晶粒細化對TiNi及TiNiCu形狀記憶合金相變態行為影響之研究

Abstract

本研究針對40%冷輥壓Ti50Ni40Cu10合金、Ti51Ni49 melt spinning薄帶及快速凝固鑄造Ti50Ni40Cu10合金進行再結晶退火處理，探討晶粒細化後退火對其相變態行為之影響。研究結果可知，短時間之退火主要用於冷加工殘留應力、缺陷及熱應力之消除；長時間者主要用於晶粒之回復、再結晶及晶粒成長。冷輥壓加工40%之Ti50Ni40Cu10合金經退火處理後，其tanδ極大值皆能超過0.04，符合高制振能合金之要求，其中以 650oC×72hrs之試片為最大。Ti51Ni49 melt spinning薄帶經適當退火處理後會產生多階相變態，其成因和薄帶中同時存在大、小晶粒有關，而退火處理後大晶粒之成長有限，主要為小晶粒之成長。40%冷輥壓及快速凝固鑄造Ti50Ni40Cu10合金之晶粒成長指數隨退火溫度增加而增加，並符合Arrhenius熱活化原子擴散模式，其晶粒成長活化能分別為306.47kJ/mol及1653.4kJ/mol。由本研究結果可知，退火條件對相變態行為影響之主要參數為溫度。

Effects of grain size on transformation behavior and mechanical property of (1) Ti50Ni40Cu10 SMA thin plates with 40% cold rolling, (2) Ti51Ni49 SMA melt-spun ribbons and (3) Ti50Ni40Cu10 SMA rapid solidificated rods with recrystallization annealing are studied. When the annealing time is short, thermal energy contributes to release the residual stress and to eliminate the lattice defects. On the other hand, thermal energy contributes to recovery, recrystallization and grain growth when the annealing time is long. DMA test indicates that 40% cold-rolled Ti50Ni40Cu10 plates have high damping capacity (tanδ>0.04), especially for the plate annealed at 650oC×72hrs. Because of the coexistence of different size grains, Ti51Ni49 melt spinning ribbons reveal multiple martensitic transformation steps. During the annealing small grains show obviously growth but large ones don’t. Both 40% cold-rolled thin plates and rapid solidificated rods have the same property, i.e. their grain growth exponents increase with the increasing annealing temperature and they are consistent with Arrhenius diffusion model having the grain growth activation energies 306.47kJ/mol and 1653.4kJ/mol, respectively. According to this study, the major parameter affecting transformation behavior is the annealing temperature.