Sains Malaysiana 36(2): 195-200 (2007)

Nitridation of Al-Mg-Si Alloys Through Dynamic Heating

(Penitridaan Aloi Al-Mg-Si Secara Pemanasan Dinamik)

Roslinda Shamsudin, Abdul Razak Daud & Muhammad Azmi Abdul Hamid

School of Applied Physics, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, D.E.,

Malaysia

Saiful Rizam Shamsudin

School of Materials Engineering

Kolej Universiti Kejuruteraan Utara Malaysia

02600 Arau, Perlis

Received : 19 December 2006 / Accepted: 26 Mac 2007

ABSTRACT

Nitridation behaviour of Al-Mg-Si alloys was studied as a function of temperature by means of thermogravimetry method. A reactive gas, N₂-4%H₂ at a rate of 10 ml/min was purged into the thermogravimetry analyser chamber. The Al alloys were heated from 25^oC to 625^oC at the heating rate of 15^oC/min and then reduced to 3^oC/min until it reached 1500^oC. It was found that by varying the amount of Mg and Si in Al-Mg-Si alloys significantly influenced the growth of the composites. A differential thermogravimetric curve shows the Mg containing alloys experienced many steps of chemical reactions.  This indicates that besides AlN presence as a major phase, other compounds also exist in the final product. The X-ray diffraction results confirmed the existence of oxide phases such as a-Al₂O₃, MgAl₂O₄ and MgO in addition to residual Si and Al metal. The presence of oxide compounds is believed to be due to the reaction between the alloying elements and residual oxygen gas left in the reaction atmosphere. It was also found that Si could play a role in promoting the weight gain of the composite produced.  The heating rate has also a profound effect on the weight gain, whereby higher heating rate resulted in low yielded of AlN during the nitridation reaction of the Al-Mg-Si alloys. 

Keywords:  Thermogravitmetry;  nitridation; dynamic heating; AlN

ABSTRAK

Kelakuan penitridaan aloi Al-Mg-Si dikaji sebagai fungsi suhu menggunakan kaedah termogravimetri.  Gas reaktif N₂-4%H dimasukkan ke dalam kebuk analisis termogravimetri pada kadar 10 ml/min. Aloi Al dipanaskan daripada suhu 25°C hingga 625°C pada kadar 15°C/min dan kadar tersebut kemudian dikurangkan kepada 3°C/min sehingga suhu mencapai 1500°C.  Didapati dengan mempelbagaikan amaun Mg dan Si dalam aloi Al-Mg-Si, mempengaruhi pertumbuhan komposit dengan signifikan. Lengkung perbedaan termogravimetri mempamirkan aloi yang mengandungi Mg mengalami langkah tindakbalas kimia yang banyak.  Ini menunjukkan selain AlN wujud sebagai fasa dominan, komponen lain turut hadir dalam produk akhir.  Keputusan pembelauan sinar-X mengesahkan kehadiran fasa oksida seperti a-Al₂O₃, MgAl₂O₄ dan MgO sebagai tambahan kepada logam Al dan Si.  Kehadiran sebatian oksida dipercayai disebabkan oleh tindakbalas antara unsur pengaloian dan gas oksigen tersisa yang masih tinggal dalam atmosfera tindakbalas.  Si juga didapati memainkan peranan dalam mempromosi pertambahan berat komposit yang dihasilkan.  Kadar pemanasan juga mempengaruhi pertambahan berat dimana kadar pemansan yang tinggi mengakibatkan penghasilan AlN yang rendah semasa tindakbalas penitridaan aloi Al-Mg-Si. 

Kata kunci: Termogravimetri; penitridaan; pemanasan secara dinamik; AlN

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