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Formation and Properties of the Novel Pr-based Bulk Metallic Glasses

Author: ZhaoZuoFeng
Tutor: WangWanLu
School: Chongqing University
Course: Condensed Matter Physics
Keywords: Bulk metallic glass Crystallization Kinetics Fragility parameter m Glass transition Relaxation
CLC: TG139.8
Type: Master's thesis
Year: 2004
Downloads: 86
Quote: 1
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Abstract


In this thesis, a new type of Pr-Cu-Ni-Al-based bulk metallic glass as the research object, this system amorphous formation range, forming ability and thermal properties were studied and analyzed. Then select one of the glass-forming ability of the best Pr60Cu20Ni10Al10 samples, ultrasound, crystallization kinetics, the nature of supercooled liquid, glass transition and relaxation behavior. Copper mold suction casting method amorphous samples obtained Pr60Cu20Ni10Al10 maximum diameter of 5 mm, this new Pr-based bulk metallic glass has a distinct glass transition and stable supercooled liquid region, and its glass transition temperature is very low, at a heating rate of 10 K / min when 409 K, and this sample at room temperature to render the paramagnetic. In this composition range studied, as the Al content (at%) of the increase, Pr-Cu-Ni-Al-based amorphous metallic glass formation range to the region of low movement Pr content, and the content of Cu and Ni stepped down is rendered. When the Al content is too low (≤ 10) or too high (≥ 40), the system will become amorphous formation range is very small, can not even form a completely amorphous. For this system, the glass-forming ability of several commonly used criterion such as γ, the supercooled liquid region width ΔT about glass transition temperature Trg conclusions and experimental results obtained are inconsistent. Illustrate this criterion can not be accurately predicted several Pr-(Cu-Ni)-Al-based metallic glass glass-forming ability of the metallic glass formation mechanism remains to be studied in depth. Ultrasound results showed that: with several other typical bulk metallic glass compared, Pr60Cu20Ni10Al10 bulk metallic glass Young's modulus, shear modulus and bulk modulus is significantly lower, while the Poisson's ratio with several other close metals glass, indicating that inhibition of Pr60Cu20Ni10Al10 bulk metallic glass and the long-range atomic rearrangement ability to move several other typical metal and glass is relatively close. Some typical metal with glass of comparison, the method of Kissinger glass transition and crystallization activation energy Eg, Ep somewhat lower, show that the metallic glass supercooled liquid more easily obtain enough energy to carry out long range diffusion. Pr60Cu20Ni10Al10 brittleness parameters (m = 31) than that of typical metal closer to the glass-glass boundary, which in the metallic glass in the supercooled liquid is rare. Using the free volume theory qualitatively explains the experimental thermal analysis of the glass transition phenomenon occurs, and with this theory to explain the observed in experiments protrusion (Overshoot) phenomenon.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy > Amorphous alloy
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