ABSTRACT

In general, the formation of martensite in the metastable austenite grains in steels during nanoindentation investigations is believed to be induced by strain as the plastic deformation of austenite takes place prior to the martensitic transformation. However, it is not clear whether the formation of martensite occurs without the prior initiation of plasticity (stress-induced martensitic transformation) during nanoindentation measurement. The present work demonstrates that the martensitic transformation can be triggered during elastic deformation of austenite under an ultralow load when the indenter is close to the annealing twin boundaries. The indentation pressure interacts with the martensite transformation strain, providing the mechanical interaction energy to overcome the nucleation barrier of the martensite embryo. The present work suggests that the annealing twin boundaries can also serve as the nucleation sites of martensite and the stress-induced martensitic transformation is possible during nanoindentation investigation.

摘要

通常，在纳米压痕研究期间，钢中亚稳态奥氏体晶粒中马氏体的形成被认为是由应变引起的，因为奥氏体的塑性变形发生在马氏体转变之前。然而，尚不清楚在纳米压痕测量过程中是否在没有事先引发塑性（应力诱导马氏体转变）的情况下发生马氏体的形成。目前的工作表明，当压头接近退火孪晶边界时，在超低载荷下奥氏体的弹性变形过程中可以触发马氏体转变。压痕压力与马氏体转变应变相互作用，提供机械相互作用能以克服马氏体胚的形核势垒。