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Morphological Evolution during Partial Re-Melting of AISI D2
Cold-Work Tool Steel
(Perubahan Morfologi Keluli Kerja Sejuk AISI D2 melalui
Peleburan-Semula-Separa)
M.N. MOHAMMED, M.Z. OMAR*, J. SYARIF & M.S. SALLEH
Department of Mechanical and Materials
Engineering, Faculty of Engineering and Built Environment
Universiti Kebangsaan Malaysia, 43600
Bangi, Selangor, Malaysia
Diserahkan: 28 Disember 2012/Diterima: 26 November 2013
ABSTRACT
The impact of isothermal temperature and holding time on the microstructural
evolution process is studied. This process is used to produce globular
microstructures during partial re-melting of AISI D2 cold work tool steel.
The experimental results showed that the optimum process factors
should be selected according to the criteria for average grain size
and shape factor and also by acknowledging the distribution of the
liquid phase around the grains. With increasing isothermal temperature
and holding time, the liquid phase starts to diffuse into the grain
boundaries and spread more evenly. Also, the equiaxed grains were
transformed into near-globular shape, which makes the grain size
and shape factor more favourable for thixoforming. The work shows
that the optimal process condition for the thixoforming of AISI D2 is 1340°C and
5-min holding time, having a shape factor of 1.13 and a particle
size of 51 μm.
Keywords: AISI D2; direct partial re-melting;
microstructure evolution; thixoforming
ABSTRAK
Kesan suhu dan masa memegang proses evolusi mikrostruktur telah
dikaji. Proses ini digunakan untuk menghasilkan mikrostruktur globular untuk
besi gred AISI
D2. Keputusan uji kaji menunjukkan bahawa proses optimum dipilih
mengikut kriteria untuk saiz ira purata dan faktor bentuk dan juga menggunakan
pengagihan fasa cecair sekitar ira yang terbentuk. Dengan
peningkatan suhu dan masa, fasa cecair mula meresap ke dalam sempadan ira dan
tersebar lebih merata. Ira juga telah berubah ke dalam
bentuk bulat, yang menjadikan saiz ira dan faktor bentuk yang lebih baik untuk
kerja pembentukan-tikso. Kerja-kerja ini menunjukkan bahawa keadaan
proses yang optimum untuk pembentukan-tikso D2 AISI ialah 1340°C dan
masa yang diambil ialah 5 min. Ia mempunyai faktor bentuk 1.13 dan saiz zarah
51 μm.
Kata kunci: AISI
D2; evolusi mikrostruktur; mengarahkan sebahagian
lebur semula; pembentukan-tikso RUJUKAN
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*Pengarang untuk surat-menyurat; email: zaidi@eng.ukm.edu.my
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