The transformation behavior and microstructure in a medium-carbon bainitic steel were investigated by combination of metallography and dilatometry. The fine micro-structural units of carbide-free bainite in non-ausformed and ausformed materials were measured by a transmission electron microscope. Mechanical stabilization of austenite in deformed material and its effect on property were analyzed by nanoindentation and tensile tests. Ausforming with a strain of 0.2 at 573 K can not only accelerate bainite transformation, but also improve the comprehensive properties. The strength and ductility of nanostructured bainitic steel can be simultaneously enhanced by ausforming, which should be attributed to the refinement of bainite and the enhanced volume fraction of retained austenite. Compared to the non-deformed material, the mechanical stabilization of austenite can be optimized by ausforming, resulting in good transformation-induced plasticity effects. Also a very important advantage was that, the bainite transformation time could be minimized into practical scale by prior ausforming compared to traditional low-temperature austempering.

通过金相学和膨胀学研究了中碳贝氏体钢的相变行为和组织。用透射电子显微镜测量了未锻压和奥氏体材料中无碳化物贝氏体的细微结构单元。通过纳米压痕和拉伸试验分析了奥氏体在变形材料中的机械稳定性及其对性能的影响。在573 K处以0.2应变进行奥氏体成形不仅可以加速贝氏体转变，而且可以改善综合性能。可以通过奥氏体化同时提高纳米贝氏体钢的强度和延展性，这应归因于贝氏体的细化和残余奥氏体体积分数的增加。与未变形的材料相比，奥氏体的机械稳定性可以通过奥氏体进行优化，从而产生良好的相变诱导塑性效应。还有一个非常重要的优点是，与传统的低温奥氏体淬火相比，通过事先的奥氏体成形可以将贝氏体的转变时间最小化到实际规模。