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    Please use this identifier to cite or link to this item: http://ir.lib.ksu.edu.tw/handle/987654321/19758

    Title: TiNiCr
    其他題名: A study of Thermo-mechanical treatment of TiNiCr Ternary Shape Memory Alloys
    Authors: 陳建宏
    homn, chen chan
    Contributors: 謝世?
    Hsieh shin feng
    ???metadata.dc.contributor.other???: 國立高雄應用科技大學模具工程系碩士班
    Keywords: 形狀記憶合金;擬彈性;形狀記憶效應
    shape memroy alloy;Pseudoelastic;shape memory effect
    Date: 2008
    Issue Date: 2013-08-28 14:34:38 (UTC+8)
    Abstract: 本研究針對Ti50Ni50-XCrX(X=0.5, 1.0at.%)合金做熱機處理之研究。對Ti50Ni49.5Cr0.5實施15%、25%、35%之冷加工後以及退火處理,並探討其晶粒細化後退火對TiNiCr三元合金之相變態行為之影響。並探討在添加1.0at.%Cr元素後對TiNiCr合金進行熱機處理(時效處理,熱循環處理)並針對相變態行為、熱焓量之變化進行探討。 Ti50Ni49.5Cr0.5三元系形狀記憶合金在經過不同條件的冷輥延與退火處理會有產生多階段的麻田散體轉換。這些現象的形成是因為沿著在材料厚度不同的晶粒大小所導致的。在光學顯微鏡下顯示出在不同退火條件下其晶粒大小會有所不同。在這些退火條件下,計算出再結晶的活化能為71KJ/mol而比Ti50Ni50合金再結晶的活化能51KJ/mol還要來的大,主要是因為Cr原子的固溶所導致的。實驗結果顯示本合金在冷輥延與500?C 、650?C退火處理後,其晶粒成長係數為0.12,0.15。形狀記憶效應會隨著冷輥延量的增加有所有增加。在Ti50Ni49Cr1.0合金於固溶處理後產生了兩階段之變化(B19’?R?B2)、然而在Cr元素添加使其固溶強化而導致合金基地硬度提高,因此在經過時效400℃×240hr後,M*溫度比固溶強化之M*來的低、此乃因第二相Ti2(Ni,Cr)與基地之間原子的擴散使基地之成份會有所減少而導致變態溫度的稍為下降。且在相同情況下熱循環後其硬度也會比原來的Ti50Ni50還要來得高;主要因合金在熱循環初期會較容易導入差排以及缺陷,使M*與R*溫度會逐漸降低且下幅度會比Ti50Ni50來的大。本合金經熱循環後之強化效應亦遵循著Ms=TO-K△σy,其中K值代表著的強化機構;而添加Cr後,其固溶強化硬度來的比較高,所以其K值較大。本合金也會因添加Cr元素後產生固溶強化,致使K值比Ti50Ni50、Ti51Ni49還要來的大。
    This study investigates the effects of the thermo-mechanical treatment on Ti50Ni49.5Cr0.5 and Ti50Ni49Cr1 ternary shape memory alloys. Ti50Ni49.5Cr0.5 alloy’s plates were cold-rolled at room temperature to15, 25 and 35% reduction in thickness, and then annealed at various temperature, 350?C ~650?C, for different time intervals (10 s ~ 24 hours). Effects of grain size on transformation behavior of this alloy after cold rolling and subsequent annealing are studied. The transformation behaviors and shape memory characteristics of Ti50Ni49Cr1 alloy will also be studied under various aging and thermal-cycling treatment processes.Ti50Ni49.5Cr0.5 ternary shape memory alloy cold-rolled and annealed at specific conditions can exhibit multiple-stage martensitic transformation. This feature may arise from the grain size distribution along the specimen’s thickness direction. Optical microscopic results reveal the size of grains after various annealing conditions. From these results, the activation energy of recrystallization is calculated as 71 KJ/mole, which is larger than that of Ti50Ni50 alloy, 51 KJ/mole, due to the solid solution of Cr atoms. The experimental grain-growth exponents at 500?C and 650?C are 0.12 and 0.15 for cold-rolled specimens, respectively. Shape recovery of cold-rolled alloy increases with increasing the amounts of thickness reduction.The solution-treated Ti50Ni49Cr1 alloy undergoes two-stage B2?R?B19’ martensitic transformation. M*, R* and A* decrease with increasing aging time at 400?C because the Cr atoms diffuse slightly from the Ti2Ni to the B2 matrix. At the same time, M* and A* of this alloy can be more depressed by thermal cycling than those of the Ti50Ni50 alloy. This feature results from the fact that this alloy has a higher inherent hardness due to the solid solution of the Cr atoms. The strengthening effect of thermal-cycling on the M* ( Ms) temperature of this alloy follows the expression Ms=T0 ? K??y, in which K values are affected by different strengthening process. It is found that the higher the inherent hardness of the Ti51Ni49 and Ti50Ni49Cr1alloys, the higher the K values they have.
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