本文關(guān)鍵詞： β鈦基形狀記憶合金 數(shù)字圖像相關(guān)技術(shù) 疲勞 裂紋擴展　出處：《湘潭大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：新型β鈦基形狀記憶合金具有對人體無潛在毒性、優(yōu)異的超彈性和優(yōu)良的生物相容性,作為植入體材料在生物醫(yī)用領(lǐng)域有著極大的應(yīng)用潛力。深入研究β鈦基形狀記憶合金低周疲勞性能以及顯微組織對其疲勞性能的影響,并進一步探討和分析在交變載荷作用下β基形狀記憶合金馬氏體相變過程,裂紋擴展與馬氏體相變之間的交互作用及其機理,為推進該類合金實用化具有重要意義。本文以具有優(yōu)異超彈性能的Ti-7.5Nb-4Mo-2Sn形狀記憶合金為研究對象,利用數(shù)字圖像相關(guān)技術(shù)對β基形狀記憶合金變形進行原位觀察,并研究其變形特性;對循環(huán)載荷作用下該合金的疲勞壽命進行了評估,分析了疲勞變形過程中顯微組織、彈性模量和超彈性能變化規(guī)律;最后對裂紋擴展過程和裂紋尖端應(yīng)變場動態(tài)演變過程進行DIC原位觀察,分析α、β相界對裂紋擴展影響機理。主要研究內(nèi)容和結(jié)論如下:(1)對Ti-7.5Nb-4Mo-2Sn合金在室溫下進行扎制,在600℃到800℃下對合金進行退火處理,對不同退火溫度下合金的顯微組織、力學(xué)性能和變形特性進行研究,結(jié)果表明:α→β相的相轉(zhuǎn)變點在700℃與800℃之間。700℃和800℃合金在室溫下表現(xiàn)超彈性能。其中700℃處理得到的合金因其細(xì)小的組織結(jié)構(gòu)和α相強化作用,表現(xiàn)出更加優(yōu)異的超彈性能。馬氏體相變起源于樣品表面,然后向樣品內(nèi)部擴展,且擴展不均勻,向有利于馬氏體相變的晶粒中擴展。(2)對不同退火溫度處理后的800℃退火處理后的Ti-7.5Nb-4Mo-2Sn合金的低周疲勞壽命進行測試,結(jié)果表明:合金表現(xiàn)出比700℃處理后合金更高的疲勞壽命。形狀記憶合金反復(fù)變形過程馬氏體相變釋放熱量,合金溫度升高,促進了β→α和β→ω相變過程。疲勞變形過程中,合金發(fā)生了先軟化后硬化現(xiàn)象。合金軟化是由于孿生合并引起的;合金后來硬化是由于疲勞次數(shù)的增加,α和ω兩相含量越來越高的緣故。(3)采用數(shù)字圖像相關(guān)方法(DIC)對Ti-7.5Nb-4Mo-2Sn合金在加載過程中裂紋擴展過程和裂紋尖端應(yīng)變場進行原位觀察。研究表明:相同加載速率下,與800℃退火處理后的合金相比,700℃退火處理的合金裂紋擴展速率和偏轉(zhuǎn)角偏高,這與700℃退火處理的合金中含有大量α相有關(guān),α、β相界易產(chǎn)生微裂紋或使得裂紋發(fā)生偏轉(zhuǎn)。從應(yīng)變云圖可以看出在預(yù)制裂紋尖端產(chǎn)生應(yīng)力集中,宏觀上表現(xiàn)為變形不均勻,馬氏體相變發(fā)生在變形較大處,裂紋沿著變形較大處擴展,馬氏體相變阻礙裂紋擴展。
[Abstract]:The new 尾 -titanium-based shape memory alloy has no potential toxicity to human body, excellent superelasticity and excellent biocompatibility. As implant material, it has great application potential in biomedical field. The low cycle fatigue properties of 尾 -Ti based shape memory alloy and the effect of microstructure on its fatigue properties are studied in depth. Furthermore, the process of martensite transformation, the interaction between crack propagation and martensite transformation and its mechanism are discussed and analyzed under alternating load. In order to promote the practical application of this kind of alloy, the Ti-7.5Nb-4Mo-2Sn shape memory alloy with excellent superelastic properties is taken as the research object in this paper. The deformation of 尾-based shape memory alloy was observed in situ by digital image correlation technique and its deformation characteristics were studied. The fatigue life of the alloy under cyclic loading was evaluated, and the changes of microstructure, elastic modulus and superelastic energy during fatigue deformation were analyzed. Finally, the crack propagation process and the dynamic evolution of the strain field at the crack tip are observed in situ by DIC and the 偽 is analyzed. The effect of 尾 phase boundary on crack growth. The main contents and conclusions are as follows: 1) the Ti-7.5Nb-4Mo-2Sn alloy is bound up at room temperature. The alloy was annealed at 600 鈩，

本文編號：1452621