离子研磨对TRIP780钢中残留奥氏体含量和稳定性的影响

Effect of ion milling on retained austenite content and stability in TRIP780 steel

研究了经离子研磨对TRIP780钢中残留奥氏体含量与稳定性的影响。首先利用电解抛光技术对TRIP780钢进行样品制备以去除样品表面的应力层,然后利用离子研磨仪对所得样品进行离子研磨,再借助场发射扫描电镜对TRIP780钢中的残留奥氏体进行形貌观察与分析,利用电子背散射衍射技术(EBSD)对离子研磨前后的TRIP钢中残留奥氏体含量进行定性和定量分析。结果表明,与电解抛光相比,离子研磨技术同样可以很好的去除样品表面应力层,但是对于TRIP780钢,经过离子研磨后样品中残留奥氏体的含量大幅度减少,从原来的10.1%骤降至0.02%。从残留奥氏体的菊池花样可以看出,经离子研磨后的残留奥氏体菊池花样明显变差,甚至模糊不清。经离子研磨后的TRIP780钢中残留奥氏体含量明显下降,同时其相结构确实发生了转变,由原来的面心立方结构转变为体心立方结构(即fcc→bcc),由此表明残留奥氏体在受到离子轰击后极其不稳定,易发生相变,这一点在残留奥氏体的准原位试验中得到了进一步的验证。同时离子研磨诱发了晶格的畸变,导致菊池花样清晰度明显下降,花样分辨率降低。

Effect of ion milling on the content and stability of retained austenite in TRIP780 steel was investigated.Firstly,TRIP780 steel specimens were prepared by electropolishing to remove the stress layer on their surface,then ion milled and the retained austenite in the specimens was examined by field emission scanning electron microscope.The retained austenite content in the TRIP780 steel before and after ion milling was further analyzed qualitatively and quantitatively by electron backscatter diffraction(EBSD).The results show that,compared with electropolishing,the ion milling can also remove the stress layer on the specimen surface,however,the retained austenite content in the TRIP780 steel specimen after ion milling is greatly reduced from the original 10.1%to 0.02%,and the Kikuchi pattern of the retained austenite after ion milling is obviously worse or even blurred.The retained austenite content in the ion-milled TRIP780 steel decreases significantly,and the phase structure changes from the original face-centered cubic to the body-centered cubic(fcc→bcc),thus indicating the retained austenite is extremely unstable after ion bombardment and is prone to phase transformation,which is also verified in the quasi-in-situ experiment of retained austenite.The ion milling induces lattice distortion,resulting in a significant decrease in the clarity and resolution of the Kikuchi pattern.