發(fā)布時(shí)間：2018-05-13 16:39

  本文選題：氧化鋯 + 納米壓入　； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：氧化鋯陶瓷因其具有高強(qiáng)度、高硬度和相變?cè)鲰g等特性,已成為一種重要的工程材料,而其力學(xué)行為及變形機(jī)理成為相關(guān)學(xué)者研究的熱點(diǎn)。本文基于納米壓入實(shí)驗(yàn)方法研究了氧化鋯(Ce-TZP)陶瓷在壓入過程中相變與其力學(xué)性能的關(guān)系,并通過分子動(dòng)力學(xué)方法模擬了壓入過程中壓頭尖端單斜氧化鋯晶體的變形行為過程,對(duì)其變形過程中的原子組態(tài)和原子位錯(cuò)的變化情況進(jìn)行了研究。(1)在連續(xù)剛度測(cè)量模式下,分別在不同應(yīng)變率下等壓入深度和等應(yīng)變率不同壓入深度條件下對(duì)Ce-TZP進(jìn)行了納米壓入測(cè)試,根據(jù)Reuss理論推導(dǎo)出一種確定納米壓入過程中Ce-TZP中單斜相體積分?jǐn)?shù)的方法,并結(jié)合XRD分析驗(yàn)證了其可靠性。結(jié)果表明,受壓入過程中相變行為的影響,在加載階段氧化鋯表現(xiàn)出一定的應(yīng)變率敏感性,相變?cè)鲰g機(jī)制對(duì)其力學(xué)性能有顯著影響;而其彈性模量的改變主要受t→m相變過程中所形成的單斜相影響,彈性模量和單斜相體積分?jǐn)?shù)隨著壓入深度增加而呈相反的規(guī)律。在相同壓深條件下,單斜相體積分?jǐn)?shù)隨著應(yīng)變率增加而降低。(2)在Lewis等提出的對(duì)勢(shì)理論和Wolf等提出的系統(tǒng)庫(kù)倫勢(shì)能理論的基礎(chǔ)上建立氧化鋯單斜晶體的分子動(dòng)力學(xué)模型,用以模擬納米壓入實(shí)驗(yàn)過程中壓頭尖端單斜相氧化鋯的變形及力學(xué)行為。結(jié)果表明壓入過程中產(chǎn)生的載荷波動(dòng)是由基體內(nèi)部原子堆垛和位錯(cuò)變化引起;對(duì)單斜相晶體不同方向的壓入會(huì)在其內(nèi)部產(chǎn)生不同的滑移面,且在壓入過程中載荷間斷下降的原因也不相同。不同壓入速率下載荷位移曲線在彈性段重合,在塑性段展現(xiàn)了一定的率相關(guān)性特征;低壓入速率下由于應(yīng)力馳豫P-h曲線會(huì)表現(xiàn)出明顯的應(yīng)變硬化和載荷波動(dòng)現(xiàn)象。
[Abstract]:Zirconia ceramics have become an important engineering material because of its high strength, high hardness and phase transformation toughening. The mechanical behavior and deformation mechanism of zirconia ceramics have become the focus of research. In this paper, the relationship between phase transition and mechanical properties of Zirconia Ce-TZP ceramics during indentation is studied based on the experimental method of nano-indentation. The deformation behavior of monoclinic zirconia crystal at the tip of the indenter is simulated by molecular dynamics method. The atomic configuration and the change of atomic dislocation in the deformation process are studied. Nano-indentation tests of Ce-TZP were carried out under the condition of equal indentation depth and equal strain rate at different strain rates. According to Reuss theory, a method for determining monoclinic volume fraction in Ce-TZP was deduced. The reliability is verified by XRD analysis. The results show that the zirconia exhibits a certain strain rate sensitivity during loading, and the toughening mechanism of phase transition has a significant effect on the mechanical properties of zirconia. The change of elastic modulus is mainly affected by the monoclinic phase formed during the t m phase transition. The elastic modulus and the volume fraction of monoclinic phase show the opposite law with the increase of indentation depth. Under the same pressure condition, the monoclinic phase volume fraction decreases with the increase of strain rate. The molecular dynamics model of zirconia monoclinic crystal is established on the basis of the counter potential theory proposed by Lewis et al and the system Coulomb potential energy theory proposed by Wolf et al. The deformation and mechanical behavior of monoclinic zirconia at the tip of the head were simulated. The results show that the load fluctuation in the process of indentation is caused by the changes of atoms stacking and dislocations in the matrix, and the different slip planes are produced in the different directions of the monoclinic crystals. The reasons for the continuous decrease of load in the process of indentation are also different. The loading displacement curve of different indentation rates overlapped in the elastic section and showed a certain rate correlation in the plastic section, and the P-h curve showed obvious strain hardening and load fluctuation phenomenon at low pressure entry rate due to stress relaxation.
【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)】：TQ174.1

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