【摘要】：馬氏體相變的研究已近百年,現(xiàn)已廣泛的應用于工程領域。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理至今仍不很完善。馬氏體相變理論研究的進展將推動馬氏體的應用,因此對孿晶機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生本征應變,從而產生自適應彈性場,彈性場將反過來影響孿晶構型的生長。本文將以馬氏體微觀結構及自適應現(xiàn)象為研究背景,通過有限元方法計算不同構型下彈性應力和應變場,旨在探明由本征應變導致的彈性場與馬氏體孿晶構型的關系。本文基于文獻中Hane和Shield的數(shù)據(jù)構建了奧氏體-孿晶馬氏體及楔形孿晶馬氏體兩類構型,并通過弱形式自行編寫了Freefem++代碼對兩類構型中的彈性場進行了有限元分析。對于奧氏體-孿晶馬氏體構型,針對固定邊界、自由邊界和彈性邊界下構型的彈性應力場進行了分析,結果表明孿晶的形成對應變能有減小作用。同時,相界面處本征應變的分布方式對應力場的分布具有很大影響,分析表明以梯度方式變化的本征應變可有效減少體系的彈性能。而對于楔形矛尖狀孿晶馬氏體,針對相同構型下的不同體積分數(shù)的楔形孿晶構型的剪應力場進行分析,發(fā)現(xiàn)隨著孿晶體積分數(shù)的增長,沿慣習面的最大剪應力會先增大后減小,這表明馬氏體的生長在一定階段后將因為自身產生的彈性場而被抑制。沿慣習面剪應力的分析還表明馬氏體相變以沿慣習面擴張的方式進行。
[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.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG139.6

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本文編號：2433795