Fe-0.7C-13Cr合金鋼透鏡狀麻田散鐵之顯微結構及晶體結構分析

Crystallographic Analysis and Microstructure Characterization of Lenticular Martensite in Fe-0.7C-13Cr Steel

賴世雯(Shih-Wen Lai)

指導教授 ： 楊哲人

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201703138

摘要

本研究是以Fe-0.7C-13Cr合金鋼所生成的透鏡狀麻田散鐵為研究對象，分析其顯微結構與晶體結構。施以1200℃下72小時的熱處理，將碳化物完全溶回基地中，再施以不同的深冷溫度，得到不同的麻田散鐵相比例，來進行方位關係和變體選擇的研究。經過均質化和深冷處理後，此合金成分下會生成透鏡狀麻田散鐵，利用穿透式電子顯微鏡(TEM)觀察到透鏡狀麻田散鐵內部分成三個區域，分別為中脊區(midrib)、雙晶擴展區(twinned region)和非雙晶區(untwinned region)。利用電子背向散射繞射(EBSD)得知此透鏡狀麻田散鐵和沃斯田鐵之間為Kurdjumov-Sachs (K-S)方位關係，並且可以利用多個不同的麻田散鐵variant中midrib的方位可以計算出晶癖面(habit plane)的方位。透鏡狀麻田散鐵生長初期會由任意一個的plate group和其雙晶主導，其他的plate group可能佔據沃斯田鐵晶界附近自成一個系統的plate group或是在殘留沃斯田鐵區域中生長。麻田散鐵variant pair如：V1-V6、V1-V16、V1-V17 variant pair會展現特定形貌：V1-V16會從M/A界面生長出來，V1-V6和V1-V17麻田散鐵大多在端點接觸，夾角會因切面和形貌不同而有變化。
最後，利用穿透式電子顯微鏡(TEM)和穿透菊池繞射(TKD)的結果，說明在電子背向散射繞射(EBSD)中觀察到的一支透鏡狀麻田散鐵內基地和雙晶的variant在發生互換，還有midrib兩側分別為麻田散鐵基地的variant和雙晶的variant，這種非典型的透鏡狀麻田散鐵是確實存在的，但其生成機制仍尚待釐清。

關鍵字

透鏡狀麻田散鐵 ； 變體選擇 ； 變體對 ； 晶癖面 ； plate group ； 晶癖面 ； EBSD ； TKD

並列摘要

The crystallography and microstructure of lenticular martensite in Fe-0.7C-13r stainless steel has been studied by EBSD, TKD, and TEM in this research. In Fe-0.7C-13r stainless steel, after austenization treatment at temperatures 1200°C for three days, austenite was stable at room temperature and would transform to lenticular martensite after subzero treatment. That lenticular martensite consisting of three regions: the midrib, the twinned region, and the untwinned region was observed by TEM. EBSD analysis shows that the orientation relationship between austenite and martensite is Kurdjumov-Sachs orientation relationship and the traces of midrib of many martensite variants can be used to calculate the normal of habit plane. At initial stage of the formation of lenticular martensite, one random plate group and twin variants of this plate group will be dominant. Other plate groups can only form in retained austenite and the area near grain boundaries. Specific variant selections of lenticular martensite show particular morphologies. Generally, V1-V16 coupling mostly forms from M/A interface while V1-V6 and V1-V17 coupling usually form from the endpoint of lenticular martensite. In this case, the angle between V1 and V6 is about 38° while the angle between V1 and V17 is about 72°; however, different cross-section and morphology will make the angles change.
During analyzing of EBSD results of lenticular martensite, some peculiar microstructures of lenticular martensite were observed. Because of the large interaction volume and the limited resolution of EBSD, TKD and TEM were used to confirm that those microstructures were actual microstructures rather than misleading results due to EBSD limitations. In Fe-0.7C-13r stainless steel, those microstructures could be considered atypical lenticular martensite but the mechanism is not clear.

並列關鍵字

lenticular martensite ； variant selection ； variant pair ； plate group ； habit plane ； EBSD ； TKD

參考文獻

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