以熱處理改良擠壓鑄造之A356鋁合金及A356/SiC複合材料之導熱性質

The Effect of Heat Treatment on the Thermal Conductivity of Squeeze Casting A356 Al Alloy and A356/SiC Composite

李其鴻(C.H. Lee) ； 鍾佑祥(Y.X. Zhong) ； 楊智富(C.F. Yang) ； 林永仁(Y.J. Lin) ； 張鈞富(Oliver Chang)

《鑄造工程學刊》 45卷3期 (2019/09) Pp. 1-12

摘要

本研究旨在探討以熱處理來改良A356鋁合金及Al/SiC複合材料之熱傳導率，使用材料包括擠壓鑄造之A356鋁合金，以及以擠壓鑄造法將A356鋁溶湯滲入80%體積分率之SiC胚體所製成之Al/SiC複合材料。採用之熱處理溫度範圍為200℃~600℃，時間為半小時。熱處理後之材料使用OM進行微觀結構分析，並以XRD分析試片之晶格常數變化，以及分析熱處理對材料密度、導電率及熱傳導率之影響。實驗結果顯示，580℃/0.5 h熱處理能顯著提升A356鋁合金鑄件之密度，350℃/0.5 h之熱處理則能有效的析出A356鋁合金Pri-α基地相所固溶之合金元素，提升壓鑄A356鋁合金之熱傳導率。若使用580℃/0.5 h + 350℃/0.5 h二段式熱處理，則能將A356鋁合金鑄件之熱傳導率由127.2 W/（m∙K）提升至155.3 W/（m∙K），此二段式熱處理與單純施行350℃/0.5 h（一段式）熱處理者提升熱傳導率之效果相近。對Al/SiC複合材料而言，由於採用持溫持壓之擠壓鑄造法，鑄態複材內A356鋁合金與SiC胚體充分密合，經量測其密度為3.08 g/cm^3，接近100%理論填充密度，而熱傳導率則高達197.7W/（m∙K）。複材經二階段式熱處理後，其密度及熱傳導率皆未有可察覺之提升效果。此乃因本研究製備之Al/SiC複材已接近100%理論填充密度，故580℃/0.5h之「提升密度熱處理」對Al/SiC複材密度提升效果不大。此外，由於A356鋁合金在複材中所佔比例不高（僅20%），所以350℃/0.5h之「析出熱處理」，雖能提升複材中金屬之熱傳導率，但對總體複材之熱傳導率並未有可察覺之提升效果。

關鍵字

熱處理 ； A356鋁合金 ； Al/SiC複合材 ； 熱傳導率

並列摘要

The purpose of this study is to investigate the improvement of thermal conductivity in A356 Al alloy and Al/SiC composites by using heat treatment. The materials used include a squeeze casting A356 Al alloy and an Al/SiC composite made by high pressure infiltration of A356 Al melt into 80 vol% SiC perform in a squeeze casting machine. The heat treatment was carried out at temperatures ranging from 200 to 600°C for a fixed time period of 30 min. After heat treatment, the microstructures and the lattice constant of A356 Al alloy were analyzed by OM and XRD, respectively. And the effects of heat treatment on density, electrical conductivity and thermal conductivity of A356 Al alloy and Al/SiC composite were evaluated. The results show that, among the various heat treatment conditions studied, the 580°C/0.5h heat treatment significantly increased the density of as cast A356 Al alloy. While the 350°C/0.5 h heat treatment effectively depleted the solutes content in the Pri-α matrix of A356 Al alloy, which results in a remarkable increase of thermal conductivity. By using a 2-step heat treatment of 580°C/0.5 h + 350°C /0.5 h, the thermal conductivity of as cast A356 Al alloy was found increased from 127.2 W/(m∙K) to 155.3 W/(m∙K). But for the Al/SiC composite, it was found that the 2-step heat treatment has little effect on both density and thermal conductivity of the Al/SiC composite.

並列關鍵字

heat treatment ； A356 Al alloy ； Al/SiC composites ； thermal conductivity