改良劑(鍶/鑭)與熱處理對亞共晶Al-Si合金微結構及導熱性質之影響;Effects of modifiers (Sr/La) and heat treatments on the microstructures and thermal conductivity of hypoeutectic Al-Si alloys

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Title:	改良劑(鍶/鑭)與熱處理對亞共晶Al-Si合金微結構及導熱性質之影響;Effects of modifiers (Sr/La) and heat treatments on the microstructures and thermal conductivity of hypoeutectic Al-Si alloys
Authors:	潘則銨;Pan, Tse-An
Contributors:	材料科學與工程研究所
Keywords:	鋁矽合金;改良劑;鍶;鑭;球化熱處理;鑄造流動性;熱傳導性;導電性;背向電子散射繞射;Al-Si alloy;Sr;La;spheroidization annealing;fluidity;thermal conductivity;electrical conductivity;electron back scatter diffraction
Date:	2023-07-28
Issue Date:	2024-09-19 15:50:22 (UTC+8)
Publisher:	國立中央大學
Abstract:	隨著5G產品的發展，高頻電子元件所散出的熱量愈來愈高，如何提高散熱片的材料熱傳導率為一重要課題。本研究旨在滿足對高熱傳導性和優異鑄造性的散熱材料的需求。本研究透過不同改良劑(鍶/鑭)添加至亞共晶鋁矽合金中，並進行不同時間的球化退火，以改良共晶矽形貌進而改善合金導熱性。研究結果顯示，對於鑄造態合金而言，添加鍶可以透過增加共矽內雙晶濃度，將板狀的共晶矽完全轉變為絨毛狀結構，減少對電子及聲子的阻擋，能顯著提升導熱性和導電性。添加鑭也可以將共晶矽改變為絨毛狀結構，但是效果較添加鍶差。合金的流動性隨著矽含量的增加而提升，且硬度與矽含量也呈正相關，添加鍶和鑭則幾乎對流動性及硬度沒有影響。在球化退火合金中，無論是改良合金還是未改良合金都會經歷共晶矽的破碎和球化，從而提高導熱性及導電性。在經過4小時的球化退火後，由於導電性與導熱性對不同缺陷敏感度的不同Al-2Si和Al-4Si中導電性與導熱性出現相反的趨勢。此外，共晶Si的破碎和球化會導至鋁基地中的缺陷增加，使導熱性與導電性下降。這些發現對於開發高性能散熱材料提供了新的解決方案。其望能促進散熱材料的發展，為高功率應用領域提供更可靠和高效的解決方案。;The increasing power density involved in various applications presents significant challenges for heat dissipation. Materials with high thermal conductivity are vital to address these limitations and enable the development of high-performance solutions. This study aims to address the need for heat-sink materials with high castability and excellent thermal conductivity. Hypoeutectic Al-Si alloys are modified with different additives, including Sr and La, and subjected to spheroid annealing of varying durations to comprehensively investigate the effects of modifiers and heat treatments on the microstructures and thermal conductivity of these alloys. The findings reveal that, in the as-cast alloys, the addition of Sr completely transforms the plate-like eutectic Si into a fibrous-like structure, significantly improving electrical and thermal conductivity. Adding La also modifies the eutectic Si into a fibrous-like structure, albeit with a lesser improvement in conductivity. Additionally, the fluidity of the alloys improves with higher Si content, while the hardness exhibits a positive relationship with Si content and these are minimally affected by addition of Sr and La. In spheroid-annealed alloys, both modified and unmodified alloys undergo the fragmentation and spheroidization of eutectic Si, leading to improved electrical and thermal conductivity. The sensitivity of point defects and structural defects causes opposing trends in electrical and thermal conductivity between Al-2Si and Al-4Si after 4 hr of spheroid annealing. Furthermore, the fragmentation and spheroidization of eutectic Si involve defects in the Al matrix, resulting in decreased electrical and thermal conductivity, particularly for alloys with coarse eutectic Si in the as-cast state.
Appears in Collections:	[Institute of Materials Science and Engineering] Electronic Thesis & Dissertation

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