【作者】 郑丽璇；

【导师】 李宁；

【作者基本信息】 四川大学 ， 材料加工工程， 2005， 硕士

【摘要】 本文针对TiNiNb形状记忆合金工程应用的需要,以及TiNiNb形状记忆合金管接头相变过程的计算机模拟的需要,开展了以下几个方面的研究: 1.测量模拟所需要的材料在不同温度下的比热、导热系数、弹性模量、相变热等物性参数。 2.形状记忆合金相变与温度、应力、时间之间影响机制的研究。 3.不同处理状态对合金记忆性能和力学性能的影响。 本文使用了激光脉冲法、DSC法、SEM和X-Ray衍射分析等先进的实验分析技术,而且为实现高温、低温的温度转换来达到测量回复应力的目的,改造了控温系统使其达到很好的控温精度,同时设计并制造了液氮制冷系统等试验装备。 通过对合金物性参数的测量得到,在30℃～300℃之间,Ni₄₇Ti₄₄Nb₉合金的热扩散率、比热容、弹性模量、导热系数随着温度的增加而升高。合金的平均线膨胀系数为11.43×10^-6/℃。 建立了合金约束加热时回复应力方程。试验得出,合金的预变形量越大,合金的回复应力越小;预变形温度从-90℃变化上升至-30℃,回复应力呈先上升后下降的变化趋势。非真空热处理、真空热处理这两种热处理方式的变化对回复应力σ_r^m没有很大的影响;而冷拔态下合金的回复应力值σ_r^m远远高于其他两种状态的回复应力;不同的回复加热温度,其冷却时产生的回复应力σ_r^m随加热温度的上升。预变形越大,预变形温度对可回复应变率的影响就越大,马氏更多还原

【Abstract】 This paper aims at the requirement of the engineering application of TiNiNb SMA, and the requirement of computer simulation technology in phase transformation processing of SMA pipe-connector. It unfolds these studies about several aspects thereinafter:1. Metallic thermal physics properties of SMA are measured in different temperature range. It includes specific heat, thermal diffusivity, thermal conductivity and so on in need of computer simulation study.2. The study of influencing mechanism on the relationships among phase transformation of SMA, temperature, stress and time.3. The affection of heat treatment to shape memory properties and mechanical properties of alloys.We make use of these advanced testing technology including laser flash method, DSC method, SEM and X-Ray diffracting technology, and make over controlling temperature system that have very good controlling temperature precision for measuring recovery stress between high temperature and low temperature, and design liquefied nitrogen refrigeration system and so on examination arms.Through measuring thermo physical properties, experiment indicates that thermal diffusivity, specific heat, and thermal conductivity increase with temperature increasing from 30℃ to 300℃. average linear swell factor of Ni-Ti-Nb alloy is about 11.43 X 10~-6 per centigrade.We proposed the equation to calculate the recovery stress during heating under constraints. Experiment indicates that the recovery stress σrmof alloys is decreasing with pre-strain increasing, and The movement tide of the recovery stress σrmof alloys is rising initially and declining finally with temperature of pre-strain increasing from-90 ℃ to-30℃.We find that the change of two heat treatment methods between non-vacuum heat treatment and vacuum heat treatment do not affect the recovery stress σrm, but the recovery stress σrm of cold-drawing alloys is the highest than the other two. The recovery stress σrm is increasing with recovery temperature increasing in different recovery temperature ranges. Experiment indicates that the higher the pre-strain is, the greater the influence of deformation temperature on the shape recovery ratio is, the higher martensitic anti-transformation As’ temperature is.The shape recovery ratio of alloys with non-vacuum heat treatment is the same as the one with vacuum heat treatment. The shape recovery ratio of cold-drawing alloys is the highest than the other two. Based stress relaxation’s curves, we analyzed that the phenomena on stress relaxation of alloys may not happen from 10T? to 50°C, resist- stress relaxing properties is excellent, and it has good engineering applicative foreground.Experiment indicates that, through measuring mechanical properties, the stress curves of alloys of restricting recover haven’t the evident yield band, and the stress o02of alloys of restricting recover is higher than the ones of alloys of non-restricting recover, but the stress ab of alloys of restricting recover is lower than the ones of alloys of non-restricting recover. We find that the stress ob and o02 of cold-drawing alloys are the highest than the other two (non-vacuum heat treatment and vacuum heat treatment), but its stretch ratio is lowest than the other two. With cold-drawing treatment or non-vacuum heat treatment, its stretch ratio that is about 15% to 17% can’t satisfy the require of engineering application, but the method of vacuum heat treatment can prevent oxidation effectively, its stretch ratio arrive at 36% around and is perfect.The yield stress of the recovery samples after pre-strain are higher than the ones of these original samples at 20°C,100°C and 200°C, and the stress curves of these recovery samples haven’t the evident yield band. With temperature increasing the stress ob of these samples under different states are increasing. The critical yield stress is increasing with increasing temperature and that the range of transformation hystersis is wide makes for engineering application. Above Mss temperature (Mss ^60°C ), the critical yield stress is decreasing with increasing temperature, and shape memory properties is decreasing with increasing temperature.更多还原