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Effects Of High Content Of Co On Properties And Glass-forming Ability Of Fe-based Bulk Amorphous Alloy

Posted on:2014-01-31Degree:MasterType:Thesis
Country:ChinaCandidate:J L LiuFull Text:PDF
GTID:2251330422953279Subject:Materials science
Abstract/Summary:PDF Full Text Request
In this thesis, Fe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8) samples were prepareby a non-consumable arc melting. The constructure and pricipitated phases ofFe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8) bulk amorphous alloy were determinedby X-ray diffraction(XRD) and high-resolution transmission electronmicroscopy(HRTEM), respectively. The thermodynamic parameters and glass-formingability of Fe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8)bulk amorphous alloy wereanalyzed and researched with differential scanning calorimeter(DSC). The thermalconductivity meter of laser flash method was applied to test the thermal conductivity ofFe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8) bulk amorphous alloy. Kelvin scanningprobe was used to measure the surface electrical potential energy ofFe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8) bulk amorphous alloy. At the same time,depending on the eletrochemical workstation to research the effects of the change of Cocontents on the corrosion resistance of Fe-based bulk amorphous alloy in3.5%NaClsolution. Finally, the mechanical performance of Fe-based bulk amorphous alloy wasperformed using indentation test method.The research results reveal that high Co contents have significantly influence in theglass-forming ability of Fe-based bulk amorphous alloy, when the contents of Coreached20%, the Fe-based bulk amorphous alloy have the best GFA, it has a relativelyhigh glass transition temperature which is810.5K, as well as has the highest value ofsupercooled liquid region,△Txis98.5K,which implys the bulk amorphous alloy haveexcellent thermal stability. Then the results of theraml conductivity of Fe-based bulkamorphous alloy display that with the increase of Co content, the thermal conductivityof Fe-based bulk amorphous alloy decreased firstly then increased. When the content ofCo is20%, the thermal conductivity is just7.11W/m-1.k-1, the higher the temperature,the higher the thermal conductivity of Fe-based bulk amorphous alloy. The hardness ofFe-base bulk amorphous alloy can be improved by the addition of Co content, however,its fracture toughness will be damaged. The fracture toughness can be enhancedobviously through different heat treatment parameters. The main crystallization phasesof heat treatment Fe-based bulk amorphous alloys are Cr23C6、Fe23B6、Fe3B、α-Fe、(FeCr)23B6,et al. Ultimately, as-cast Fe24+XCo24-XCr15Mo14C15B6Y2(x=0,2,4,6,8)bulk amorphous alloy displayed excellent corrosion resistance in3.5%NaCl solution, whenthe content of Co is22%, which have the highest self-corrosion potential which is-0.084, its resistance is up to3.848×106Ω·cm2. The study of corrosion resistance on thealloy which have the strongest glass-forming ability and its components after heattreatment implys that it has the best corrosion-resistance in3.5%NaCl solution when itis in the totally amorphous state, in that state its relative surface electrical work functioncan be up to-240meV. with the increase of the temperature of the heat treatment, thecorrosion-resistance property is lower, to some extent, it exists some relationshipbetween surface electrical work function and the corrosion-resistance, it can begeneralized that the higher the surface electrical work function, the better thecorrosion-resistance.
Keywords/Search Tags:bulk amorphous alloy, glass-forming ability, thermal conductivity, mechanical property, corrosion-resistance
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