Procedia Engineering 97 ( 2014 ) 1676 – 1682

1877-7058 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014doi: 10.1016/j.proeng.2014.12.318

ScienceDirectAvailable online at www.sciencedirect.com

12th GLOBAL CONGRESS ON MANUFACTURING AND MANAGEMENT, GCMM 2014

The Effect of Heat Treatment and Aging Process on Microstructure and Mechanical Properties of A356 Aluminium Alloy Sections in

Casting

K.T. Akhila,*, SanjiviArulb, R.Sellamuthuc aPG Scholar,Dept. of Mech. Engg., Amrita VishwaVidyapeetham,Coimbatore-641112-India,akhilkt9@gmail.com

bAssoc. Professor,Dept. of Mech. Engg., Amrita VishwaVidyapeetham,Coimbatore-641112-India,s_arul@cb.amrita.edu cProfessor,Dept. of Mech. Engg., Amrita VishwaVidyapeetham,Coimbatore-641112-India,r_sellamuthu@cb.amrita.edu

Abstract

Aluminium A356 alloy is widely used at automobile and aircraft industries in the form of cast component with varying section size. This study investigates how the microstructure and mechanical properties of different section size vary before and after heat treatment and aging processes. Aluminium ingot is melted using a furnace and poured in to the mold having mold cavities of varying dimensions. Cast components are heat treated as per ASTM standard B917-01 at a temperature of 537°C for 12 hours followed by a temperature of 155º for 5 hours. In order to investigate the effect of heat treatment and aging processes microstructure and mechanical properties such as impact strength, hardness, and tensile strength were analysed as-cast condition and after heat treatment and aging process. © 2014 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014.

Keywords:Aluminium A356 alloy, microstructure, impact strength, hardness, tensile strength, metal casting, heat treatment, and aging.

1. Introduction

Cast A356 aluminum alloy is widely used in automotive and aircraft industries because of their excellent properties like high strength to weight ratio, low density, high corrosion rates etc. This increased use of A356 aluminum alloy leads to a need for deeper understanding of their mechanical properties and the impacts of

* Corresponding author. Tel.:+91 9496285256.

E-mail address:akhilkt9@gmail.com

© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of GCMM 2014

1677 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

processing factors [1-2, 4]. The mechanical properties can determine by controlling the microstructures of the alloys. For designing any part we should have a thorough understanding of solidifications at different cross sections of the cast part and its influence on the mechanical properties [5-6, 3].Most applications of A356 alloy dependent on mechanical properties, so the performance of this alloy has been the subject of many micro-mechanical investigations. Mechanical properties were improved with grain refinement. Since the mechanical properties are mainly dependent on their microstructure, a lot of efforts have been done for refining microstructure of casting to improve the mechanical properties of aluminum alloy A356. Refinement can achieve by using power ultrasound and electromagnetic stirring and equal channel angular pressing, or accumulative roll bonding. As-cast A356 alloys are made up of coarse primary α-Al dendrites and acicular-shaped eutectic silicon, which lowers the mechanical properties and limits its industry application. Heat treatment and aging are important to homogenize α-Al dendrites in aluminum alloys so we can achieve better mechanical properties. Cooling rate of mold is measured by introducing a thermocouple inside the mold [7-8]. Heat treatment and aging processes are the most important processes determining casting microstructure and mechanical properties [1- 2, 11- 12]. As-cast A356 alloys are made up of coarse primary α-Al dendrites and acicular-shaped eutectic silicon, which lowers the mechanical properties and limits its industry application. The mechanical properties can determine by controlling the microstructures of the alloys [9-10]. Heat treatment and aging are important processes to homogenize α-Al dendrites in aluminium alloys [11].

2. Experimental method

Experimental apparatus consisting of four green sand molds with mold cavities of 20 mm, 40 mm, 60 mm, 80 mm diameters (section sizes). A356 aluminum alloy is melted using muffle furnace and poured to the molds. Thermocouple tip is placed 1mm apart from mold cavity in order to avoid damage of contact tip and temperature is monitored till there is a decrease in temperature after an initial increment. Temperature is measured using a K type thermocouple. Temperature-Time graph were plotted for all experiments and cooling rate for each sections were measured. Cast specimens were heat treated to ASTM standard B917-01 at a temperature of 537°C for 12 hours and followed by an aging of 5 hours.

3. Testing

In order to investigate the effect of heat treatment and aging process on microstructure and mechanical properties, impact strength, hardness and tensile strength were measured for as-cast condition, heat treated and aged condition. Specimens were prepared for microstructural analysis by polishing on disc polisher followed etching with diluted hydrofluoric acid. Microstructural analysis was performed by an inverted metallurgical microscope and the microstructures were compared. Average grain size is measured using Metal Vision software. Cast specimens were machined to ASTM standard E23-12C, 10 mm*10 mm*75 mm for Izod test and 10 mm*10 mm*55 mm for Charpy test. Using an impact testing machine model IT30 both impact tests Izod test and Charpy test were performed for as cast condition and heat treated and aged condition. Cast specimens were machined to ASTM standard E8M with a gauge length of 45mm and gauge diameter of 9mm for tensile test. Tensile test were performed on universal tensile testing equipment and ultimate tensile stress value for as-cast condition and after heat treated and aged condition were compared. Hardness test were performed with Vickers hardness tester by applying a load of 100kgf for 20 second both as cast condition and after heat treated condition. All tests were repeated 5 times in both as-cast and aged and heat treated condition.

4. Results and discussion

4.1. Effect of section size on cooling rate

Fig. 1 shows cooling curves of cast specimens of varying section size. Time taken to decrease in temperature for 20 mm, 40 mm, 60 mm, 80 mm, sections were 15 minutes, 22 minutes, 27 minutes, 31 minutes respectively. Cooling rates are measured from the graph and found to be 40C/minute, 30C/minute, 20C/minute and 10C/minute for

1678 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

20 mm, 40 mm, 60 mm, and 80 mm sections respectively. From the graph it is found that increasing the section size lead to reduction of cooling rate or increase in solidification time.

Fig. 1. Cooling Curves of cast components with varying section size

4.2. Microstructure evaluation

(a) (b)

(b) (d)

Fig. 2. Change in microstructureof as cast specimens with variation in section size (Magnification 200X)

(a) 20 mm, (b) 40 mm, (c) 60 mm, (d) 80 mm

Fig. 2 shows change in microstructure of as-cast specimens with variation in section size and Fig 3 shows changes in microstructure of heat treated and aged cast specimens. As-cast condition microstructure is found fine for small section size and coarse for large section size this is due to grain refinement of smaller section size caused by fast cooling rate. Microstructure is found much refined and uniform in all section size for heat treated and aged condition. Fig. 4 shows as-cast, heat treated and aged conditions Grain size variation with section size. As-cast condition average grain size was found to be 0.82 microns, 0.94 microns, 1.4 microns, 1.8 microns for 20 mm, 40

1679 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

mm, 60 mm, 80 mm sections respectively. It shows an increase in average grain size with increasing section size due to reduction in cooling rate. Average grain size for heat treated and aged condition was found to be 0.52 microns, 0.59 microns, 0.56 microns, 0.58 microns for 20 mm, 40 mm, 60 mm, 80 mm sections respectively. At heat treated and aged condition average grain size is much less compared to as-cast condition but it is almost constant with variation in section size.

(a) (b)

(c) (d)

Fig. 3. Changes in microstructure of heat treated and aged cast specimens with variation in section size (Magnification 200X)

(a) 20 mm, (b) 40 mm, (c) 60 mm, (d) 80 mm

Fig.4. Variation in Grain size with section size.

1680 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

4.3. Impact test evaluation

Fig. 5 shows as-cast, heat treated and aged conditions impact strength variation with section size. As-cast condition impact strength in Charpy test is found 67.42 KJ/m2, 60.22KJ/m2, 55.43KJ/m2, 48.31 KJ/m2 for 20 mm, 40 mm, 60 mm, 80 mm size having sections and Impact strength in Izod test is found 69.61 KJ/m2, 62.28 KJ/m2, 54.96 KJ/m2, 47.63 KJ/m2 for the same section respectively. It indicates that as-cast condition impact strength increase with reduction in section size. This is due to grain refinement in smaller section size caused by fast cooling rate. Heat treated and aged condition impact strength in Charpy test is found 114.0 KJ/m2, 109.0 KJ/m2, 111.57 KJ/m2, 116.5 KJ/m2 for 20 mm, 40 mm, 60 mm, 80 mm size having sections and Impact strength in Izod test is found 113.5 KJ/m2, 109.8 KJ/m2, 113.5 KJ/m2, 106.12 KJ/m2for the same section respectively. Impact strength at heat treated and aged conditions were improved comparing as cast condition but it is almost constant with variation in section size. This is due to much higher grain refinement in heat treated and aged condition irrespective to section size.

Fig. 5 Variation in Impact strength with section size

4.4. Tensile test evaluation

Fig. 6 shows as-cast, heat treated and aged conditions Ultimate Tensile Stress of all cast sections. As-cast condition Ultimate Tensile Stress is found 145.4 MPa, 142.9 MPa, 70.4 MPa, 60.1 MPa for 20 mm, 40 mm, 60 mm, 80 mm size sections respectively. It is found that as-cast condition Ultimate Tensile Stress is increased with reduction in cast component section size. This is due to grain refinement in smaller section size caused by fast cooling rate. Heat treated and aged condition Ultimate Tensile Stress is found 263.5 MPa, 269.3 MPa, 265.2 MPa, 258.1 MPa for 20 mm, 40 mm, 60 mm, 80 mm size sections respectively. Ultimate tensile strength at heat treated and aged condition was improved compared to as-cast condition but it is almost constant with variation in section size. This is due to much higher grain refinement in heat treated and aged condition irrespective to section size.

1681 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

Fig.6. Variation in Ultimate tensile stress with section size

4.5. Hardness test evaluation

Fig. 7 shows as-cast, heat treated and aged conditions hardness of all sections. As-cast condition Micro hardness is found 82.6 HV, 78.3 HV, 75.2 HV, 70.4 HV for 20 mm, 40 mm, 60 mm, and 80mm size having sections respectively. It indicates that Micro hardness of as-cast components increases as section size decreases. This is due to grain refinement in smaller section size caused by fast cooling rate. Heat treated and aged condition hardness is found 112.6 HV, 122.6 HV, 117.5 HV, 114.2 HV for 20 mm, 40 mm, 60 mm, and 80 mm size having sections respectively. Heat treated and aged condition hardness was improved compared to as-cast condition but it is almost constant with variation in section size. This is due to much higher grain refinement in heat treated and aged condition irrespective to section size.

Fig. 7. Variation in Hardness with section size

1682 K.T. Akhil et al. / Procedia Engineering 97 ( 2014 ) 1676 – 1682

5. Conclusion

As-cast condition Mechanical properties such as impact strength from 48.31 KJ/m2 to 67.42 KJ/m2, Ultimate Tensile Stress from 60.1 MPa to 145.4 MPa, Hardness from 70.4 HV to 82.6 HV were increased with decreasing section size from 80 mm to 20 mm due to grain refinement. Heat treated and aged condition mechanical properties such as impact strength, ultimate tensile stress, hardness were further improved but it is almost constant with variation in section size. This is due to further grain refinement in heat treated and aged sections irrespective to section size.

References

[1] H. Abu EI-Aini, K. Mohamed, Y. Hassan Mohammed, Effect of mold types and cooling rate on mechanical properties of Al alloy 6061 within ceramic additives, The 2nd International conference on Energy engineering, ICEE-2, ( 2010) 27-29. [2]G. Mrwka–Nowotnik, J. Sieniawski, M. Wierzbiska, Analysis of intermetallic particles In AlSi1MgMn aluminium alloy, J of Achievements in Materials and Mfg Engg, 20 (2007)155-158. [3] A. Boschetto, G. Costanza, F. Quadrini, M. E. Tata, Cooling rate inference in aluminium alloy squeeze casting, Materials Letters, 6 (2007) 2969-2972. [4] Z. Li, M. Samuel, F. Samuel, C. Ravindran, S. Valtierra, H.W.Doty, Parameters controlling the performance of AA319-type alloy, Materials Science and Engineering, 367( 2004) 96-110. [5] S. G. Shabestari, H. Moemeni, Effect of copper and solidification conditions on the microstructure and mechanical properties of Al–Si–Mg alloys, Journal of Materials Processing Technology, 153-154 (2004) 193-198. [6] J. H. Lee, H.S. Kim, C. W. Won, B. Cantor, Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing, 338 (2002) 182–190. [7] C. H. Caceres, C. J. Davidson, R. Griffiths, The deformation and fracture behaviour of an Al–Si–Mg casting alloy, Materials Science and Engineering, 197 (1995) 171–179. [8] P. S. Mohanty, J. E. Gruzleski, Grain refinement mechanisms of hypoeutectic Al–Si alloys, Acta Mater, 44 (1996) 3749–60. [9] S. A. Kori, B. S. Murty, M. Chakraborty, Preparation and characterization of Al–B and B-rich Al–Ti–B master alloys for the grain refinement of Al–7Si alloy AFS Trans 109 (2001) 267–86. [10] D. L. Zhang, L. Zheng, The quench sensitivity of cast Al–7 wt.%Si–0.4 wt.%Mg alloy. Metall Mater Trans, 27 (1996), 3983–91. [11]E. Ogris, A. Wahlen, Luchinger, P. J. Uggowitzer, On the silicon spheroidization in Al–Si alloys. J Light Metals, 2 (2002) 263–9.

TUGAS PROSES MANUFAKTUR DAN PEMILIHAN MATERIAL

MARDIANSYAH PRATAMA (1406533094)

TRIANA YUSMAN (1406533081)

DEPOK, 18 FEBRUARI 2016

TUGAS 1

JAWABAN SOAL

1. What are the condition for obtaining substitutional and interstitial solid solution?

(a) Substitutional solid solutions : Terjadi jika zat pelarut atau atom mayoritas dalam pola-pola

geometris digantikan posisinya oleh zat terlarut. Sebagai contoh atom tembaga menggantikan

posisi atom-atom nikel tanpa mengganggu struktur pola geometris nikel itu sendiri. Syarat

terjadinya Substitutional solid solution adalah:

- Kedua atom mempunyai struktur kristal yang sama

- Perbedaan jari-jari atom keduanya harus kecil dari 15 persen

(b) Interstitial solid solutions : Atom zat pelarut tidak digantikan posisinya oleh atom zat terlarut,

tapi atom zat terlarut mengisi ruang di celah-celah diantara atom-atom zat pelarut. Syarat

terjadinya Intertitial solid solution adalah:

- Solvent mempunyai valensi yang lebih dari satu

- Jari-jari atom solute kecil dari 59 persen dari jari-jari atom solvent

2. Descibe the major features of a phase diagram!

The major feature of a phase diagram : yaitu sebuah representasi grafis dari keseimbangan suhu

dan komposisi batas reaksi bidang fase dalam sistem paduan. Dalam sistem biner, suhu biasanya

ordinat dan komposisi absis. sistem terner dan lebih kompleks memerlukan beberapa diagram

dua dimensi untuk menunjukkan suhu - variabel komposisi sepenuhnya. Dalam sistem paduan,

tekanan biasanya dianggap konstan, meskipun mungkin diperlakukan sebagai variabel tambahan.

keunggulan diagram fase adalah menunjukan fase antara paduan, menghubungkan hubugan

temprature dengan karakteristik paduan, dan menunjukan titik ekuilibrium pada suatu paduaan.

Phase boundaries or lines of equilibrium: suatu garis dimana dua buah fasa bertemu pada

kondisi setimbang

Triple point: suatu titik dimana tiga buah fase bertemu dalam garis kesetimbangan (gas,

cair, padat)

3. What do the term equilibrium and constitutional as applied to phase diagram, indicate?

(a) Ekuilibrium : Yaitu Sebuah kondisi dinamis keseimbangan antara gerakan atom, di mana

resultan adalah nol dan kondisi tampaknya menjadi salah satu perhentian daripada perubahan.

(b) Constitusional: yaitu suatu keadaan pada fase diagram yang berhubungan antara kedua

struktur , komposisi, dan struktur properti fisik yang menjadi informasi dalam proses pembuatan

paduan (alloy)

4. What are precipitates? Why are they significant in precipitation hardening?Precipitates :

Yaitu suatu endapan yang tidak larut pada reaksi produk padat ionik, terbentuk ketika kation dan

anion tertentu bergabung dalam larutan cair. Faktor yang menentukan pembentukan endapan

dapat bervariasi. Endapan ini diperlukan untuk meningkatkan kekuatan struktur dari suatu bahan

sebagai yang memberikan ketahanan suhu, dalam hal ini pula endapan diperlakukan dengan

mengatur suhu untuk mendapat kan hal-hal tersebut. Tekniknya adalah dengan mendispersikan

secara seragam partikel kecil dari suatu fasa selain fasa asal ke dalam matriks dari fasa asal.

5. Describe the characteristics of ferrite, austenite, and cementite!

(a) Ferrite : Larutan padatan yang bisa disebut α-Fe. Yang didalam larutannya terdapat karbon

dalam jumlah yang terbatas dalam ukuran B.C.C (body cube cubik) dengan bentuk struktur

menyerupai kristal dengan Fe utuh terletak dipusatnnya.

(b) Austenite: Larutan padatan yang bisa disebut ɣ-Fe. Dimana Fe nya terdistribusi secara

Interestitial dengan karbon menempati secara Interestitial. Hal ini menyebabkan austenite lebih

padat dari pada feritte. Namun austenite hanya akan bersifat ductile apabila pada suhu tinggi ,

sehingga mudah dibentuk pula.

(c) Cementite: Yaitu Besi karbida Fe3C, struktur ini bersifat sangat keras dan struktur ini juga

dipengaruhi oleh karbidanya (sementite) dalam menentukan kekerasnnya.

6. What is the purpose of annealing?

Tujuan utama dari proses annealing adalah untuk mengurangi kekerasan dari baja dan membuat

struktur yang mudah dilakukan proses pemesinan. Selain itu anneling bertujuan untuk

memperbaiki sifat – sifat antara lain:

1.mampu mesin

2.mampu bentuk

3.keuletan

4.kehomogenan struktur

5.menghilangkan tegangan dalam

6.persiapan struktur unutk proses perlakuan panas

7. Decribe the engineering significance of the existence of a eutectic point in phase diagram!

Eutectic point in phase diagram : Titik leleh komposisi hanya pada suhu (suhu eutektik/Te) atau

perpotongan antara kurva likuidus dan garis solidus. Dalam hal ini titik eutektik sangat penting

keberadaannya karna titik ini menunjukkan komposisi kimia dan suhu yang sesuai dengan titik

leleh terendah dari campuran komponen.

8. It generally is not desirable to use steels in their as quenched condition. Explain why?

Dalam hal ini pada dasarnya steel ingin di potong atau di ubah bentuknya dengan cara di

panaskan dengan di panaskan steel akan lebih mudah untuk dibentuk. Namun ketika di dinginkan

atau pada kondisi dingin steel cenderung menjadi lebih mudah untuk getas (rapuh) sehingga steel

akan mudah hancur dan tidak dapat dipakai atau diubah bentuknya. Hal ini lah yang menjadi

alasan mengapa pada umumnya not desirable to use steels in their as quenched condition.

9. Descibe thee characteristics of an alloy, pearlite, eustenite, martensite and cementite!

(a) an Alloy : yaitu suatu campuran/paduan dua atau lebih unsur kimia yang salah satunya adalah

logam. bentuk dasar dari an alloy (paduan) adalah larutan padat dan senyawa intermetalik. kuat,

keras, dan rapuh. Karena titik leleh tinggi, kekuatan pada suhu tinggi, ketahanan oksidasi yang

baik, dan kepadatan relatif rendah, an alloy adalah bahan kandidat untuk aplikasi seperti mesin

turbin gas. Seperti Aluminides of titaniu (〖Ti〗_3 Al), nikel (〖Ni〗_3 Al), and iron (〖Fe〗

_3 Al).

(b) Pearlite : Pearlite is a tw-phased, lamellar (or layered) structure composed of alternating

layers of ferrite (88 wt%) and cementite (12 wt%) that occurs in some steels and cast irons. In

fact, the lamellar appearance is misleading since the individual lamellae within a colony are

connected in three dimensions; a single colony is therefore an interpenetrating bicrystal of ferrite

and cementite. In an iron-carbon alloy, during slow cooling pearlite forms by a eutectoid reaction

as austenite cools below 727 °C (1,341 °F) (the eutectoid temperature). Pearlite is a

microstructure occurring in many common grades of steels.

(c) Austenite : Larutan padatan yang bisa disebut ɣ-Fe. Dimana Fe nya terdistribusi secara

Interestitial dengan karbon menempati secara Interestitial. Hal ini menyebabkan austenite lebih

padat dari pada feritte. Namun austenite hanya akan bersifat ductile apabila pada suhu tinggi ,

sehinnga mudah dibentuk pula.

(d) Martensite : Martensit terbentuk pada baja karbon dengan pendinginan cepat (quenching) dari

austenit pada kecepatan yang tinggi dalam atom karbon sehingga tidak punya waktu untuk

berdifusi keluar dari struktur kristal dalam jumlah cukup besar untuk membentuk sementit

(Fe3C). Akibatnya, austenit kubik berpusat muka berubah ke bentuk berpusat badan yang sangat

tegang tetragonal dari ferit yang jenuh dengan karbon. Deformasi geser yang dihasilkan

menghasilkan dislokasi, yang merupakan mekanisme penguatan utama baja. Kekerasan tertinggi

dari baja perlitik adalah 400 Brinell sedangkan martensit dapat mencapai 700 Brinell. Salah satu

perbedaan antara dua fase adalah bahwa martensit memiliki struktur kristal Body-Centered

tetragonal (BCT), sedangkan austenit memiliki struktur Face-Centered Cubic (FCC).

(e) Cementite : Yaitu Besi karbida Fe3C, struktur ini bersifat sangat keras dan struktur ini juga

dipengaruhi oleh karbidanya (sementite) dalam menentukan kekerasnnya.

10. Explain why carbon, among all elements, is so effective in imparting strenght to iron in

the form steel?

Karena carbon merupakan unsur dasar dan penting dalam sebuah alloy baja. Karbon merupakan

paduan utama dan pengaruhnya sangat besar pada baja dengan membentuk karbida Fe3C /

sementit yang keras. Karbon merupakan unsur 'pengeras utama' pada baja. Jika kadar Carbon

ditingkatkan maka akan meningkatkan kekuatannya akan tetapi nilai impactbaja tersebut akan

menurun. Penambahan karbon akan meningkatkan kekerasan dam kekuatan baja. Tetapi sifat

elastisitas, kemampuan untuk di tempa, di las dan di mesin akan menurun. Kandungan karbon di

dalam baja sekitar 0,1 ± 1,7 %, sedangkan unsur lainya dibatasi presentasinya sesuai dengan

kegunaan baja.

11. A typical steel for tubing is AISI 1040, and one for music wire is 1085. Considering their

application explain the reason for the difference in carbon content!

AISI 1040 dan AISI 1085 memiliki kandungan karbon yang berbeda dan yang sangat mencolok

adalah AISI 1085 terdapat tambahan karbon yang lebih banyak didalamnnya sehingga disebut

carbon steel. Terlihat dari tabel bahwa kekuatan kedua material ini sama tetapi dengan

banyaknya kandungan karbon didalam AISI 1085 membuat material ini menjadi lebih lentur

sehingga sering digunakkan untuk wire.

The Effect of Heat Treatment and Aging Process on Microstructure

and Mechanical Properties of A356 Aluminium Alloy Sections in

Casting

K.T. Akhil, SanjiviArul, R.Sellamuthu

Aluminium A356 sangat banyak digunakan pada industri automotive dan aircraft. Material ini mempunyai mechanical properties yang sangat baik, seperti tahan terhadap korosi, kuat dan ringan. Oleh karena itu pengembangan terhadap metrial ini sangat penting mengingat perlakuan panas terhadap logam dapat meningkatkan mechanical properties dari bahan itu sendiri. Mechanical properties juga dapat ditingkatkan dengan cara grain refinement karena mechanical properties suatu material sangat bergantung pada microstructure nya.

Refiniment dapat dicapai dengan menggunakan kekuatan ulltrasound, electromagnetic stirring, dan accumulative roll bonding. Campuran aluminium A356 tuang dibuat dari α-Aldendrites kasar dan acicular-shaped eutectic silicon yang menpunyai mechanical properties yang relatif rendah dan jarang digunakan dalam dunia industri. Perlakuan panas sangat penting untuk memadukan α-Al dendrites kedalam aluminium sehingga didapatkan mechanical properties yang lebih baik.

Setelah dilakukan percobaan didapatkan bahwa perlakuan panas dapat merubah microstructure aluminium A356.

Microstructure dari suatu material juga akan berubah apabila cooling rate direduksi

Jadi, dapat disimpulkan bahwa mechanical properties pada aluminium A356 dapat ditingkatkan melalui perlakuan panas terhadap bahan tersebut. Seperti hasil yang didapatkan dari percobaan dimana kekuatan A356 bertambah dari semulanya 48.31 KJ/m2 menjadi 67.42 KJ/m2, Tensile Stress meningkat dari 60.1 MPa menjadi 145.4 Mpa, Hardness dari 70.4 HV menjadi 82.6 HV. Pengurangan section size juga berpengaruh dalam proses grain refinement, dimana semakin kecil section size maka mechanical properties juga akan semakin baik. Namun, section size tidak berpengaruh pada proses heat treatment.