| Zirconium alloys have been widely used in the nuclear reactor clad material for its small neutron absorption cross-section,good mechanical properties,corrosion and radiation resistance.Improving the properties of zirconium alloys,including mechanical properties,creep properties and corrosion resistance,was demanded by the nuclear industrial for the requirement of high burning up.Sn,Mo,Nb and Fe are important additional elements of zirconium alloy materials.In recent years,the addition of Mo and Fe elements has drawn more attentions.Mo and Fe can improve the mechanical properties,creep resistance and corrosion resistance of zirconium alloy.The study of the phase diagram and the properties of the Zr-Sn-Mo-Nb-Fe alloy system is beneficial to the development and application of new zirconium alloys.In this paper,by using the universal tensile testing machine,hardness tester,nano indentation tester and transmission electron microscopy(TEM)to study the mechanical properties,creep and corrosion resistance of Zr-1.0Sn-xMo-1.ONb-0.1Fe(x = 0.2,0.4,0.6,0.8)and Zr-1.0Sn-0.5Mo-1.0Nb-yFe(y = 0.1,0.3,0.5,0.8)zirconium alloys.By using X ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and other experimental methods to study the(Zr-2.0Sn)-Nb-Fe pseudo three element system of 700? isothermal section in(Zr-2.0Sn)rich area,the following results are obtained:(1)The mechanical properties of Zr-1.0Sn-xMo-1.0Nb-0.1Fe(x = 0.2,0.4,0.6,0.8,wt.%)alloys were studied with the variation of Mo content.The yield strength and tensile strength of zirconium alloy reach maximum of 722.1 MPa and 867.3 MPa respectively,for the alloy containing 0.4 wt.%Mo,and the plasticity is 33.0%,which less than Mo content is 0.8 wt.%alloy.With the increase of Mo content,hardness of zirconium alloys is increasing on the whole.While,young's modulus decreases and it increases as the maximum contact stress increases.The creep resistance of zirconium alloy increases with the increase of Mo content.The maximum value is for the content of Mo is 0.8 wt.%.When the maximum stress is 40 mN,the creep stress index reached 3.8,which is higher than that of pure zirconium.The creep stress exponent and creep stress index also increase with the increase of the maximum contact stress,however,the variation trend of creep properties is unchanged.As for the corrosion resistance,the addition of Mo improves the corrosion resistance of zirconium alloy to a certain extent.The corrosion rate measured by weight loss method of the alloy 1,which Mo content is 0.2 wt.%,is only 0.002 mg cm'2.h-1,the electrochemical tests show that the corrosion current density of this alloy is 4.68×10-5 mA·cm-2,and the impedance is 2118.36 ?cm2.Three groups of experiments show that the best corrosion resistance of zirconium alloy is the 0.2 wt.%Mo.(2)The mechanical properties of Zr-1.0Sn-0.5Mo-1.0Nb-yFe(y = 0.1,0.3,0.5,0.8,wt.%)alloys were studied with the change of Fe content.In the conventional mechanical properties,when the Fe content is 0.5 wt.%,the yield strength,tensile strength and plasticity were 681.1 MPa,814.6 MPa and 30.2%,respectively.With the increase of Fe content,the hardness increases,the Young's modulus shows a decline trend,the hardness and modulus increase as the increase of maximum contact stress.The creep resistance of zirconium alloy increases and then decreases with the increase of Fe content.The best one is the alloy with content of 0.1 wt.%Fe,Whose creep stress exponent reaches the maximum of 3.5 when the stress is 40 mN,this value is less than that of pure zirconium and other zirconium alloy.As for the corrosion resistance,the addition of Fe improves the corrosion resistance of zirconium alloy to a certain extent.For the 0.1 wt.%Fe,the corrosion rate of weight loss obtained is 0.033 mg·.cm-2h-1.The electrochemical tests show that the corrosion current density is 1.84×10-5 mA.cm-2,and the resistance is 1636.84 ?cm2.The results show that the 0.1 wt.%Fe is the highest corrosion resistance.With the increase of Fe content,the corrosion resistance decreases.(3)The(Zr-2.0Sn)-Nb-Fe pseudo ternary system was studied to determine the isothermal section at 700?.The(Zr-2.0Sn)-Nb-Fe pseudo ternary system is composed of one single phase region,two two-phase regions,three phase regions and three four-phase zones in the(Zr-2.0Sn)rich region of the phase diagram.The study found that the presence of three four-phases,which are(a-Zr)+(?-Zr)+(ZrNb)2Fe + ?,Zr2Fe + Zr(NbFe)2 +(ZrNb)2Fe + ? and Zr(NbFe)2 +(p-Zr)+(?-Nb)+ ?. |
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