發(fā)布時(shí)間：2018-06-29 02:24

  本文選題：高熵合金 + 納米壓痕　； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：高熵合金是由多種具有晶格結(jié)構(gòu)的元素(其中每種主要元素都具有較高的原子百分比,約為35%~50%)組合而成的新型合金材料。因具有較高的熵值和固溶強(qiáng)化效應(yīng),其力學(xué)性能優(yōu)于傳統(tǒng)合金。高熵合金廣泛應(yīng)用在許多領(lǐng)域,例如常被用作高溫環(huán)境下的涂層材料。因此,研究高熵合金的塑性變形機(jī)理具有重要的工程應(yīng)用背景和科學(xué)意義。采用納米壓痕實(shí)驗(yàn)研究AlCoCrFeNi高熵合金室溫下的力學(xué)行為。該納米壓痕實(shí)驗(yàn)采用連續(xù)剛度法研究了4種不同的壓入應(yīng)變率Al CoCrFeNi高熵合金的納米壓痕變形行為。結(jié)果表明,Al CoCrFeNi高熵合金的蠕變變形行為依賴于應(yīng)變率。壓痕原位掃描圖顯示,在壓頭周圍的實(shí)驗(yàn)表明沿壓頭表面向上隆起,其位置高于初始試件表面,呈現(xiàn)壓入凸起現(xiàn)象,表明壓頭壓入的位置產(chǎn)生了嚴(yán)重的局部塑性變形。在不同壓入應(yīng)變率下,其彈性模量基本上保持不變,硬度值由于壓痕尺寸效應(yīng)隨著壓入深度的增大而下降。研究了AlxCoCrFeNi高熵合金中3種不同鋁元素含量對(duì)其力學(xué)行為的影響。結(jié)果表明,當(dāng)x=1的AlCoCrFeNi高熵合金的彈性模量和硬度均大于鋁元素含量為x=0.3,0.5的AlxCoCrFeNi高熵合金的彈性模量和硬度。采用X射線衍射圖譜對(duì)Al_(0.75)CoCrFeNi高熵合金的微觀組織進(jìn)行表征。Al_(0.75)CoCrFeNi高熵合金的微觀結(jié)構(gòu)由面心立方(FCC)固溶體,和體心立方結(jié)構(gòu)(BCC)固溶體兩相組成。采用納米壓痕實(shí)驗(yàn)對(duì)Al_(0.75)CoCrFeNi高熵合金兩相的微/納米力學(xué)行為進(jìn)行研究,結(jié)果表明FCC相和BCC相的接觸模量和硬度隨著最大壓入載荷增大而隨著壓入載荷的增大而增大,在Pmax=10mN時(shí)達(dá)到最大值,之后趨于穩(wěn)定。FCC相的彈性模量大于BCC相的彈性模量,而BCC相的硬度值則大于FCC相的硬度值。FCC相和BCC相的消散塑性能隨著最大壓入載荷的增大而增大。消散塑性能與壓入載荷P之間呈現(xiàn)出冪律變化關(guān)系。在相同的壓入載荷作用下,FCC相晶胞區(qū)域的消散塑性能比BCC相晶胞區(qū)域的消散塑性能高。采用數(shù)值模擬和反分析法相結(jié)合研究AlCoCrFeNi高熵合金的微/納米力學(xué)行為。利用ABAQUS有限元軟件對(duì)AlCoCrFeNi高熵合金準(zhǔn)靜態(tài)納米壓痕實(shí)驗(yàn)進(jìn)行數(shù)值模擬,并與其納米壓痕實(shí)驗(yàn)數(shù)據(jù)對(duì)比分析,得到實(shí)驗(yàn)材料的彈塑性本構(gòu)關(guān)系。將有限元模擬得到的冪律本構(gòu)方程導(dǎo)入進(jìn)行有限元模型進(jìn)行分析,結(jié)果表明,給出的本構(gòu)方程可以較準(zhǔn)確地描述AlCoCrFeNi高熵合金的微/納米力學(xué)行為。
[Abstract]:High entropy alloy is a new alloy material composed of a variety of elements with lattice structure (each of which has a high atomic percentage, about 35%). The mechanical properties of the alloy are superior to those of the traditional alloy because of its high entropy value and solid solution strengthening effect. High-entropy alloys are widely used in many fields, such as coating materials under high temperature. Therefore, studying the plastic deformation mechanism of high entropy alloys has important engineering application background and scientific significance. The mechanical behavior of AlCoCrFeNi high entropy alloy at room temperature was studied by nano-indentation test. The nanocrystalline indentation deformation behavior of four Al CoCrFeNi high entropy alloys with different indentation strain rates was studied by continuous stiffness method. The results show that the creep deformation behavior of Al CoCrFeNi high entropy alloy depends on strain rate. The in-situ indentation scanning images show that the indentation surface is raised upward along the head surface, and its position is higher than that of the initial specimen surface, which indicates that the indentation position has serious local plastic deformation. At different indentation strain rates, the elastic modulus remains basically unchanged, and the hardness decreases with the indentation size effect increasing with the indentation depth. The effects of three different aluminum contents on the mechanical behavior of AlxCoCrFeNi high entropy alloy were studied. The results show that the modulus of elasticity and hardness of AlCoCrFeNi high entropy alloy x1 are higher than those of AlxCoCrFeNi high entropy alloy with Al content of xCoCrFeNi 0.5. The microstructure of Al _ (0.75) CoCrFeNi high entropy alloy was characterized by X-ray diffraction. The microstructure of Al _ (0.75) CoCrFeNi high entropy alloy consists of FCC solid solution and bulk centered cubic structure (BCC) solid solution. The micromechanical behavior of Al _ (0.75) CoCrFeNi high entropy alloy was investigated by nano-indentation test. The results show that the contact modulus and hardness of FCC phase and BCC phase increase with the increase of maximum indentation load and increase with the increase of indentation load. The elastic modulus of FCC phase is larger than that of BCC phase, and the hardness value of BCC phase is larger than that of FCC phase. There is a power law relation between the dissipating plastic properties and the indentation load P. Under the same pressure loading, the dissipative plastic properties of FCC phase cell region are higher than that of BCC phase cell area. The micro / nano mechanical behavior of AlCoCrFeNi high entropy alloy was studied by numerical simulation and inverse analysis. The quasi-static nano-indentation test of AlCoCrFeNi high entropy alloy was simulated by Abaqus finite element software, and compared with the experimental data of nano-indentation, the elastic-plastic constitutive relation of the experimental material was obtained. The power law constitutive equation obtained by finite element simulation is introduced into the finite element model for analysis. The results show that the proposed constitutive equation can accurately describe the micro / nano mechanical behavior of AlCoCrFeNi high entropy alloy.
【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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本文編號(hào)：2080410