Processing, microstructure, and mechanical properties of cast In-Situ Al(Mg, Ti)-Al2O3(TiO2) composite |
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Authors: | Abdulhaqq A Hamid S C Jain P K Ghosh Subrata Ray |
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Affiliation: | (1) the Mechanical and Industrial Engineering Department, Indian Institute of Technology, 247 667 Roorkee (Uttranchal), India;(2) the Metallurgical and Materials Engineering Department, Indian Institute of Technology, 247 667 Roorkee (Uttranchal), India |
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Abstract: | In-situ particle-reinforced aluminum alloy-based cast composites have been synthesized by solidification of the slurry obtained by
dispersion of externally added titanium dioxide (TiO2) particles in molten aluminum at different processing temperatures. Alumina particles (Al2O3) form in situ through chemical reaction of TiO2 particles with molten aluminum. Simultaneously, the chemical reaction also releases titanium, which dissolves into molten
aluminum and results in the formation of intermetallic phase Ti(Al1−x
,Fe
x
)3 during solidification. Increasing the processing temperature increases (1) the amount of elongated as well as blocky intermetallic
phase Ti(Al1−x
,Fe
x
)3, (2) the proportion of alumina particles in the reinforcing oxides, and (3) the porosity content in the resulting cast in-situ composite. The difference in particle content and porosity between the top and the bottom of the cast ingot increases with
increasing processing temperature. The hardness of the cast in-situ composite is significantly more than that of the matrix alloy due to the presence of reinforcing particles, but the hardness
is greatly impaired by the presence of porosity at the top of the cast ingot. The percent elongation of the cast in-situ composite decreases with increasing processing temperature possibly due to increasing porosity as well as an increasing amount
of elongated intermetallic phase, which affects the percent elongation of the matrix alloy. The tensile and yield stresses
of the cast in-situ composite decreases with increasing processing temperature again due to increasing porosity, which affects the ultimate tensile
stress more than the yield stress. In the cast in-situ composite containing 3.31 ± 0.77 vol pct of porosity, the Brinell hardness is about 6 times its yield stress. The estimated
yield stress of the cast in-situ composite at zero porosity as given by the linear least-squares fit appears to increase with particle content at a significantly
higher rate than that predicted by the shear-lag model. |
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