STUDY OF MICROSTRUCTURE STABILITY OF AL0.25COCRCUFENI HIGH ENTROPY ALLOY WITH ISOTHERMAL OXIDATION TREATMENT AT TEMPERATURES OF 800?, 900?, AND 1000?
The Al0.25CoCrCuFeNi alloy is a high-entropy alloy based on transition metals, designed for high-temperature applications due to its good mechanical properties, high melting point, and excellent high-temperature resistance. This alloy is one of the selected materials for space development, specif...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/74866 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | The Al0.25CoCrCuFeNi alloy is a high-entropy alloy based on transition metals,
designed for high-temperature applications due to its good mechanical properties,
high melting point, and excellent high-temperature resistance. This alloy is one of
the selected materials for space development, specifically in the production of
combustion chambers and rocket nozzles in the National Aeronautics and Space
Agency. The elements used in this alloy are relatively cheaper compared to
refractory elements. The development of the alloy continues by varying the
composition of the elements within the alloy. This experiment involves varying the
amount of aluminum in the equiatomic AlCoCrCuFeNi alloy to Al0.25CoCrCuFeNi,
followed by isothermal oxidation treatment at temperatures of 800?, 900?, and
1000?.
A series of isothermal oxidation experiments were conducted to study the stability
of the microstructure and oxidation behavior of the Al0.25CoCrCuFeNi alloy. The
experiment began with the melting of the alloying elements using a single DC
electric arc furnace, followed by homogenization at a temperature of 1100? for 10
hours in an inert environment using a horizontal tube furnace. Then, metal samples
were cut to produce coupons for subsequent isothermal oxidation testing at
temperatures of 800?, 900?, and 1000?, with varying durations of 2 hours, 16
hours, 40 hours, and 168 hours. The as-oxide samples were characterized using
XRD, SEM-EDS, optical microscopy, and micro vickers hardness tester.
Based on the experimental results, the as-homogenized Al0.25CoCrCuFeNi alloy
consists of two constituent phases: the FCC phase in the dendritic region and the
Cu-rich FCC phase in the interdendritic region. The hardness value of the
Al0.25CoCrCuFeNi alloy decreases from 800? to 900?, but increases from 900?
to 1000?. The oxides formed during the oxidation process include Al2O3, Cr2O3,
Fe3O4, CoO, CuO, NiO, and spinel oxides ((Co,Ni,Cu)(Al,Cr,Fe)2O4), with
different formation mechanisms at each temperature. The oxidation kinetics of the
Al0.25CoCrCuFeNi alloy at 800? and 900? follow logarithmic growth with the
respective equations y = 0.7513log(t+1) with R2 = 0.83 and y = 0.4202log(t+1) with
R2 = 0.81. At 1000?, the oxidation follows parabolic growth with the equation
y = 54.826t with R2 = 0.99. |
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