發(fā)布時(shí)間：2019-03-03 14:47

【摘要】：馬氏體相變的研究已近百年,現(xiàn)已廣泛的應(yīng)用于工程領(lǐng)域。CuAlNi形狀記憶合金的優(yōu)秀性能就是基于熱彈性馬氏體中的微觀組織,但其中相變孿晶的形成機(jī)理至今仍不很完善。馬氏體相變理論研究的進(jìn)展將推動(dòng)馬氏體的應(yīng)用,因此對(duì)孿晶機(jī)制的深入研究十分重要。本文研究的基本思想如下：馬氏體相變中由于原子晶格改變將產(chǎn)生本征應(yīng)變,從而產(chǎn)生自適應(yīng)彈性場(chǎng),彈性場(chǎng)將反過來影響孿晶構(gòu)型的生長。本文將以馬氏體微觀結(jié)構(gòu)及自適應(yīng)現(xiàn)象為研究背景,通過有限元方法計(jì)算不同構(gòu)型下彈性應(yīng)力和應(yīng)變場(chǎng),旨在探明由本征應(yīng)變導(dǎo)致的彈性場(chǎng)與馬氏體孿晶構(gòu)型的關(guān)系。本文基于文獻(xiàn)中Hane和Shield的數(shù)據(jù)構(gòu)建了奧氏體-孿晶馬氏體及楔形孿晶馬氏體兩類構(gòu)型,并通過弱形式自行編寫了Freefem++代碼對(duì)兩類構(gòu)型中的彈性場(chǎng)進(jìn)行了有限元分析。對(duì)于奧氏體-孿晶馬氏體構(gòu)型,針對(duì)固定邊界、自由邊界和彈性邊界下構(gòu)型的彈性應(yīng)力場(chǎng)進(jìn)行了分析,結(jié)果表明孿晶的形成對(duì)應(yīng)變能有減小作用。同時(shí),相界面處本征應(yīng)變的分布方式對(duì)應(yīng)力場(chǎng)的分布具有很大影響,分析表明以梯度方式變化的本征應(yīng)變可有效減少體系的彈性能。而對(duì)于楔形矛尖狀孿晶馬氏體,針對(duì)相同構(gòu)型下的不同體積分?jǐn)?shù)的楔形孿晶構(gòu)型的剪應(yīng)力場(chǎng)進(jìn)行分析,發(fā)現(xiàn)隨著孿晶體積分?jǐn)?shù)的增長,沿慣習(xí)面的最大剪應(yīng)力會(huì)先增大后減小,這表明馬氏體的生長在一定階段后將因?yàn)樽陨懋a(chǎn)生的彈性場(chǎng)而被抑制。沿慣習(xí)面剪應(yīng)力的分析還表明馬氏體相變以沿慣習(xí)面擴(kuò)張的方式進(jìn)行。
[Abstract]:The study of martensitic transformation has been studied for nearly 100 years and has been widely used in engineering field. The excellent properties of CuAlNi shape memory alloy are based on the microstructure of thermoelastic martensite, but the formation mechanism of transformation twins is still not perfect. The development of martensitic transformation theory will promote the application of martensite, so it is very important to study the twinning mechanism in depth. The basic ideas studied in this paper are as follows: in martensitic transformation, due to the change of atomic lattice, the intrinsic strain will be generated, and thus an adaptive elastic field will be generated, which in turn will affect the growth of twin configurations. In this paper, based on the microstructure and self-adaptive phenomena of martensite, the elastic stress and strain fields under different configurations are calculated by finite element method in order to find out the relationship between the elastic field caused by intrinsic strain and the twin configuration of martensite. Based on the data of Hane and Shield, two configurations of austenite-twin martensite and wedge-shaped twin martensite have been constructed in this paper, and the elastic fields in the two configurations have been analyzed by using the Freefem code compiled by themselves in weak form. For the austenite-twin martensite configuration, the elastic stress field of the configuration at fixed boundary, free boundary and elastic boundary is analyzed. The results show that the formation of twin has a decreasing effect on the strain energy. At the same time, the distribution mode of the intrinsic strain at the interface has a great influence on the distribution of the stress field. The analysis shows that the intrinsic strain with gradient mode can effectively reduce the elastic energy of the system. For the wedge-shaped twin martensite, the shear stress field of the wedge-shaped twin configuration with different volume fraction under the same configuration is analyzed. It is found that the maximum shear stress along the habitual plane increases first and then decreases with the increase of the volume fraction of the twin. This indicates that the growth of martensite at a certain stage will be inhibited by its own elastic field. The analysis of shear stress along the customary plane also shows that the martensitic transformation takes place along the customary plane.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG139.6

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本文編號(hào)：2433795