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URN etd-0819115-234434 Statistics This thesis had been viewed 921 times. Download 1 times. Author Cheng-Kang Chen Author's Email Address No Public. Department Materials Engineering Year 2014 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 141 Title High Strength High Ductility Die Casting Al Alloy with Low Iron Content Keyword low-iron ADC3 Al alloy high strength high ductility high strength high ductility ADC3 Al alloy low-iron Abstract An investigation on the development of high strength high ductility die casting Al alloys with low-none iron content, based on a ADC3 Al alloy (Al-9.5Si-0.8Fe-0.4Mg), was carried out in this study. The first part of this study was to examine the microstructures and the mechanical properties of a series of ADC3-base alloys with different iron content and modified alloy compositions. The second part of this study utilized a T5 and a spheroidization heat treatments to further improve the mechanical properties of the modified ADC3-base alloys.
The results show that, when iron content in gravity cast ADC3-base alloys was reduced from 0.8% to 0.4%, the amount of plate-like iron-rich compound with sharp edges was found decreased significantly. As such, the ductility of the low-iron ADC3-base alloys increase accordingly. Among the low-iron ADC3-base alloys studied the ADC3S2 alloy containing Cr and Zr (Al-9.5Si-0.4Fe-0.4Mg-0.3Cr-0.3Zr-0.02Sr) exhibited the best combination of high mechanical strength and high ductility. While in the iron-free ADC3-base alloys studied the non-
heat–treatable ADC3S7 alloy (Al-9.5Si-0Fe-0Mg-0.6Mn-0.3Cr-0.3Zr-
0.02Sr) exhibited the best combination of high mechanical strength and high ductility. In comparisons of mechanical properties in the as-cast condition of die casting ADC3 (0.8 Fe), ADC3S2 (0.4 Fe) and ADC3S7 (Fe-free) alloys, the mechanical properties of low-iron ADC3S2 and iron-free ADC3S7 Al alloys are very similar and better than that of ADC3 (0.8 Fe). The YS, UTS and ductility values of as-cast ADC3S2 and ADC3S7 alloys are in the range of 190~192 MPa, 296~298 MPa and 8.1~8.2%, respectively. When subjected to a T5 treatment at 175oC for 8 h, the die cast ADC3S2 exhibited far better mechanical properties than the other two alloys, with YS, UTS and ductility of 260 MPa, 339 MPa and 7.8%, respectively. However, when subjected to the spheroidization treatment at 350oC for 0.5 h, the mechanical properties of three die cast alloys are very alike. The YS, UTS and ductility values in the die casting ADC3 (0.8 Fe), ADC3S2 (0.4 Fe) and ADC3S7 (Fe-free) alloys are in the range of 146~158 MPa, 224~245 MPa and 12.3%~15.0%, respectively.
Advisor Committee Chih-Fu Yang - advisor
Files Date of Defense 2015-07-23 Date of Submission 2015-08-20