- 學位論文
鎳-18鉻-15鐵-5鈮-3.5鉬-3鈷-1.4鈦-1鋁合金相變化
Phase Transformation on Ni-18Cr-15Fe-5Nb-3.5Mo-3Co-1.4Ti-1Al Alloy
摘要
本研究主要探討，鎳-18鉻-15鐵-5鈮-3.5鉬-3鈷-1.4鈦-1鋁合金之相變化，結果如下： 鍛件經固溶熱處理1200℃/1小時的條件，為沃斯田鐵γ基地，晶格常數為a=0.355nm。經時效溫度在500℃、600℃之低溫240小時長時效後，無任何析出物在晶粒與晶粒邊界析出。 經由650℃、700℃、750℃、780℃時效溫度時，可發現球狀之L’12結構κ相在沃斯田鐵基地析出，晶格常數為a=0.358nm，其析出物與基地間保持良好之整合性(coherency)。時效830℃、880℃，可發現長條狀之L’12結構κ相，晶格常數為a=0.363nm，且析出物存在界面差排，與基地形成半整合性(semi-coherency)析出。經由時效880℃/24小時，可發現δ相在晶粒邊界開始析出，晶格常數為a=0.513nm、b=0.426 nm、c=0.455 nm，且δ相存在溫度較IN718高。 在二階段式時效方面，經由750℃ /16小時+650℃/8小時之二階段式時效時，其硬度值為Hv=446.7，為二階段式時效硬度之最佳值，所以本實驗以 750℃/16小時+650℃/8小時之二階段式時效條件定為此合金能獲得最佳硬度值之熱處理條件。
並列摘要
The aim of this paper is to discuss the phase on Ni-18Cr-15Fe-5Nb-3.5Mo-3Co-1.4Ti-1Al alloy, based on the present study, some results are described ： During the solution treatment 1200℃/1h, microstructure of the as-forged alloy was austenite γ-phase with lattice parameters a=0.355nm. After the 500℃ and 600℃/240h long aging processed, found no precipitate in the grain and grain boundaries precipitates. During the 650℃、700℃、750℃ and 780℃ aging processed, found the L'12 structure of spherical κ-phase were formed within the matrix coherently, the lattice parameters a= 0.358nm. During 830℃ and 880℃ aging processed, found the L'12 structure of the dark stripκ-phase, the lattice parameters a= 0.363nm, and the precipitate phase there are dislocations, the base of the formation of semi-coherency precipitation. After 880℃/24h aging processed, the TEM bright field and dark field and SADP was found the δ-phase were formed within the grain boundaries, the lattice parameters a= 0.513nm、b=0.426 nm、c=0.455 nm, and the existence of δ-phase high temperature than IN718. During the 750℃/16h+650℃/8h two steps aging processes, the hardness test value Hv=446.7, this is also the high hardness value by two steps aging processes.