Study of Microstructural Evolution of X4CrNiSiTi14-7 During Thermal Aging

Abstract

Microstructural evolution during aging treatment in a high tensile precipitation hardening stainless steel (X4CrNiSiTi14-7) has been investigated. Matrix consists of martensitic structure and the combined addition of Si and Ti causes an intermetallic phase type Ni16Ti6Si7 that precipitates with-in grains and enhance precipitation strengthening. This material shows a good combination of high strength and ductility.Light-Optical microscopy, electron back scattered diffraction, transmission electron microscopy and X-ray diffraction analysis have been used to study the microstructural evolution during aging. It has been found that precipitations of various kinds are taking place during aging treatments including nm-scaled G-phase and various carbides. Higher aging temperatures lead to reverse transformation of martensite to austenite.

Localized ageing in the heat affected zone of welded X5CrNiCuNbl6-4 and X4CrNiSiTi14-7 sheets

“…This behavior can be explained on the basis of precipitation hardening. This high hardness of basematerial is due to the presence of fine G-phase precipitates [5,6] and shown in Figure 17. During welding the heat was sufficient to cause melting in the centre of weld zone.…”

“…The second alloy type that is used in this study is X4CrNiSiTi14-7, which is a high tensile strength precipitation hardening stainless steel with martensitic microstructure. This alloy is hardened by G-phase precipitation [5,6].…”