本文選題：Ni-Ti基薄膜　切入點(diǎn)：沉積溫度　出處：《南京大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：Ni-Ti基合金薄膜由于具有優(yōu)異的形狀記憶性和偽彈性等特性被廣泛地應(yīng)用于微機(jī)電系統(tǒng)(MEMS)中。隨著微電子器件向微型化的方向不斷發(fā)展,薄膜的特征尺寸(如薄膜厚度、晶粒尺寸等)持續(xù)減小,其相變行為和力學(xué)特性表現(xiàn)出強(qiáng)烈的尺寸依賴性,甚至出現(xiàn)反常的物理與力學(xué)特性,導(dǎo)致無法正確預(yù)測微電子器件的工作可靠性與壽命；另一方面,Ni-Ti基合金薄膜的相變行為和力學(xué)特性與組元、成分和熱處理工藝密切相關(guān)。因此,研究Ni-Ti基合金薄膜的特征尺寸、組元等對(duì)其相變行為和力學(xué)特性的影響,對(duì)設(shè)計(jì)和制備具有響應(yīng)快、相變溫度高和力學(xué)性能優(yōu)異的形狀記憶合金薄膜具有重要的科學(xué)意義�；谝陨峡紤],本文采用直流磁控濺射法,通過改變沉積溫度和退火溫度制備了一系列的三元Ni-Ti-Al薄膜和Ti/Ni多層膜。利用能譜分析、X射線衍射、掃描電子顯微鏡和透射電子顯微鏡等方法表征薄膜的化學(xué)組成、相組成和微觀結(jié)構(gòu)；利用四探針電阻測試法研究了薄膜的相變行為；利用納米壓痕法表征薄膜的偽彈性、硬度、模量和應(yīng)變速率敏感性等力學(xué)特性；研究了薄膜特征尺寸(晶粒尺寸、多層膜的調(diào)制周期)、壓痕深度、析出相和應(yīng)變速率等對(duì)Ni-Ti基合金薄膜相變行為和力學(xué)性能的影響及其作用機(jī)制。主要結(jié)論如下：(1)制備了具有高偽彈性的L21相-N143Ti3gAl19合金薄膜,發(fā)現(xiàn)薄膜的偽彈性和硬度表現(xiàn)出明顯的尺寸依賴性。其偽彈性隨晶粒尺寸和壓入深度的減小而逐漸增高,在晶粒尺寸最小為12 nm和壓痕深度最小為30nm時(shí)達(dá)到最高值92.7%。薄膜的偽彈性隨晶粒尺寸的減小而增加的原因是應(yīng)力誘導(dǎo)的馬氏體轉(zhuǎn)變所需的彈性應(yīng)變和臨界應(yīng)力隨晶粒尺寸的減小而增加。隨著晶粒尺寸從28nm減小至12 nm,薄膜的硬度先增加后減小,在晶粒尺寸為16 nm時(shí)達(dá)到最大值13.8 GPa,在晶粒尺寸≤16 nm時(shí),薄膜硬度隨晶粒尺寸展現(xiàn)出反Hall-Petch效應(yīng)。(2)發(fā)現(xiàn)富Ni析出相的生長能明顯提高Ni-Ti-Al合金薄膜的馬氏體相變溫度和硬度、減小其相變滯后。不同沉積溫度制備的Ni49.7Ti45.3Al5薄膜的馬氏體相變開始溫度均高于室溫,隨著富Ni析出相的生長,馬氏體相變溫度逐漸升高、馬氏體相變滯后溫度減小了一半、二階的B2→R→B19'相變路徑轉(zhuǎn)變?yōu)榱薆2→B19'一階相變。隨著富Ni析出相的生長,Ni44Ti32Al24合金薄膜的馬氏體相變溫度由-37.5℃增加到-33.7℃,且相變展現(xiàn)出零相變滯后。由于富Ni析出相的強(qiáng)化作用,Ni49.7Ti45.3Al5和Ni44Ti32Al24合金薄膜的硬度隨著富Ni析出相的生長分別增加了12.8%和22%。(3)通過Ti/Ni多層膜設(shè)計(jì),選用原位加熱沉積和退火處理相結(jié)合,制備出超高硬度的Ni-Ti合金薄膜,這證實(shí)了最初引入界面實(shí)現(xiàn)性能強(qiáng)化的設(shè)想。退火態(tài)Ti/Ni多層膜的合金化和力學(xué)性能都明顯依賴于薄膜的調(diào)制周期,隨著調(diào)制周期減小至5.4 nm,多層膜實(shí)現(xiàn)了充分合金化,層界面消失。沉積態(tài)和退火態(tài)的Ti/Ni多層膜的硬度都隨調(diào)制周期的減小先增大后減小,均在調(diào)制周期為5.4 nm時(shí)達(dá)到最大值。隨著壓入深度的增加,調(diào)制周期為13.5和27 nm的多層膜的硬度出現(xiàn)異常軟化,可以發(fā)現(xiàn)其載荷-位移曲線上產(chǎn)生了明顯的"pop-in"和載荷急劇下降現(xiàn)象。"pop-in"和載荷下降現(xiàn)象由應(yīng)力誘導(dǎo)的馬氏體相變引起,同時(shí)誘導(dǎo)馬氏體相變的臨界載荷隨著調(diào)制周期的減小而增加。(4)研究了應(yīng)變速率對(duì)退火態(tài)Ti/Ni多層膜力學(xué)性能和相變行為的影響。發(fā)現(xiàn)調(diào)制周期為13.5和27 nm的退火態(tài)Ti/Ni多層膜的硬度具有負(fù)的應(yīng)變速率敏感性,而其他調(diào)制周期的多層膜的硬度不隨應(yīng)變速率變化。應(yīng)力誘導(dǎo)的馬氏體相變是調(diào)制周期為13.5和27 nm的退火態(tài)Ti/Ni多層膜的硬度出現(xiàn)負(fù)的應(yīng)變速率敏感性的內(nèi)在原因。另外,發(fā)現(xiàn)引起馬氏體相變的臨界載荷隨應(yīng)變速率的加快而逐漸增大,這是由于應(yīng)變速率越快,更多的相變(奧氏體-馬氏體相變)潛熱來不及消散,這有利于奧氏體相保持穩(wěn)定,導(dǎo)致驅(qū)動(dòng)相變所需的應(yīng)力變大。
[Abstract]:Ni-Ti based alloy film with shape memory and pseudo elastic properties excellent is widely used in microelectromechanical systems (MEMS). With the continuous development of microelectronic devices to miniaturization, the feature size of films (such as film thickness, grain size, etc.) continued to decrease and the phase behavior and mechanical properties a strong dependence on the size of the physical and mechanical properties, and even lead to abnormal work, can not correctly predict the reliability and life of microelectronic devices; on the other hand, Ni-Ti based alloy thin film phase transition behavior and mechanical properties of the element composition and heat treatment process are closely related. Therefore, the feature size of Ni-Ti based alloy thin films so, component effect on the phase behavior and mechanical properties, the design and preparation of fast response, high phase transition temperature and excellent mechanical properties of shape memory alloy film has an important branch Significance. Based on the above considerations, this paper by DC magnetron sputtering by changing the deposition temperature and annealing temperature to prepare a series of three Ni-Ti-Al films and Ti/Ni multilayers. The energy spectrum analysis, chemical composition of X ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the phase composition and film. Micro structure; phase behavior of thin films are studied by using four probe method; using pseudo elasticity, by nanoindentation hardness, modulus and mechanical properties of strain rate sensitivity; studied feature size (the modulation period of multilayers grain size), indentation depth, precipitation and strain rate, etc. the phase transition behavior of Ni-Ti based alloys and the mechanical properties and mechanism. The main conclusions are as follows: (1) with high pseudo elastic L21 phase -N143Ti3gAl19 alloy thin film was prepared and found thin The film of the pseudo elasticity and hardness show obvious size dependence. The pseudo elasticity with the grain size and the penetration depth decreases gradually increased, reached the highest value of pseudo elastic 92.7%. films in the minimum grain size of 12 nm minimum and indentation depth is 30nm with the decrease of grain size and the reasons for the increase of martensite change of stress induced required elastic strain and the critical stress increases with the decrease of the grain size. The grain size decreases from 28nm to 12 nm, the hardness of the film increased first and then decreased, the grain size of 16 nm reaches the maximum value of 13.8 GPa in grain size less than 16 nm, the hardness of the films as the grain size showed anti Hall-Petch effect. (2) found that Ni rich precipitates can significantly improve the growth of Ni-Ti-Al alloy films on martensitic transformation temperature and hardness, reduce the hysteresis. Ni49.7Ti45.3Al5 thin films prepared by different deposition temperature The starting temperature of martensitic transformation was higher than that at room temperature, with the growth of Ni rich precipitates, the martensitic transformation temperature increased gradually, the martensitic transformation temperature hysteresis is reduced by half, B19'transition path of order two B2 - R - B2 - B19' transformation to a first-order phase transition. With rich Ni precipitates the growth of martensite the phase transition temperature of Ni44Ti32Al24 alloy film increased from -37.5 DEG to -33.7 DEG, and the phase change show zero hysteresis. Due to the strengthening effect of Ni rich precipitates, Ni49.7Ti45.3Al5 and Ni44Ti32Al24 alloy films with hardness of Ni rich precipitates growth were increased by 12.8% and 22%. (3) through the design of Ti/Ni multilayer film, using in situ heating deposition and annealing treatment, preparation of ultrafine Ni-Ti alloy films with high hardness, which confirmed the initial introduction of the interface to realize performance enhancement. And the mechanical properties of the alloy annealed Ti/Ni films have obvious dependence The modulation period on film, with the modulation period is reduced to 5.4 nm, multilayer achieved full alloying layer interface disappeared. Ti/Ni multilayer films deposited and annealed hardness with the decrease of modulation period increased first and then decreased in the modulation period is reached the maximum value of 5.4 nm. With the increase of pressure the depth of the modulation period of multilayers of 13.5 and 27 nm the hardness of abnormal softening, can be found that the load displacement curve has obvious "pop-in" and a sharp decline in load phenomenon. "Pop-in" decreases and the load phenomenon caused by the martensite transformation induced by stress, critical load and induced martensitic transformation increased with the decrease of modulation period. (4) studied the effect of strain rate on the properties and phase behavior of annealed Ti/Ni films annealed Ti/Ni mechanics. Found that multilayer modulation period is 13.5 and 27 nm hardness has a negative The strain rate sensitivity, and other periodic multilayer film hardness with strain rate change. The martensitic transformation is induced by the annealed Ti/Ni multilayer modulation period of 13.5 and 27 nm, the hardness of the negative strain rate sensitivity of the intrinsic reason. In addition, that leads to the critical load of martensite phase transition when the strain rate is accelerated gradually increases. This is due to the strain rate is faster, more phase (austenite martensite transformation) to latent heat dissipation, which is conducive to maintain the stability of austenite phase, resulting in the stress driven phase transition required larger.

【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB383.2

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本文編號(hào)：1629614