離心加壓力及熔液處理對於A390過共晶鋁矽合金之顯微組織及耐磨耗性之影響

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

賴易辰(Y. C. Lai) ； 鄭百倫(B. L. Zheng) ； 潘永寧(Y. N. Pan)

《鑄造工程學刊》 43卷2期 (2017/06) Pp. 25-38

摘要

A390過共晶鋁矽合金在重力鑄造時，由於矽的比重(2.33 g/cm^3)較鋁(2.74 g/cm^3)低，因此在凝固過程中容易產生初晶矽(primary silicon)上浮的現象，而使得同一鑄件在不同位置 的機械性質不一致。本研究利用矽與鋁比重之差異，以一自行設計之旋轉裝置進行A390鑄造，使得A390之凝固過程在旋轉狀態下受到一穩定離心力作用，促使比重較低、硬度較高的初晶矽會發生徑向偏析，往旋轉軸中心側聚集，預期鑄件在該局部位置能得到較高比例的初晶矽分佈，進而達到提升耐磨耗性之效果。本研究在固定轉速150 rpm(重力倍數約10 G)之離心鑄造條件下，探討P之細化處理(針對初晶矽)、Sr之調質處理(針對共晶矽)以及P+Cr複合細化處理(針對初晶矽)等三種不同熔液處理對於A390過共晶鋁矽合金之顯微組織及耐磨耗性之影響，最後利用迴歸分析以獲致各參數與耐磨耗性之關係。

關鍵字

A390 ； 離心加壓力 ； 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 portion 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 Si gravity segregation, and further to enhance this segregation nature by employing centrifuging casting process to achieve better wear resistance in specific area of the castings. A centrifuging casting apparatus was constructed which allows the castings to be solidified under the centrifugal force. Under the centrifuging casting condition, the primary Si particles which have low specific gravity and high hardness tend to move toward the rotational axis and aggregate at the inner portion of the castings, and thus to enhance the wear resistance of the A390 alloy. In addition, P refinement (for primary Si), Sr modification (for eutectic Si) and P + Cr refinement (for primary Si) of A390 alloy were performed to examine the effects of these different melt treatments on the microstructure and wear resistance property of the centrifuging castings at a rotational speed of 150 rpm (~10G). Further, the relationship between the microstructure features obtained and the wear resistance property was evaluated by using regression analysis.

並列關鍵字

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