Abstract
本論文的第一個重點是以複合粉末製程製作Ni3Al介金屬化合物及其複合材成品，實驗結果證明以無電鍍鎳的方法在純鋁粉及純鎳粉表層析鍍一層鎳硼合金層，並以此複合粉末作為製程的起始原料，可以達到B元素均勻分佈的目的，得到機械性質良好的成品；同時無電鍍鎳硼的方式可以改善Ni3Al基材與α-Al2O3強化材之間的界面強度，而α-Al2O3顆粒的添加可以有效地增加Ni3Al耐磨耗性；此外也發現不同比重的粉末在作無電鍍鎳時，可以相同粒子沉降速率作為選擇適當粒度的依據，以減少後續的混合手續。控制反應熱可以達到控制反應產物的目的，是本論文中重要的發現，也就是控制鎳鋁初期反應燒結過程所能達到的最高溫度，可以改變反應產物，若控制反應產物為Ni 2Al3,Ni與極少量Ni3Al的混合物，後續的加工與緻密化才得以順利達成。本論文並藉一系列的XRD與微結構分析，提出純鎳純鋁金屬隨溫度上昇反應形成Ni3Al反應之分段過程；同時發現暫態液相是製程中生成孔洞最主要原因。本論文另一個重點是以多段式燒結方法製作Ni3Al成品，以一系列微觀結構的觀察與機械性質的量測，探討其製程的可行性、反應機構以及微結構與機械性質間的關係。實驗結果證明多段式燒結配合熱機處理可以製作密度高、機械性質良好且尺寸大的Ni3Al鎳鋁介金屬化合物；熱機處理程序可以有效地降低孔隙率達到緻密化的效果；此外也發現只經一次熱機處理的試片，即使熱處理時間長達1200℃ 16小時，仍未能使硼元素順利偏析至晶界；而2次以上的熱機處理可以有效地解決這個問題。此外，本論文也以簡單的模型，建立了Ni3Al燒結試片的抗拉強度與試片孔隙度間的關係式，實驗結果證明此關係式有相當高的可信度。Specimens of boron doped Ni3Al intermetallic compound andintermetallic matrix composite of high density andrelatively large dimension have been synthesized fromcomposite powders through processes of replacing plating andelectroless Ni- B plating on aluminum powder and sinteringthen thermal-mechanical treating. This study demon- stratesthat the uniformly coated Ni-B layer over fine Al or Ni coreparticles has the advantage of uniformly distribution of B,and that strong bond ing at the interface between Ni3Al matrixand re- inforced Al2O3 was achieved. Thus, a maximumstrain about 17, 15 and 9 pct was attained from Ni3Al, Ni3Al/5 vol% Al2O3 and Ni3Al/10 vol% Al2O3 IMC, respectively. Theboron doped Ni3Al specimen fabricated with elemental powdermetallurgy (EPM) method were also studied. This studydemonstrates that the effects of heat diluent on the synthesisof nickel alumi- nides is remarkable, and that the heatdiluent can influence the reacted products of 650℃ reactivesintering. Much brittle NiAl phase was formed withincompacts after 650℃ reactive sintered without heatdiluent, and it will be broken after slightly cold rolling.In contrast, much Ni2Al3 phase was formed within compact after650℃ reac- tive sintered with heat diluent, and it can sus-tain severely cold rolling. The occurrence of transientliquid phase at early stage of sintering is suggested asthe major cause of pores in final product. The multi- pass ofthermal-mechanical treatment (TMT) is sig- nificantlybeneficial to eliminate the pores in material as well as tothe mechanical be haviors. The best elongation of TMTtreated EPM specimens could reach 19%. The relationshipbetween UTS and amounts of porosity in EPM specimens withvarious conditions was also established.