Abstract
The combined processes; rapid solidification, addition of Cu3P compound and heat treatments to improve the mechanical properties of the hypereutectic Al-13Si, Al-20Si and Al-20Si-1.5Fe-0.7Mn alloys (in wt. %) was studied. Optical microscopy and scanning electron microscopy were used to characterize the microstructures. The mechanical properties were evaluated by tensile tests. It was found that the cooling rate (20-50°C/s) used to solidify the alloys plus the addition of Cu3P compound favored the formation of fine primary Si and the transformation of the Al/Si eutectic from acicular to semi-transformed morphology. The spheroidization of the Al/Si eutectic after heat treatment caused an increase in the elongation (%) compared with the as-cast alloys. Al-13Si alloy showed the highest UTS and elongation (%) values, reaching values up to 215 MPa and 9.6%, respectively. On the other hand, the Al-20Si-1.5Fe-0.7Mn alloy showed the lowest UTS (180MPa) and elongation (3.4%) values. The formation of the Fe-intermetallic compounds caused a negative effect on the mechanical properties of the Al-20Si-1.5Fe-0.7Mn alloy.
Highlights
The hypereutectic Al-Si alloys considered as metalmatrix composites reinforced by hard particles show good wear resistance, low thermal expansion coefficient and high elastic modulus
The purpose of the present work is to improve the mechanical properties of the hypereutectic Al-Si alloy using rapid solidification, addition of phosphorous compounds to decrease the size of primary Si, and heat treatments to modify the Al/Si eutectic
The cooling rate (20-50°C/s) used to solidify the alloys favored the formation of fine microstructures and transformation of the Al/Si eutectic from acicular to semi-transformed morphology
Summary
The hypereutectic Al-Si alloys considered as metalmatrix composites reinforced by hard particles show good wear resistance, low thermal expansion coefficient and high elastic modulus These properties are attributed to the uniform distribution, size and volume fraction of hard Si particles and in some cases for additional Fe-intermetallic compounds in the soft aluminum matrix[1]. These kinds of alloys have been used primarily in the automotive industry and for wear resistant applications. The purpose of the present work is to improve the mechanical properties (elongation % and strength) of the hypereutectic Al-Si alloy using rapid solidification, addition of phosphorous compounds to decrease the size of primary Si, and heat treatments to modify the Al/Si eutectic.
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