離心力對於A390過共晶鋁矽合金之顯微組織及耐磨耗性之影響

Effect of Centrifuging Force on the Microstructure and Wear Resistance Property of A390 Hyper-eutectic Al-Si Alloy

陳擷安(C. A. Chen) ； 賴易辰(Y. C. Lai) ； 潘永寧(Y. N. Pan)

《鑄造工程學刊》 42卷2期 (2016/06) Pp. 19-28

摘要

A390(Al-17Si-4.5Cu-0.5Mg)過共晶鋁矽合金在鑄造時，由於矽的比重(2.33g/cm^3)較鋁(2.74g/cm^3)低，因此在凝固過程中容易產生初晶矽上浮現象，使得同一鑄件在不同位置的顯微組織及機械性質均不同。本研究即利用此初晶矽與鋁在比重上之差異，在凝固過程中對鑄件施以旋轉離心加壓，促使初晶矽的偏析現象更加顯著，而預期所生產之鑄件在局部位置能達到提升耐磨耗性之目的。分析不同轉速(50rpm、100rpm、150rpm與200rpm)下鑄件不同位置(內側、中央、外側)之顯微組織可以得知，初晶矽之偏析程度隨旋轉速度之增加而增高，且當轉速達到150rpm時，偏析程度達到飽和，而不再隨旋轉速度之增加而增高。又，本研究在固定旋轉速度150rpm之離心鑄造條件下，探討P之細化處理(針對初晶矽)以及Sr之調質處理(針對共晶矽)對於鑄件之內側、中央及外側顯微組織的影響，並進一步探討經不同合金處理之A390鑄件在不同位置之耐磨耗特性。

關鍵字

離心力 ； 初晶矽偏析 ； 細化處裡 ； 共晶矽調質處理 ； 耐磨耗性

並列摘要

While casting the A390 hypereutectic alloy, primary Si particles tend to float to the upper part of the casting due to the difference in specific weight between primary Si particles and the aluminum bulk liquid, the so-called gravity segregation. As a result, the microstructures and the mechanical properties in different parts of the casting vary. This research utilized the above-mentioned phenomenon of the primary silicon segregation, and further to enhance this segregation nature by employing centrifuging casting process to achieve better wear resistance in specific areas of the castings. Under the centrifuging casting condition, the primary Si particles tend to move toward the rotational axis and aggregate at the inner portion of the castings. In this study, various rotational speeds (50rpm, 100rpm, 150rpm and 200rpm) were conducted to evaluate the effect of the rotational speed on the microstructure. The experimental results indicate that the degree of primary silicon segregation toward the inner portion of the casting increases with increasing rotational speed, and reaches a plateau at 150 rpm. In addition, P refinement (for primary Si) and Sr modification (for eutectic Si) of A390 alloy were performed to examine the effects of either P refinement or Sr modification on the microstructures of the centrifuging castings at 150 rpm. Furthermore, the relationship between the microstructure features obtained and wear resistance property was evaluated.

並列關鍵字

A390 ； Centrifuging force ； Primary Si segregation ； Refinement ； Eutectic Si modification ； Wear resistance property