heat treatment and its effect on extrudability of aa6063

INTRODUCTIONThe 6xxx series alloys are mainly used in extrusion industry. The AA6063 alloy finds application in architectural

items, railings, pipes, floorings of automobile buses and trucks, windows. The chemical composition of typical 6063 alloy has 0.2-0.6% Si, 0.45-0.9% Mg, .35% Fe max., 0.1% Mn max. , 0.1% Zn max. , 0.1% Ti max. , 0.05% other max. (Each) and 0.15% other (total) with balance Aluminium.HOMOGENIZATION AND EXTRUDATE QUALITY

The billets that are used in Extrusion are mainly Direct Chill casted and has cored and heterogeneous dendriticmicrostructure. Fe is present in the aluminium as impurity and since it has low solid solubility in Aluminium , it forms intermetallic compoundswith Al along Si. The Fe containing intermetallics are formed during solidification along the boundaries of dendrites. [1] The as cast structureshave inferior workability because of low ductility of intergranular and interdendritic network of second phase particles . The main Fe containingintermetallics are β-AlFeSi which has plate type morphology and α-Al(FeMn)Si which has Chinese script type morphology.[The β-AlFeSi interfaceis sharper and hence it can cause local crack initiation which affects the quality of surface produced during extrusion. On the other hand α-Al(FeMn)Si particles are more rounded and has diffused interface with Al matrix.[2] Homogenization of Aluminium is essentially a heattreatment before extrusion which equalises concentration differences within dendritic arms. The transformation of plate like β-AlFeSi takesplace into more rounded α-Al(FeMn)Si particles.[3] Mg2Si dissolves quickly into solid solution so it is the β to α transformation that decides theduration of homogenization treatment.

EFFECT OF HOMOGENIZATION TREATMENT AT VARIOUS TEMPERATURES ON EXTRUDABILITY OF AA6063 ALLOY

Ninad V. Pawar (MT14MTE011)Project Guide: Dr. D.R.Peshwe,(H.O.D.) Mr. R.N.Chauhan (Scientist-III) Department of Metallurgical & Materials Engineering, V.N.I.T Nagpur J.N.A.R.D.D.C. , Nagpur

EXPERIMENTAL PROCEDURE

Samples of size 30mm×30mm×15mm were cut from a 7”diameter DC Cast billet and then heated to 580°C for 2, 4, 8 and 12hours and water quenched. The optical and SEM images were taken forAs-Cast and Homogenised samples. The Image Analysis was done withhelp of ImageJ software for particle circularity. The particles at grainboundaries were analysed for circularity.

EXPERIMENTAL PLAN1. Homogenization at different temperatures- 520°C- 600°C for

2, 4, 8, 12, 24 and 30 hours followed by water quenching.2. Optical and Scanning Electron Microscopy3. Image Analysis – Circularity of particles and its frequency

distribution for each time and temperature combination4. EDS analysis

- Change in Si content with respect to time and temperature.- Change in Fe;Si ratio

RESULTS

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8HR-580°C

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12HR-580°C

Fig.01 As Cast Microstructure at 500X Fig.02. Homogenised for 2 hrs at 580°C

Fig.03. Homogenised for 4 hrs at 580°C Fig.04. Homogenised for 8 hrs at 580°C

Fig.05. Homogenised for 12 hrs at 580°C

Fig.06. SEM micrograph of As Cast structure

Fig.07. SEM micrograph of homogenised sample for 8hrs at 580°C

REFERENCES1. H.Tanihata et.al. journal of Materials Science

34(1999)1205-12102. N.C.W.Kuijpers et.al, Mat.Trans. Vol. 44. No.7

(2003)1448-14563. S.R.Claves et.al., Materials Science

Forum, Vol.396-402 (2002) 667-6744. S.Onurlu, A.Tekin, Journal of Materials Science

29 (1994) 1652-16555. A.Verma et.al. Journal of Alloys and

Compounds 555 (2013) 274-2826. S.Zajac et.al ,Material Science and

technology, Vol.10 (1994) 323-3337. George Totten, Handbook of

Aluminium, Vol.I, Marcel Dekker Inc.8. John E. Hatch , Aluminum Properties and

Physical Metallurgy,9. Terry Shepherd, Extrusion of Aluminium

Alloys, Springer Science

CIRCULARITY

CIRCULARITYCIRCULARITY

CIRCULARITY

CIRCULARITY