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Microctructural study of LM-25

GUIDED BY PRESENTED BY AJIMSHA J M NIHAS NASSIR ASST. PROFESSOR S7 ME MESITAM M 12U036

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CONTENTINTRODUCTIONCHEMICAL COMPOSIONSAMPLE PREPARATIONSEMPARTS AND WORKING OF SEMAFMPARTS AND WORKING OF AFMCOMPARISON STUDYADVANTAGE OF LM-25CONCLUSIONREFERENCES

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INTRODUCTION

•LM 25 is an alloy of Aluminum combined mainly with 6- 7.5 % silicon , 0.2% copper and other materials . •It is corrosion resistant and strong •Excellent weldability •Application ranges from marine, electrical, automobile , nuclear and Aerospace industries .•This seminar deals with properties of the material and microstructure of material using SEM & AFM.

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CHEMICAL COMPOSITION

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Sample preparation

600g of LM -25 were taken and melted in electrical resistance furnace

N2 is used as a degasserGraphite rod are used for stirringPour into the mould and cast is obtainedThis is used as the sample

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Scanning Electron Microscopy

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SCANNING ELECTRON MICROSCOPE (SEM)A scanning electron microscope

(SEM) is a type of electron microscope It images a sample by scanning it with a

high-energy beam of electrons in a raster scan pattern.

The electrons interact with the atoms of the sample

It gives the information about the structures of grain, composition, and other properties

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Components of SEMElectron gunCondenser LensAperture Scanning systemSpecimen Chamber

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AFM

Atomic Force Microscopy

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Parts of AFMLaser – deflected off cantileverMirror –reflects laser beam to

photodetectorPhotodetector –dual element

photodiode that measures differences in light intensity and converts to voltage

Amplifier Register Sample Probe –tip that scans sample made

of SiCantilever –moves as scanned

over sample and deflects laser beam

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Contact ModeNon-Contact ModeTapping

(Intermittent contact) Mode

3 MODES OF AFM

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Contact modeMeasures repulsion between tip and sample.Force of tip against sample remains constant.Feedback regulation keeps cantilever deflection

constantProblems: excessive tracking forces applied by

probe to sample

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Non contact modeMeasures attractive forces between tip

and sampleTip doesn’t touch sampleVan der Waals forces between tip and

sample is decteced and gives the AFM image

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Tapping modeTip vertically oscillates between the

sample surface at a frequency of 50,000 to 500,000 cycles/sec.

Oscillation amplitude reduced as probe contacts surface due to loss of energy caused by tip contacting surface. And gives the AFM image of the test specimen.

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property LM-25 Aluminium SteelDensity 2670 kg/m3 2730kg/m3 7750kg/m3

Melting Point 615°C 660.3°C 1370°C

Elastic Modulus

71 GPa 70.0GPa 190.3GPa

Tensile strength

280 mpa 714.0 mpa 500 mpa

Percent Elongation

5% 20% 17%

Hardness 120 BHN 100BHN 95 BHN

COMPARISON STUDY

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Advantages of LM-25

good corrosion resistance • Excellent cast ability • It is corrosion resistant and strong • Excellent weldability • Application ranges from marine,

electrical, automobile , nuclear and Aerospace industries

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product made from LM-25

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CONCLUSIONThe micro structural studies shows that LM-

25 posses good corrosion resistance and mechanical properties

Posses excellent weldability It found more application in the field of

marine, electrical, automobile , nuclear and Aerospace industries

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References

[1] Association of North America 1998, pp1-31[2] T.V.S. Reddy, D.K. Dived, N.K. Jain, Adhesive wear of

stir cast hypereutecticAl–Si–Mg alloy under reciprocating slid in conditions, Wear 266 (2009) 1–5.

[3] J. Clarke, A. D. Sarkar, Wear characteristics of as-cast binary aluminiumsilicon alloys, wear, 54 (1979) 7 – 16.

[4] Toni Bogdan off and Jimmy Dahlstrom,The influence of copper on an Al-Si-Mg alloy (A356) - microstructure and mechanical properties, school of engineering, Jonkoping University, june-2009, pp 10.

[5] K.B. Shah, Sandeep Kumar and D.K.Dwived, Aging temperature and abrasive wear behavior of cast Al– (4%, 12%, 20%)Si–0.3% Mg alloys,Dec 2004.