer grain size .

After measuring the Thickness , we did Vickers hardness measurements on each ,and collected the Micrograph of the grain boundary of each of our supplied sample .

The different experimental technique are described bellow:

Cutting machine : we used cutting machine in order to acquire the desired shape of the materials which is suitable in our hot as well as cold rolling machine .

Heat treatment process: Heat we also used the heat treatment process which is also play an effective role in our experiment . In this process we maintain the temperature at about 450 degree Celsius . we used oven to supply heat.

A. Oven : we use oven as a part of our experiment . caution should me maintain during the using of oven . Because the temperature is very high. Aluminium alloy i.e. our sample put into oven due to acquire as? well as to use this materials in hot rolling procedure.

B.Annealing. :

Before deformation the materials was annealed on 450 degree Celsius for almost 60 minute .Specimens ?in this condition were regarded as received material. Due to internal stored energy, the cold worked microstructure is a met stable state as it will try and reduce its internal energy. Usually this process is enabled by annealing the worked material. Micro structural changes depend on temperature and time of anneal and, heating rate.

During this short anneal, the deformed grains re -crystallize via a nucleation and growth process to form a new set of relatively dislocation -free grains .the size of the re-crystallized grains will be determined to a large extent by the amount of prior deformation , i.e. the %reduction during rolling

Deformation process:

1.?????? cold process (room temperature ).

2.?????? hot rolling process(temperature is 450 degree Celsius)

Experimental Data:

Initial plate thickness, t0?=?10 ?mm

plastic deformation, or work hardening, of metals increases the dislocation density. Dense dislocation 'tangles' can form, obstructing the movement of other dislocations.

Alloy elements, such as Mg, Mn and Cu can 'pin' dislocations, thereby strengthening the material.
Small, finely dispersed precipitates can significantly increase the strength of aluminum alloys.

Grain size hardening

Reducing the grain size increases the alloy strength according to the Hall-Petch relationship.

Grain boundaries in our experiment we got different experimental value as well as different thickness and hardness due to change of the properties ?of the materials. We also know from the definition of hardness? as "Resistance of metal to plastic deformation, usually by indentation. However, the term may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting. It is the property of a metal, which gives it the ability to resist being permanently, deformed (bent, broken, or have its shape changed), when a load is applied. The greater the hardness of the metal, the greater resistance it has to deformation.

?The dictionary of Metallurgy also defines that ?the indentation hardness as the resistance of a material to indentation. This is the usual type of hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. The effect of grain size is also very strong on hardness and strength. The smaller the grain size, the higher the strength and hardness according to the well known Hall-Petch relationship:

This relationship can be explained assuming that grain boundaries act as obstacles to slip of

dislocation, causing them to pile up on their slip planes against boundaries.

Grain boundaries separating grains of the same structure with a limited disorientation (low-anglegrain boundaries, LAGBs) can be considered as arrays.

Although grain boundaries are clearly visible even on low magnification micrographs (due to

etching), their actual width is very small. Therefore, it can be stated that grain boundaries do not posses long-range stress fields.

So plastic deformation process which can produce high strength metals with ultra-fine grained microstructure. Mechanical properties will be increased due to the ultra-fine grain structures.

?It is also well known that precipitation of most secondary phases and embrittling phenomena occur at grain boundaries. Hence, the amount of grain boundaries and their condition/reactivity is of great importance for micro/macroscopically properties of polycrystalline metals.

plastic deformation (PD) is currently one of the most promising methods for processing ultra fine microstructures. Ultra fine-grained materials generally offer high strength coupled with reasonably good fracture toughness and often super plastic properties at moderate temperatures and at high strain rates
.Especially, the low-strength commercially pure and low-alloyed metals can be dramatically enhanced by extensive grain refinement, thus offering new opportunities to exploit some attractive physical properties in metals having a reasonably high strength for structural
applications.

?For instance it is known that at low temperatures, these are normally quite strong and the metal fails by cracks that develop at grain interiors (Tran granular fracture). At high temperatures and slow strain rates, the grainboundaries lose their strength more rapidly than the crystal, fracture can occur through the grainboundaries (intergranular failure).

The numerous investigations of recent years show that grain boundaries play an important role in providing mechanical and physical properties of aluminium alloy-6082. however their influence is not unique and depends on features of crystallographic structure ,long range areas of grain boundaries and their changes caused by external effects .
For example grain refinement results in an improvement of mechanical properties that is exposed by well know Hall-patch relationship?.

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