热处理和循环应变对TiNiZr合金形状记忆行为的影响

Effect of heat treatment and cyclic strain on shape memory behaviors of TiNiZr alloy

摘要:

利用拉伸实验、光学显微镜和透射电镜研究了退火工艺、时效工艺和循环应变对Ti-50.8Ni-0.1Zr合金形状记忆行为的影响。350~400 ℃和600~700 ℃退火态合金呈超弹性(SE),450~550 ℃退火态合金呈形状记忆效应(SME)；300 ℃/(1~50 h)和400 ℃/1 h时效态合金呈SE,400 ℃/(5~50 h)和500 ℃/(1~50 h)时效态合金呈SME。随退火温度升高,合金应力应变曲线平台应力σ_M先降低后升高,最小值200MPa在500 ℃退火后取得；残余应变ε_R先升高后降低,最大值2.64%在500 ℃退火后取得。随时效时间延长,300 ℃时效态合金的σ_M降低,ε_R始终较小；400 ℃和500 ℃时效态合金的σ_M降低,ε_R先升高后趋于稳定。随循环次数增加,呈SE的合金由部分非线性SE转变为完全非线性SE,且σ_M和能耗△W先降低后趋于稳定；呈SME的合金的σ_M和△W先降低后趋于稳定。

Abstract:

The effects of annealing processes, aging processes and cyclic strain on shape memory behaviors of Ti-50.8Ni-0.1Zr alloy were investigated by tensile test, optical microscopy and TEM. The alloys annealed at 350~400 ℃ and 600~700 ℃ present superelasticity (SE), the alloys annealed at 450~550 ℃ present shape memory effect (SME), the alloys aged at 300 ℃ for 1~50 h and at 400 ℃ for 1 h present SE, and the alloys aged at 400 ℃ for 5~50 h and 500 ℃ for 1~50 h present SME. With increasing annealing temperature, the platform stress (σM) of the stress-strain curve in the alloy decreases firstly and then increases, and the minimum 200 MPa obtained in the alloy annealed at 500 ℃; the residual strain (εR) increases firstly and then decreases, and the maximum 2.64% obtained in the alloy annealed at 500 ℃. With increasing aging time, the σM decreases, and the εR is small in the alloy aged at 300 ℃; the σM decreases, and the εR increases firstly and then tends to stable in the alloy aged at 400 ℃ and 500 ℃. With increasing stress-strain cycle number, the superelasticity type alloy transforms from incompletely nonlinear superelasticity to completely nonlinear superelasticity, and the σM and energy dissipation (△W) decrease firstly and then tend to stable; the σM and △W decrease firstly and then tend to stable in shape memory effect type alloy.