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URN etd-0822116-170700 Statistics This thesis had been viewed 455 times. Download 0 times. Author Che-Wei Hsu Author's Email Address No Public. Department Materials Engineering Year 2015 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 207 Title Effect of special heat treatments and compositional modification on mechanical properties of ADC12 Die casting Al alloy Keyword die cast ADC12 Al alloy special heat treatments Al5FeSi eutectic Si elongation elongation eutectic Si Al5FeSi special heat treatments die cast ADC12 Al alloy Abstract Due to its excellent castability the ADC12 die casting Al alloy is widely used for various consumer products. However, its applications as structural components are limited due to its poor mechanical properties, especially ductility and fracture toughness. As such, a study aims to improve its mechanical properties is conducted. A total of seven ADC12-type alloys, including two commercial ADC12 alloys with different Si contents and five modified ADC12 alloys, namely ADC12(10 Si), ADC12(11 Si) and ADC12-1 ~ ADC12-5, along with the effects of some special heat treatments are tested.
The results showed that, among the various modified ADC12-type alloys studied, the ADC12-2 alloy with additions of 0.02% Sr, 0.3% Cr and 0.3% Zr exhibits proper microstructures in the as cast condition with promising mechanical properties. The Sr modifier and Cr neutralizer have modified the shapes of coarse plate-like eutectic Si into fibrous and the thin sheet-like β-Al5FeSi into small particles of α-Al13(Fe,Cr)4Si4, respectively. The Zr addition, on the other hand, showed only a negligible increase in yield strength of the alloy in the as cast condition. After a 400oC/0.5 h spheroidization treatment a substantial improvement in ductility was observed. From the tensile properties data gathered it was found among the ADC12-type alloys studied only the ADC12-2 alloy exhibited mechanical properties (YS: 218 MPa, UTS: 350 MPa, El: 10.3% and QI: 502 MPa) close to those of the well known gravity casting A356-T6 alloy, which is wildly used as load-bearing structure components. Although some of the ADC12-type alloys may achieve excellent mechanical properties like A356-T6 alloy by a special solid solutioning treatment at 460oC for a period of 0.5~2 h, their mechanical properties are unstable and degrade (become brittle) in the following nature or artificial aging. As such, the special solid solutioning in conjunction with a post aging treatment may not be the proper treatment for ADC12 alloy die castings with satisfactory ductility and toughness.
Advisor Committee Chih-Fu Yang - advisor
Chui-Hung Chiu - co-chair
Chun-Mu Chen - co-chair
Yung-Ning Pan - co-chair
Files Date of Defense 2016-07-28 Date of Submission 2016-08-23