EBSD研究高Mn TRIP钢伪线织构

STUDY ON AXIOTAXY IN HIGH MANGANESE TRIP STEEL BY EBSD

对高Mn TRIP钢两类马氏体相变取向关系及变体选择进行EBSD取向成像分析时,在微区内经常观察到伪线织构,并对其进行了分析.结果表明,各类伪线织构都是相变时界面匹配的表现,可由4种原因引起:奥氏体内产生的ε马氏体中按K-S关系生成的6个α′马氏体变体造成;形变时奥氏体内增加的孪晶内形成的ε马氏体构成:相变时两相对应点阵面力图匹配而造成的EBSD相鉴定过程规律性的误标所致;形变促进不同相的点阵面匹配造成.此外,对伪线织构在极图上的表现进行了分析.

An off-normal fiber like texture,also regarded as the fourth texture,that is named axiotaxy.Axiotaxies concern the preferred grain orientations along the axes in crystallographic coordinate s ystem,rather than the axes in sample coordinate system.They reflect the extent of phase boundary matching during,e.g.,martensitic transformation or thin film deposited on single crystal substrates as well as the selection of variants.The excellent properties of high manganese TRIP steels with a good combination of strength and elongation attract great interest of automobile industry and thus the research on this type of steels is increasing.The reason responsible for the super properties of the steels is mainly due to the presence of two types martensites（α＇- andε-martensite） which can form either thermally during quenching or strain induced.Therefore,the Axiotaxies related with these two types of martensites are more complicated and may show more information.This paper investigated the axiotaxies revealed by EBSD orientation mapping during the study of orientation relationship and variant selection in martensitic transformation of two high manganese TRIP steels with 18%Mn and 22%Mn together with 3%Si and 2%Al.It is shown that the quasi-fiber textures in these steels can be caused in 4 ways.First,they were caused by the 6α＇-martensite variants formed in anε-martensite plate which were generated from an austenitic {111} plane by K S relationship.The center of axiotaxy corresponds to the normal of habit plane {111}_γand this type of axiotaxy was observed only in the pole figures ofα＇-martensite.Secondly,they were due to theε-martensite transformed from austenitic deformation twins,this indicates an important role of twinning in martensitic transformation.Thirdly, they were caused by regularly mis-indexing of phases due to the strain aroused by martensitic transformation, namely,the real axiotaxy existed inα＇- martensite was transferred erroneously into the pole figures ofγ-austenite orε-martensite.Fourthly,they may also be due to the accommodation of lattice planes for low misfits by means of external deformation.All of axiotaxies detected were related with martensitic transformation and the significance of analyzing axiotaxy lies in that it reveals much information about phase boundary match,variant selection or the effects of deformation during quenching or during deformation.