Ti50Ni50-XPdX ( X=20∼30 at％)高溫形狀記憶合金中 Cu取代Ni之研究

Abstract

本研究主要是在Ti50Ni50-xPdx(x：20 ~ 30 at％)合金系統中添加Cu 取代Ni 後，觀察成分之改變對其相變態溫度、相變態潛熱之影響。並 於室溫冷軋延，再經退火等製程，觀察退火對Ti50(Ni, Cu)50-xPdx 合金相 變態行為之影響， 及其顯微結構的改變。由實驗結果可知， Ti50(Ni25-yCuy)Pd25 及Ti50(Ni30-zCuz)Pd20 系列合金，均為ㄧ皆相變態B2 ←→B19，且變態溫度及變態潛熱均會隨Cu 取代Ni 量的增加而上升。 Ti50(Ni15Cu15)Pd20 與Ti50(Ni15Cu10)Pd25 合金，分別經冷軋延加工30%及 28%後於650℃退火，會有析出物的產生，而壓抑B2←→B19 變態，且 析出物隨退火時間的增加而粗化，退火120 小時後，析出物大小約為1 μm，其成份與基質相較下Ti、Ni 含量較少，而Cu、Pd 含量較多。 Ti50(Ni25Cu5)Pd20 合金經冷軋延加工25%後於500℃退火，會有析出物的 產生，但因析出物極微小，無法在SEM 中觀察之。由SME 測試結果得 知：Ti50(Ni15Cu10)Pd25 及Ti50(Ni25Cu5)Pd20 合金試片經冷軋延加工後，再 經800℃及650℃高溫退火後，其SME 的表現比900℃熱軋延者要好， 而Ti50(Ni25Cu5)Pd20 合金經500℃退火10 分鐘的SME 表現為最佳。

Transformation temperature and latent heat of Ti50(Ni, Cu)50-xPdx （x：20 ~ 30 at％）high temperature shape memory alloys（SMAs）are studied. In addition, annealing effect on transformation behavior and microstructure of cold-rolled Ti50(Ni, Cu)50-xPdx SMAs is also studied. Ti50(Ni25-yCuy)Pd25 and Ti50(Ni30-zCuz)Pd20 SMAs both exhibit one-stage B2←→B19 transformation, and their Ms and ΔH increase with increasing the Cu substitution. Severely cold-rolled and 650℃ annealed Ti50(Ni15Cu15)Pd20 and Ti50(Ni15Cu10)Pd25 alloys induce precipitates in the matrix. The precipitates increase their size with prolonging annealing time and deteriorates the alloys’ shape memory effec（t SME）. The composition of the precipitates is identified as (Ti,Cu)2(Pd,Ni) by EDX test. The precipitates of 25％cold-rolled and 500℃annealed Ti50(Ni25Cu5)Pd20 are too small to be observed in SEM. However, Ti50(Ni15Cu10)Pd25 and Ti50(Ni25Cu5)Pd20 SMAs cold-rolled and annealed at 650℃ and 800℃, respectively, show no precipitate and good SME. Among all Ti50(Ni, Cu)50-xPdx SMAs, Ti50(Ni25Cu5)Pd20 SMA with 25％ cold rolling and 500℃×10min annealing 10 mins exhibits the best SME.