Fe-15Ni-0.6C合金马氏体浮凸及相变新机制

对预先抛光的Fe-15Ni-0.6C合金试样进行真空热处理,随后用Nano First-1000型扫描隧道显微镜和QUANTA-400型环境扫描电镜对未经浸蚀的试样进行观察分析,发现,Fe-15Ni-0.6C合金马氏体片的浮凸为帐篷形（∧型）,浮凸最高高度为43~96 nm。分析认为,马氏体表面浮凸是由于过冷奥氏体转变为马氏体时比体积增大、体积膨胀造成的,而非切变所致。对浮凸高度进行了理论计算,结果表明,马氏体线膨胀量比实测的浮凸高度大,计算的浮凸平均高度为162 nm,是膨胀过程受阻所致。浮凸非N形,是帐篷形,不具备切变特征,马氏体的切变机制缺乏实验依据,也与实际不符。提出了马氏体相变新机制。

Martensitic Surface Relief and New Martensite Transformation Mechanism for Fe-15Ni-0.6C Alloy

The pre-polished specimens of Fe-15Ni-0.6C alloy were vacuum hot processed,and subsequently were observed and analyzed by means of Nano First-1000 scanning tunneling microscope（STM） and QUANTA-400 environment scanning electron microscope（SEM） under unetched condition.The results show that the martensite surface relief of Fe-15Ni-0.6C alloy is tent-like（∧-shaped）and its maximum height is 43 to 96 nm.The formation of martensitic surface relief is considered to arise from the increase in specific volume and thereby volume expansion instead of the shear.Theoretical calculation of surface relief height shows that the linear expansion amount of martensite is in excess of practically measured relief height and that the calculated average relief height is 162 nm,which is traced to the expansion process being blocked.The relief is not N-shaped but tent-like,and consequently can not be characterized by the shear.The shear mechanism of martensite transformation is lacking in experimental basis and inconsistent with actual situation.