液相分離Zr-Ti-Cu-Nd金屬玻璃複合材料之微結構及機械性質探討

Abstract

在這個實驗中以Zr-Ti-Cu-Nd 金屬玻璃複合材料為研究對象。首先利用熔體紡絲的方式製作成金屬玻璃薄帶。透過一系列的研究來觀察其為結構和機械性質的關係。Zr-Ti-Cu-Nd金屬玻璃複合材料主要是利用部分元素液相不互溶的特性來形成二相混合的複合材料。在這個實驗中，透過觀察微結構以及元素分布的情況，相分離的現象將會進一步地被討論。由於混合熱的影響，Nd從Zr/Ti所形成的基材分開，而Cu的分布也因為受到元素間混合熱差異的影響變得不均勻。同時經由掃描式電子顯微鏡的觀測可以發現在整個薄帶中，析出物的分佈以及大小並非均勻散布。而主要的成因則是因為薄帶內外降溫速率不同所導致。在硬度測試中，硬度的分布也會受到為結構的影響，導致薄帶中央較表面來得軟。模量映射的結果則顯示基材具有較高的儲存模數而析出物則是有較高的損失模數。透過微觀的壓縮試驗能發現當Nd的含量越多時，複合材料的塑性也會被提升的更多，這樣的結果說明了在金屬玻璃內析出第二相能夠有效的提升其延展性。

The Zr-Ti-Cu-Nd metallic glass ribbons with different amounts of Nd were fabricated by melt spinning. The ribbons were used to examine the microstructure and the mechanical properties. Since the positive mixing enthalpy between some elements, the phenomenon of liquid phase separation occurred and formed the metallic glass composites. Specifically, Nd separated from the Zr/Ti based metallic glass matrix and precipitated with Cu during the cooling process. In addition to Nd, the distribution of Cu was nonuniform because its mixing enthalpies with Nd and Zr/Ti were different. This was verified by energy-dispersive X-ray spectroscopy. The images from scanning electron microscopy showed that the microstructure was inhomogeneous across the thickness of the ribbon because of the different cooling rates. By examining the hardness, the ribbons were softer in the middle and harder on both surface sides because of the different distributions of precipitates. Using modulus mapping, the matrix showed the higher storage modulus and the precipitates showed the higher loss modulus in contract. The micropillar compression tests showed that the samples with more additive Nd contents presented larger plasticity which proved that the soft second phase in these composites was effective in plasticity enhancements.