電子背向散射繞射技術於接合製程中之應用

在接合製程中，常會形成寬度從幾十μm至幾mm的銲道與過渡區，此兩區牽涉到熔融與凝固反應導致形成相變態、偏析、介金屬化合物等等，或受到高溫梯度變化的影響，導致晶粒成長或組織改變。傳統上應用TEM或X-ray結構分析上有所不足，在本研究中，透過新發展的電子背向散射繞射技術(Electron Backscattered Diffraction，EBSD)的相鑑定，探討硬銲與氬銲接合製程之特性，硬銲製程為探討鈦基填料Ti-35Ni-25Nb硬銲商用純鈦(CP-Ti)以及Ti-15V-3Cr-3Al-3Sn(Ti-15-3)兩種常見的鈦基合金，在不同的硬銲溫度與時間下進行銲道顯微組織與結構演化之研究。氬銲製程為探討鍋爐鋼T23/T91(T23填料)、T91/304H(309L填料)、T92/304H(309L填料)、T92/304H(Inco82填料)異質銲接後，在高溫老化實驗後於熱影響區產生之碳遷移行為，進行硬度、顯微組織、相鑑定與晶粒取向之研究。在CP-Ti/Ti-35Ni-25Nb/CP-Ti的研究中，1000℃/600秒條件下，銲道為β-Ti相，過渡區為針狀β-Ti分解成細小的共析α-Ti與Ti2Ni；在1200℃/600秒硬銲條件，銲道區的β-Ti會分解成針狀α-Ti以及殘留β-Ti之共析反應，過渡區的微觀組織為殘留β-Ti、沿著針狀α-Ti基地之羽狀晶界共析反應生成的Ti2Ni與α-Ti。Ti-15-3/Ti-35Ni-25Nb/Ti-15-3的研究中，1000℃/3600秒條件下，銲道區為共晶反應形成的β-Ti與Ti2Ni；在較高溫1200℃/600秒條件下，銲道觀察到β-Ti，無Ti2Ni。在T23/T91(T23填料)異質銲接在老化十萬小時後結果，在T23銲道與T91熱影響區之間形成脫碳區；T91/304H(309L填料)與T92/304H(309L填料) 異質銲接在老化二十萬小時後結果，在309L銲道與T91熱影響區之間、309L銲道與T92熱影響區之間形成脫碳區；T92/304H(Inco82填料) 異質銲接在老化二十萬小時後結果，在Inco82銲道與T92熱影響區之間無形成脫碳區，僅觀察到晶粒粗大，顯示Inco82填料可有效減緩碳遷移的發生；應用電子背向散射繞射技術可鑑定上述異質銲接材料之晶體結構與晶粒取向。研究結果顯示，應用電子背向散射繞射技術鑑定幾十μm至幾mm之寬度區域相演變與鑑定結構是較TEM或X-ray方便與快速之方法。

關鍵字

電子背向散射繞射；鈦基填料；鈦基合金；硬銲；介金屬化合物；鍋爐鋼；碳遷移

並列摘要

The joining processes often form dozens 10 μm to several mm width of brazing zone (BZ) and transition zone (TZ), which involve melting and solidification reactions leading to phase transformation, segregation, intermetallic compounds, etc., or subjected to high temperature gradient effect resulting in grain growth or microstructure changes. Traditionally, there are some shortcomings in the application of TEM or X-ray structural analysis. In this study, we adopt the phase identification of the newly developed Electron Backscattered Diffraction (EBSD) technology and discuss the property of brazing and TIG. The study are the BZ/TZ microstructure and intermetallic compounds evolution of Ti-35Ni-25Nb / CP-Ti and Ti-35Ni-25Nb /Ti-15V-3Cr-3Al-3Sn (Ti-15-3) at different brazing temperatures and times and the HAZ microstructure, phase and grain orientation property of carbon migration T23/T91(T23 filler)、T91/304H(309L filler)、T92/304H(309L filler)、T92/304H(Inco82 filler) after different aging time. In the study of CP-Ti/Ti-35Ni-25Nb/CP-Ti, the BZ is β-Ti phase, and the TZ is acicular β-Ti decomposed into fine eutectoid α-Ti and Ti2Ni at 1000℃/600 secs. At 1200℃/ 600 secs brazing conditions, β-Ti in the BZ will decompose into acicular α-Ti and is retained β-Ti via eutectoid reaction. The microstructure of TZ contains retained β-Ti and eutectoid of Ti2Ni and α-Ti along lath boundaries of acicular α-Ti matrix. In the study of Ti-15-3/Ti-35Ni-25Nb/Ti-15-3, the BZ was formed by eutectic reaction of β-Ti and Ti2Ni at 1000℃/3600 secs. At 1200℃/600 secs condition, the BZ was observed β-Ti, no Ti2Ni, and the TZ was β-Ti. In the T23/T91(T23 filler) part, after PWHT and simulated aging test for 100,000 hours, the continuous and coarse decarburization zone forms at the interface of T23 weldment and T91 HAZ. In the T91/304H(309L filler) and T92/304H(309L filler) part, after PWHT and simulated aging test for 200,000 hours, the continuous decarburization zone forms at the interface of 309L weldment and T91 HAZ, 309L weldment and T92 HAZ . In the T92/304H(Inco82 filler) part, after PWHT and simulated aging test for 200,000 hours, the continuous and coarse decarburization zone does’nt forms at the interface of Inco82 weldment and T92 HAZ but shows coarse grains. Inco82 filler can effectively slow the occurrence of carbon migration. EBSD technique can be used to identify the crystal structure and grain orientation of the above DMW materials. The results show that the application of electron backscatter diffraction technology to identify the phase evolution and identification structure of the tens μm – several mm width region is a convenient and rapid method compared with TEM or X-ray.