Microstructure of ausformed lath martensite in 18%Ni maraging steel

Abstract
The microstructure of ausformed lath martensite in 18%Ni maraging steel was studied by analyzing electron backscatter diffraction pattern obtained by scanning electron microscopy and Kikuchi diffraction pattern obtained by transmission electron microscopy. In non-ausformed lath martensite structure, blocks and packets are clearly observed by optical microscopy. By ausforming of 60% at 773 K, packet and block widths of lath martensite decrease whereas the packet is elongated along rolling direction. A packet of ausformedlath martensite contains some laths which belong to a crystallographically different packet. The dislocation density in ausformed lath martensite is higher than that in conventional lath martensite. It is concluded that ausforming refines the effective grain size and increases the dislocation density in lath martensite structure.