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NiAl合金具有许多优异的物理性能:它的密度低,仅为5.86g/cm~3;它的熔点高达1640℃;它有高的热传导性,是Ni基高温合金的4～8倍;它还具有良好的抗氧化性能.由于NiAl合金具有这些优点,使得它可望成为新一代高温结构材料但单晶和多晶NiAl合金在室温下很脆,这阻碍了它的现时应用Geoyge等人研究了微量B,C,Be对NiAl合金的断裂和晶界化学的影响,结果表明,用B,C,Be对NiAl合金微合金化,没有达到提高合金塑性的目的.而Rachinger等人的实验结果表明,用Cr,Co,Fe,Mn等元素对NiAl合金化能使NiAl有序能减小.Fe含量较高的Ni-20AI-30Fe经挤压后,其室温塑性延伸率达8%目前还没弄清这些合金元素影响NiAl合金力学性能的微观机制.本文通过测量NiAl,Ni_(48)Al_(45)Fe_7和Ni_(50)A1_(20)Fe_(30)的正电子寿命谱,揭示NiAl合金室温脆性的本质.研究Fe对NiAl合金缺陷电子密度的影响.
NiAl alloy has many excellent physical properties: its density is low, only 5.86g / cm ~ 3; its melting point up to 1640 ℃; it has high thermal conductivity, Ni-based superalloy 4 to 8 times; it also Has good oxidation resistance.Because these advantages of NiAl alloy, making it expected to become a new generation of high temperature structural materials, but single crystal and polycrystalline NiAl alloy is very brittle at room temperature, which hindered its current application Geoyge et al studied The results show that the microalloying of B, C and Be on NiAl alloy does not achieve the purpose of improving the ductility of NiAl alloy.The experimental results of Rachinger et al , Ni-Al alloying with Cr, Co, Fe, Mn and other elements can reduce the order of NiAl.Fe-content of Ni-20AI-30Fe after extrusion, the room temperature plastic elongation of 8% The microscopic mechanism of the effect of these alloying elements on the mechanical properties of NiAl alloys was investigated.In this paper, positron lifetime spectra of NiAl, Ni_ (48) Al_ (45) Fe_7 and Ni_ (50) Al_ (20) Fe_ (30) The nature of brittleness at room temperature.The effect of Fe on electron density of defects in NiAl alloy was investigated.