| Summary: | 碩士 === 逢甲大學 === 材料科學學系 === 88 === Amorphous is random state in microstructure, which has some special properties relative crystalline material in engineer apply, such as magnetic, corrosion resistance and mechanical strength. In traditionally, making metal amorphous was by ultra-high cooling rate from high temperature metal vapor or liquid to avoid crystalline when solid reaction happened. Mechanical alloying is a kind of solid state amorphous reaction . The main general idea of mechanical alloying is collision of powder and mill ball. By mill time goes by, the pure metal powders show several process like cold welding, break, rewelding and amorphization. With add of milling time, amorphization will be more complete in some concentration by the diffusion which assist by defect that form by the cold welding, fracturing and rewelding previously and the temperature assist by collision.In this experience, we use Fe and Nb powders, weight corresponding to their chemical compositions, FexNb100-x with X=10, 20, 30, 40, 50, 60, 70, 80 and 90, we use SPEX8000D which of 1725 rpm, in Ar atmosphere, the ball-to-powder ratio is 5:1, getting powders at the setting time, SEM was empleyed to observe particle cross-section and appearance, XRD will show us the crystalline state of the powders, hardness test will help us to know the relation of milling time with micro-structure hardness, thermal analysis is going to tell us the Tx of the powders.We get good result that is mechanical alloying is a useful method for solid state amorphization reaction. In terminal compostion, we get Fe solid solution by Fe90Nb10 after 15 hours MA, and get its(Fe) lattice constant from 0.287nm become 0.290nm. and its nearest distance is 0.2456nm. By the same method, we can find Fe10Nb90 become Nb solid solution after 15 hours milling, and get its(Nb) constant lattice from 0.33nm to 0.3237nm by 10% Fe exist in Nb solid solution. Its average nearest distance will be 0.2747nm. Amorphous FexNb100-x powders were prepared by mechanical alloying pure crystalline iron and niobium powders in the concentration region 30≦x≦70. The process consists of repeated mechanical mixing, cold welding, fracturing, and rewelding of ultrafine alloy powder. By doing so, they can become amorphous alloy or solid solution.We also get microhardness in amorphous Fe50Nb50 is 820±150. Than we use DTA to get Tx of the amorphous alloy powders Fe50Nb50, which was producted by SPEX8000D for 15 hours milling.The Tx of the powders is 798℃.
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