鋯基與鈦基金屬玻璃薄膜應用於7075-T6航空用鋁合金疲勞性質改善之研究

Zr-based and Ti-based Metallic Glass Thin Film Coatings for Fatigue-Property Improvement of 7075-T6 Aluminum Alloy

柯俊宏(Jun-hong Ke)

指導教授 ： 鄭憲清

國立中央大學/工學院/材料科學與工程研究所/碩士(2015年)

摘要

本研究探討7075-T6高強度鋁合金基材披覆鋯基（Zr53Cu30Ni9Al8）99.5Si0.5與鈦基(Ti40Zr10Cu36Nb7Co7)金屬玻璃薄膜應用於抗疲勞性質改善之研究。首先，我們探討鋯基金屬玻璃薄膜厚度對於7075-T6鋁合金疲勞之效果，選擇一最佳膜厚再與相同膜厚之鈦基金屬玻璃進行比較，以研究不同系統之金屬玻璃薄膜成分對於其疲勞性質之影響。而實驗結果發現鋯基金屬玻璃薄膜厚度提升其疲勞性質改善會逐漸減退，疲勞限由披覆200 nm之235 MPa至500 nm之205 MPa明顯降低，這是由於表面粗糙度逐漸提升所導致。此外，濺鍍200 nm鋯基與鈦基金屬玻璃薄膜之疲勞限相較於鋁合金基材提升56.7 %與43.3 %，在250 MPa之交變應力下，鋯基與鈦基金屬玻璃薄膜之疲勞壽命則分別為5.4×10^6次與1.6×10^6次，相較於鋁合金基材之2.0×10^5次高出近26.3倍與7.9倍，而披覆200 nm厚之鋯基金屬玻璃薄膜在表面粗糙度與附著性皆優於鈦基金屬玻璃，因此披覆200 nm之鋯基金屬玻璃為7075-T6鋁合金抗疲勞鍍膜之最佳選擇。

關鍵字

金屬玻璃薄膜 ； 四點彎曲 ； 疲勞性質 ； 7075鋁合金

並列摘要

Due to the high specific ratios of strength to weight of 7075 aluminum alloy, it is widely used in light weight sport equipment, automobile bodies, and aircraft frames. However, the 7075 aluminum alloy has poor fatigue property in comparison to steel. In this study, different thicknesses (namely 200, 300, 400, and 500 nm) of Zr-based ((Zr53Cu30Ni9Al8)99.5Si0.5) and 200 nm Ti-based (Ti40Zr10Cu36Nb7Co7) metallic glass thin films (MGTF) were successfully coated on the 7075 aluminum alloy substrates by DC-sputtering method. Then the fatigue properties of these coated and as-polished samples were tested following the standard of ASTM-C1161-02c. The results revealed that the fatigue life and fatigue strength show an opposite trend with increasing the thickness of MGTF due to the changes of surface roughness and residual stress. The sample coated with 200-nm-thick Zr-based MGTF is found to have the best fatigue properties than others thickness-coated samples. Moreover, the fatigue life of 7075-T6 aluminum alloy can be improved about 26.3 and 7.9 times than the bare one at the high stress level of 250 MPa by coating with 200 nm-thick Zr-based and Ti-based MGTF. In parallel, the improvements of Zr-based and Ti-based MGTF-coated samples in fatigue strength were 235 MPa (56.7 %) and 205 MPa (43.3 %) compared with as-polished sample (150 MPa).
Based on the TEM examination, the formation of offsets and cracks from the surface of specimen was revealed to be effectively restricted by both MGTF coatings. This is attributed to the high strength, good flexibility, and strong adhesion of both MGTF coatings, which can provide effective compressive stress to suppress the slip band protruding. In summary, Zr-based MGTF coating is believed to be a promising coating material for improving 7075-T6 aluminum fatigue properties.

並列關鍵字

Metallic Glass Thin Film ； Four-Point-Bending ； Fatigue ； 7075 Aluminum Alloy

參考文獻

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