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  本文選題：非晶合金 + 復合材料�。� 參考：《太原理工大學》2017年碩士論文

【摘要】：非晶合金由于其獨特的性能而受到人們極大地關(guān)注,如高強度、大的彈性極限及良好的耐腐蝕和耐磨性等。然而,在室溫加載下,由于局域剪切帶的快速擴展使塊體非晶合金常表現(xiàn)出無預警的脆性斷裂特征。為了提高塊體非晶合金的宏觀塑性,材料學者提出了制備非晶復合材料的方法,即通過內(nèi)生或者外添加的方法向非晶基體中引入韌性的第二相,進而可以有效的阻止剪切帶的快速擴展。近些年,研究人員成功地制備出一系列樹枝晶增強的非晶復合材料,如Ti基和Zr基非晶復合材料。但是這類非晶復合材料由于在室溫下缺少加工硬化機制會表現(xiàn)出應變軟化的特征,這樣極大地限制了其在工程上的應用。近幾年,這個問題在B2相增強的CuZr基非晶復合材料中得到了成功的解決。B2 CuZr相在應力的誘導下可以發(fā)生馬氏體相變轉(zhuǎn)變?yōu)榫哂袉涡苯Y(jié)構(gòu)的B19?相,這樣極大地補償了非晶基體在塑性變形過程中產(chǎn)生的應變軟化,從而提高了材料的加工硬化能力。本論文以Cu Zr基非晶復合材料作為研究對象,研究了微量元素Ni對其玻璃形成能力的影響。在此基礎上,系統(tǒng)地研究了CuZr基非晶復合材料室溫下的力學行為及其獨特的變形機制。但是高溫下的力學性能也是考量其能否作為工程結(jié)構(gòu)材料的必要條件,因此對CuZr基非晶復合材料在過冷液相區(qū)內(nèi)的流變行為進行了研究與探討。本文的主要研究內(nèi)容及結(jié)論如下:(1)Ni可以有效地改變Zr48Cu48-xAl4Nix的玻璃形成能力,進而改變析出b2cuzr相的體積分數(shù)。隨著ni含量從0-1%的添加,球形b2-cuzr相的體積分數(shù)增加,當ni含量添加至1%時,b2-cuzr晶體相的體積分數(shù)達到33%,隨著ni含量的繼續(xù)增加,該非晶復合材料的玻璃形成能力增強,b2相體積分數(shù)下降。(2)在壓縮載荷下,zr48cu48-xal4nix優(yōu)異的塑性變形行為歸因于b2cuzr相的馬氏體轉(zhuǎn)變及b2cuzr相對剪切帶的阻礙作用;而單軸拉伸時沒有觀察到明顯的塑性變形,即b2cuzr相沒有起到改善塑性變形能力的作用。塑性應變拉壓不對稱的本征原因在于非晶基體的塑性區(qū)尺寸與b2cuzr相顆粒尺寸及間距在拉伸載荷下不滿足尺寸匹配關(guān)系。(3)cuzr基非晶復合材料在過冷液相區(qū)內(nèi)的變形行為對溫度和應變速率較為敏感,隨著溫度的升高和應變速率的降低,應力的峰值及開始進入塑性流變的應力明顯降低。(4)cuzr基非晶復合材料在過冷液相區(qū)內(nèi)的流變應力較高,這與其在過冷液相區(qū)內(nèi)非晶基體的晶化行為及馬氏體相變有關(guān)。鑄態(tài)時存在的及基體發(fā)生晶化后形成的b2cuzr相可以在熱與應力的作用轉(zhuǎn)變?yōu)閎19'馬氏體相,其硬度值明顯增加。因此針對過冷液相區(qū)內(nèi)cuzr基非晶復合材料與樹枝晶增強的非晶復合材料塑性流變行為的比較就相當于在室溫下“軟”的非晶基體和b2cuzr相與“硬”的b19'馬氏體相形成的非晶復合材料與“軟”的非晶基體與“硬”的樹枝晶形成的非晶復合材料的塑性流變行為的比較。因此盡管cuzr基非晶復合材料中晶體的體積分數(shù)較樹枝晶低,但是兩種非晶復合材料在過冷液相區(qū)內(nèi)表現(xiàn)出來的綜合塑性流變應力相差較小。(5)動態(tài)沖擊下,cuzr基非晶復合材料的塑性應變急劇下降,歸因于B2 Cu Zr相在有限的時間內(nèi)不能阻止剪切帶的快速擴展。另外,通過對實驗數(shù)據(jù)進行擬合得出該材料的應變速率敏感性為-0.51,主要是由于Cu Zr基非晶復合材料中非晶基體的絕熱軟化造成的。
[Abstract]:Amorphous alloys have attracted great attention due to their unique properties, such as high strength, large elastic limit and good corrosion resistance and wear resistance. However, under room temperature loading, the rapid expansion of the local shear band makes the bulk amorphous alloy exhibit a non early-warning brittle fracture characteristic. In order to improve the macrostructure of the bulk amorphous alloy, In view of the plasticity, the material scholars have proposed a method of preparing amorphous composites, that is, introducing ductile second phase into the amorphous matrix by endogenous or external additions, which can effectively prevent the rapid expansion of the shear band. In recent years, the researchers have successfully prepared a series of amorphous composite with dendrite enhancement, such as Ti based and Zr Basic Amorphous Composites. However, this type of Amorphous Composites, due to the lack of working hardening at room temperature, shows the characteristics of strain softening, which greatly restricts its engineering application. In recent years, this problem has been successfully induced in the B2 phase enhanced CuZr Based Amorphous Composites to induce the stress induction of the.B2 CuZr phase. The transformation of martensitic transformation into a monocline structure of B19? Phase can greatly compensate the strain softening of the amorphous matrix during the plastic deformation process, thus improving the ability of material processing and hardening. In this paper, the Cu Zr based amorphous composite was used as the research object to study the glass formation ability of the trace element Ni. On this basis, the mechanical behavior and the unique deformation mechanism of CuZr Base Amorphous Composites at room temperature are systematically studied. However, the mechanical properties at high temperature are also the necessary conditions to consider whether it can be used as a structural material. Therefore, the rheological behavior of CuZr Based Amorphous Composites in the supercooled liquid phase region is studied. The main contents and conclusions of this paper are as follows: (1) Ni can effectively change the glass formation ability of Zr48Cu48-xAl4Nix and then change the volume fraction of the precipitated b2cuzr phase. With the addition of Ni content from 0-1%, the volume fraction of the spherical b2-cuzr phase increases. When the content of Ni is added to 1%, the volume fraction of the b2-cuzr crystal phase reaches 33%, with the volume fraction of the b2-cuzr crystal phase up to 33%. With the increase of Ni content, the glass forming ability of the amorphous composite is enhanced and the volume fraction of B2 phase decreases. (2) the excellent plastic deformation behavior of zr48cu48-xal4nix is attributed to the martensitic transformation of the b2cuzr phase and the hindering effect of b2cuzr relative shear zone under the compression load, while the apparent plastic deformation is not observed during the uniaxial tensile. The b2cuzr phase does not play a role in improving the plastic deformability. The intrinsic reason for the asymmetry of the plastic strain tension is that the size of the plastic zone of the amorphous matrix and the particle size and spacing of the b2cuzr phase do not meet the size matching relationship under the tensile load. (3) the deformation behavior of the CuZr Based Amorphous Composites in the supercooled liquid phase is to the temperature and the strain change It is more sensitive, with the increase of temperature and the decrease of the strain rate, the stress peak and the stress that begin to enter the plastic flow obviously decrease. (4) the rheological stress of the CuZr based amorphous composite in the supercooled liquid phase is higher, which is related to the crystallization behavior and martensitic transformation in the amorphous matrix in the supercooled liquid phase. The b2cuzr phase formed after the crystallization of the matrix can change into b19'martensitic phase in the effect of heat and stress, and its hardness value increases obviously. Therefore, the comparison of the plastic rheological behavior of CuZr Based Amorphous Composites and dendrite reinforced Amorphous Composites in the supercooled liquid phase is equivalent to the "soft" amorphous matrix and b2cu at room temperature. The Zr phase is compared with the plastic rheological behavior of the amorphous composite formed by the "hard" b19'martensite phase and the amorphous matrix formed by the "soft" amorphous matrix and the "hard" dendrite. Therefore, although the volume fraction of the crystal in the CuZr base amorphous composite is lower than that of the dendrite, it is the two amorphous composite in the supercooled liquid phase region. In the dynamic impact, the plastic strain of CuZr based amorphous composite decreases sharply and the B2 Cu Zr phase can not prevent the rapid expansion of the shear band in a limited time. In addition, the sensitivity of the strain rate sensitivity of the material is -0.51 by fitting the experimental data. It is due to adiabatic softening of amorphous matrix in Cu Zr Based Amorphous Composites.

【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG139.8

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相關(guān)期刊論文 前3條

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本文編號：1820763