【作者】 孙斌；

【导师】 孟祥龙；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2013， 硕士

【摘要】 本文研究了Nb含量16-20at.%的铸态Ti-Nb合金的组织结构、马氏体相变行为、力学性能和记忆效应。随后研究了不同冷轧变形量、不同退火温度对Ti-Nb合金力学性能和记忆效应的影响，以及经热机械处理后马氏体的组织结构演化规律。研究表明，Nb含量为16-20at.%Ti-Nb铸态合金室温下组成相主要为马氏体相，其中还有少量残余母相和细小弥散的ω相。铸态Ti-Nb合金热形成马氏体变体呈自协作组态，主要呈三角形或V型。变体间呈{111}Ⅰ型孪晶关系。DSC测试结果表明，Ti-Nb合金马氏体相变及逆转变温度随着Nb含量的降低而增加，Nb含量每降低1at.%，逆相变温度升高约38℃。Nb含量最低的Ti-16Nb的马氏体相变温度为333℃。铸态Ti-Nb合金塑性很好，延伸率能达到40%；但记忆效应较差，在预应变2%时即不能获得完全的形状回复。通过冷轧加退火能有效提高Ti-Nb合金的力学性能，冷轧变形后Ti-Nb合金屈服强度升高，但塑性变差，随着退火温度的升高，Ti-Nb合金屈服强度有所下降，断裂延伸率提高。变形量为20%、30%冷轧加650℃退火后，可有效地提高合金的形状记忆效应，能获得约3%的完全可回复应变。分析表明，在马氏体状态下热机械处理对Ti-Nb合金的显微组织有显著的影响。冷轧之后Ti-16Nb合金发生不同变体的再取向，自协作组态消失，马氏体形貌呈纤维状，马氏体板条出现不同程度的弯曲。经退火处理后，马氏体变体的择优取向消失，重新出现多个取向的变体，马氏体板条逐渐恢复平直，且随着退火温度的升高，马氏体板条逐渐变得细小，650℃退火时，马氏体板条变得很短小。不同冷轧变形量的Ti-Nb合金经650℃退火后，发生位错的重新排列，并有少部分区域发生再结晶。更多还原

【Abstract】 The microstructure, martensitic transformation behavior, mechanical propertiesand shape memory effects of Ti-Nb alloys with Nb content16-20at.%were studied inthis paper. The influence of cold-rolled reduction and annealing temperature on themechanical properties and shape memory effects，and the martensite structure evolutionduring this process were also studied.The results show Ti-Nb alloys with Nb content16-20at.%were mainly martensiteat room temperature, trace of residual parent phase and fine dispersive distribution ωphase existed as well. Triangular and V-shaped is the major self-accommodationmorphology in Ti-Nb alloys. The martensite variants were {111} type twins.The martensitic transformation temperature of Ti-16Nb alloy is333℃, and themartensitic transition temperature decreases by40℃with a1at.%increase of Nbcontent.The plasticity of the Ti-Nb alloys is pretty good with elongation rate of40%, buttheir shape memory effects are poor with completed recoverable strain less than2%.Thermo-mechanical treatment can improve the mechanical properties of Ti-Nb alloy.With increasing annealing temperature, the elongation increases, the yield strength isreduced. The Ti-16Nb alloy which annealed at650℃after cold rolled can get100%shape recovery ratio with3%pre-strain.The microstructures of the cold-rolled Ti-Nb alloys are fiber-like with martensitelath warped. Martensite lath gradually restore straight after annealing at differenttemperature, and the martensite laths become smaller compared with the as-cast alloys.And the size of the martensite laths becomes smaller with increasing annealingtemperature. After annealing at650℃, fine sub-grains form via dislocationsrearrangement and in some regions recrystallization occurs.更多还原