本文選題：耐高溫高熵合金 + 模擬相圖�。� 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：高熵合金是由至少四種主元形成的固溶體合金,其基本特征是混合熵高,合金相以簡(jiǎn)單固溶體為主,其綜合性能優(yōu)異,如硬度高、韌性好、良好的耐磨性和耐蝕性等。特別是在高溫條件下,高熵合金的相結(jié)構(gòu)穩(wěn)定、強(qiáng)度高,有望成為新一代高溫工程結(jié)構(gòu)材料。本文結(jié)合計(jì)算機(jī)模擬相圖(CALPHAD)、第一性原理密度泛函計(jì)算(DFT)和物化參數(shù)判據(jù),設(shè)計(jì)了NbTaV-(Ti,Mo,W)耐高溫高熵合金系,采用高真空電弧熔煉法成功制備出這五種合金,并研究了合金的鑄態(tài)微觀組織結(jié)構(gòu)、力學(xué)性能和強(qiáng)化機(jī)制。主要研究結(jié)果如下:(1)制備的NbTaTiV、NbTaVW、NbTaTiVW、MoNbTaV和MoNbTaTiV五種耐高溫高熵合金均為單相體心立方結(jié)構(gòu)固溶體。在室溫下,五種合金均呈現(xiàn)高強(qiáng)度大塑性,其中MoNbTaTiV綜合性能優(yōu)異,屈服強(qiáng)度1.4 GPa,斷裂強(qiáng)度2.45 GPa,塑性達(dá)到30%;在溫度為1273 K時(shí),NbTaTiVW的硬度是鎳基高溫合金In 718和In 718 H的2.5倍。研究表明,鈦元素的添加有利于提高合金塑性;鉬、鎢元素的添加有利于提高合金強(qiáng)度。(2)與建立在Miedema模型的物化參數(shù)判據(jù)相比,CALPHAD計(jì)算不僅可以模擬合金的平衡和非平衡相圖,還能有效地描述固相和液相的熱力學(xué)性質(zhì)隨溫度的變化,并且預(yù)測(cè)在非平衡凝固過(guò)程中合金各組元的微觀偏析。(3)NbTaV-(Ti,Mo,W)五種高熵合金的晶格常數(shù)均符合混合定律;通過(guò)DFT計(jì)算表明,每種合金的原子體積和彈性性質(zhì)(體模量和剪切模量)也符合混合定律。(4)通過(guò)統(tǒng)計(jì)多種單相體心立方結(jié)構(gòu)耐高溫高熵合金在室溫下的力學(xué)性能,發(fā)現(xiàn)合金硬度約為其屈服強(qiáng)度的三倍,合金的主要強(qiáng)化機(jī)制為固溶強(qiáng)化。建立了適用于鑄態(tài)體心立方結(jié)構(gòu)高熵合金的半經(jīng)驗(yàn)?zāi)Ｐ?可以有效預(yù)測(cè)合金的屈服強(qiáng)度和硬度。
[Abstract]:High entropy alloy is a kind of solid solution alloy formed by at least four principal components. Its basic characteristics are high mixing entropy, simple solid solution and excellent comprehensive properties, such as high hardness, good toughness, good wear resistance and corrosion resistance, etc.Especially at high temperature, the phase structure of high entropy alloy is stable and its strength is high, which is expected to become a new generation of high temperature engineering structural materials.In this paper, the high-temperature and high-entropy alloy system of NbTaV-TiTi-Mo-W has been designed by using computer simulation phase diagram (CALPHADA), first-principle density functional calculation (DFTT) and physicochemical parameter criterion. The five alloys have been successfully prepared by high vacuum arc melting.The microstructure, mechanical properties and strengthening mechanism of the as-cast alloy were studied.The main results are as follows: NbTaTiVU NbTaVWN NbTaTiVWU MoNbTaV and MoNbTaTiV five high-temperature high-entropy alloys are single-phase body-centered cubic structure solid solutions.At room temperature, all the five alloys exhibit high strength and large plasticity, of which MoNbTaTiV has excellent comprehensive properties, yield strength is 1.4GPaand fracture strength is 2.45GPa.The hardness of NbTaTiVW is 2.5 times higher than that of Ni-base superalloys in 718 and in 718H at 1273 K.The results show that the addition of titanium can improve the plasticity of the alloy, the addition of molybdenum and tungsten can improve the strength of the alloy, and the calculation of physical and chemical parameters based on the Miedema model can not only simulate the equilibrium and non-equilibrium phase diagrams of the alloy, but also improve the strength of the alloy.The thermodynamic properties of solid and liquid phases can also be described effectively with the change of temperature, and the lattice constants of five kinds of high entropy alloys, I. e., the microsegregation of each component of the alloy during nonequilibrium solidification, are all in accordance with the mixing law, and the DFT calculation shows that the lattice constants of the five kinds of high entropy alloys are in accordance with the mixing law.The atomic volume and elastic properties (bulk modulus and shear modulus) of each alloy also conform to the law of mixing.It is found that the hardness of the alloy is about three times of its yield strength, and the main strengthening mechanism of the alloy is solution strengthening.A semi-empirical model for high entropy alloys with as-cast body centered cubic structure is established, which can effectively predict the yield strength and hardness of the alloys.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG139

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相關(guān)期刊論文 前2條

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本文編號(hào)：1767958