【作者】 杨军；

【导师】 贺志荣；

【作者基本信息】 陕西理工学院 ， 材料加工工程， 2011， 硕士

【摘要】 本文以Ti-50.8Ni、Ti-50.8Ni-0.3Cr和Ti-51.1Ni形状记忆合金（SMA）为研究对象,用光学显微镜、热重分析仪、X射线衍射仪、示差扫描量热仪和拉伸实验,研究了Cr掺杂及热处理对Ti-Ni SMA组织、相变、低温形变和室温循环形变特性的影响规律。研究结果表明:三种合金室温相组成主要为母相B2（CsCl型晶体结构）,且低温和中温退火后的形变组织呈纤维状,随退火温度（θ_a）升高,纤维组织逐渐演变为等轴晶粒,当θ_a超过600℃后,三合金氧化加剧。随θ_a升高,Ti-50.8Ni合金冷却/加热相变类型由A→R→M / M→R→A型向A→R→M / M→A型再向A→M / M→A型转变;Ti-50.8Ni-0.3Cr合金的相变类型由A→R / R→A型向A→R→M / M→R→A型向A→R→M / M→A型再向A→M / M→A型转变;而Ti-51.1Ni合金的相变类型由A→R / M→R→A型向A→R→M / M→R→A型再向A→M / M→A转变。三合金R相变温度和M相变热滞降低,M相变温度升高,R相变热滞变化不大,保持在4℃左右。此外,随θ_a升高,三合金应力-应变曲线上平台应力先降低后升高,抗拉强度降低,塑性和一次能耗（WD）增加。在较低温度（10℃）变形时,400-500℃退火态Ti-50.8Ni和Ti-51.1Ni合金呈形状记忆效应（SME）特性,550-650℃退火时呈SME+超弹性（SE）特性;400-650℃退火态Ti-50.8Ni-0.3Cr合金则呈SE特性。在室温和10℃循环变形时,随循环变形次数n增加,Ti-50.8Ni和Ti-51.1Ni合金由SME演变为线性SE,平台应力和积累残余应变（ε_r^*）迅速增加;Ti-50.8Ni-0.3Cr合金由非完全超弹性演变为完全超弹性,合金的超弹性应力-应变曲线形态较稳定。随n增加,Ti-50.8Ni和Ti-51.1Ni合金的超弹性残余应变（ε_r）减小,超弹性应变恢复率（η_s）增加;Ti-50.8Ni-0.3Cr合金的ε_r和η_s则分别稳定在较低和较高水平,显示出良好的超弹性稳定性。随n增加,Ti-50.8Ni和Ti-51.1Ni合金的当量刚度(k_eq)先增加后趋于稳定,WD先快速增加后减小,当量阻尼系数(ξ_eq)则迅速减小;Ti-50.8Ni-0.3Cr合金的k_eq和WD比较稳定,ξ_eq先减小后趋于稳定。随θ_a升高,Ti-50.8Ni和Ti-51.1Ni合金弹簧由SME过渡到SE,而Ti-50.8Ni-0.3Cr合金弹簧则始终呈现SE,且三合金弹簧的平台应力先降低后升高。提出了一种基于形状记忆合金弹簧驱动的温敏开关装置设计方法,为温敏新产品的开发设计提供了一种新思路。更多还原

【Abstract】 The effects of adding Cr and heat treatment on the microstructure, transformation, low temperature deformation and room temperature cyclic deformation characteristics of Ti-Ni shape memory alloys （SMA） were investigated by optical microscope, thermo-gravimetric, X-ray diffraction, differential scanning calorimetry and tensile test using Ti-50.8Ni, Ti-50.8Ni-0.3Cr and Ti-51.1Ni SMAs as the samples in this paper. The results are as follows:The composition phases of Ti-50.8Ni, Ti-50.8Ni-0.3Cr and Ti-51.1Ni alloys are parent phase （B2） （CsCl structure）, and the low and intermediate temperature annealed Ti-50.8Ni, Ti-50.8Ni-0.3Cr and Ti-51.1Ni alloys’deforming microstructures are fibrous. With increasing the annealing temperature （θ_a）, the fibrous microstructure evolves gradually to equiaxed grain. The oxidation of this there alloys speeds up whenθ_a is over 600℃.With increasingθ_a, the transformation types of Ti-50.8Ni alloy change from A→R→M / M→R→A to A→R→M / M→A to A→M / M→A （A-parent phase, R-R phase, M-martensite）, and one of Ti-50.8Ni-0.3Cr alloy change from A→R / R→A to A→R→M / M→R→A to A→R→M / M→A to A→M / M→A upon cooling / heating, and the types of Ti-51.1Ni alloy change from A→R→M / M→R→A to A→R→M / M→A upon cooling / heating. With increasingθ_a, the R transformation temperatures and M temperature hysteresises decrease, the M transformation temperatures increase, and R temperature hysteresises are nearly not change as about 4℃for Ti-50.8Ni, Ti-50.8Ni-0.3Cr and Ti-51.1Ni alloys. With increasingθ_a, the platform-stress （σ_m） in the stress-strain curves decreases firstly and then increases, tensile strength decreases, ductility and energy loss per cycle （WD） increase for Ti-50.8Ni, Ti-50.8Ni-0.3Cr and Ti-51.1Ni alloys. When deforms at low temperature （10℃）, the 400-500℃annealed Ti-50.8Ni and Ti-51.1Ni alloys show shape memory effect （SME）, the 550-650℃annealed ones show SME + superelasticity （SE）, while the 400-650℃annealed Ti-50.8Ni-0.3Cr alloy shows SE.When cyclic deformation at room temperature and low temperature （10℃）, the characteristics of Ti-50.8Ni and Ti-51.1Ni alloys evolved from SME to linear SE, and the stress inducing martensitic critical stress and the accumulation residual strain （ε_r^*） increased rapidly with increasing cyclic deformation number n, while the characteristics of Ti-50.8Ni-0.3Cr alloy evolved from incomplete superelasticity to complete superelasticity, and the shape of stress-strain curve is stable. With increasing n, the superelastic residual strain （ε_r） decreased and the superelastic strain recovery ratio （η_s） increased in Ti-50.8Ni and Ti-51.1Ni alloys; while theε_r andη_s in Ti-50.8Ni-0.3Cr alloy kept at lower and higher values, respectively. The superelasticity of Ti-50.8-0.3Cr alloy was stable.With increasing n, the equivalent stiffness (k_eq) of Ti-50.8Ni and Ti-51.1Ni alloy increase firstly and then tend to constant, the WD increases firstly and then decreases, and the equivalent damping (ξ_eq) decreases. While the k_eq and WD of Ti-50.8-0.3Cr alloy turn to stable,ξ_eq decrease firstly and then turn to stable.With increasingθ_a, the characteristics of Ti-50.8Ni and Ti-51.1Ni alloy springs evolved from SME to SE, Ti-50.8Ni-0.3Cr alloy spring shows SE all through, and theσ_m of three alloy springs decrease firstly and then increase.A structure design method of a temperature sensitive switch device based on shape memory alloy spring is put forward, and a new idea for the exploiture and design of new product is provided.更多还原