本文从多方面研究观察再次证实贝氏体铁素体相变基元的存在，相变基元为切变相变基元，并提出其形态示意图。在Ｆｅ－Ｃ合金中，本文观察到正三角型、交叉型、“Ｎ”型和蝴蝶型类马氏体形貌贝氏体。在交叉型贝氏体中，发现基元相对滑移的、相互脱节的、形成“束腰”的和互换生长取向的交叉型贝氏体，交叉效应直接体现于相变基元的活动行为，相应提出其活动行为示意图。导致交叉的应力场是切变相变剪切应力集中应力场，贝氏体交叉的形成是切变应力－应变诱发贝氏体转变的结果。在应变诱发贝氏体转变时，相变驱动力的补偿与奥氏体所发生的真实应变的平方成正比，两贝氏体铁素体碰撞非常猛烈，承认其形成方式为切变型可得到说明。
The occurrence of bainitic ferrite transformation units, namely, shear transformation units,in Fe-C alloys was repeatedly confirmed by various observations,and a sketch illustrating their morphology was given.Some martensite-like bainites,such as regular triangular, crossed,"N"- and butterfly-type,were observed in the alloys. The crossed bainite may be further divided into 4 types,i.e.,units of relative glide disjunction,"wasp- waist"formation and exchange growing orientation.The crossing effect reflects directly on movement of bainite units during transformation.The induced crossed stress field is one of the shear stress concentration under shear transformation.The formation of bainite crossing is caused in the shear stress-strain induced bainitic transformation.The compensation value for the driving force of transformation is proportional to the square of true strain of austenite.The extraordinal violence of impingement brought about by the growing bainite plates can only be explained through shear mechanism of bainitic transformation.Correspondent: YU Degang, professor,(Departrnent of Materials Science, Shanghai Jiaotong University,Shanghai 200030)
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