Development of Texture, Microstructure, and Grain Boundary Character Distribution in a High-Strength Boron-Added Interstitial-Free Steel after Severe Cold Rolling and Annealing

Abstract

A high-strength boron-added interstitial-free (IF) steel was subjected to cold rolling by 90 and 98 pct. Both these materials were subjected to annealing at 650°C and 700°C for various lengths of time. An in-depth thorough study has been carried out on the evolution of texture, microstructure, and grain boundary character distribution (GBCD), as a function of cold rolling and annealing. Formation of strain-free nanosize grains at few places has been observed in the severely cold-rolled (98 pct) steel. Ultrafine grains formed in this material at the early stages of annealing. The deformation texture sharpened and the high-angle grain boundary (HAGB) density increased with increasing amount of cold rolling. The intensity of a-fiber components increased at the early stages of annealing, while the c-fiber components were found to predominate at the later stages. Selective growth of grains having orientations {111}h123i and {554}h225i occurred in the 98 pct cold-rolled and annealed material. The textural and microstructural results indicate that in these materials the recrystallization process may be of a continuous type.

Liquid-phase boriding of high-chromium steel

“…Максимальная концентрация бора в используемых в настоящее время сталях не превышает 1,8 % (по массе) (сталь марки ЧС82), что обусловлено низкой пластичностью легированного бором материала, вызванной грубой формой бори-дов [2,3]. Измельчение структуры стали и сфероидизацию боридов осуществляют путем термомеханической обработки стали [4] и дополнительным легированием [5 - 9]. Цитируемые методы и подходы основаны на объемном модифицировании структуры и свойств стали.…”

Boron-Containing Steel Structure and Properties at Room and Elevated Temperature

“…4c, d). In contrast to the steel subjected to rapid plastic deformation, within which diffusion processes of spheroidization and coagulation are significantly accelerated [5,6], in our case a temperature below 600°C is too low for active occurrence of these processes [9,10], the increase in average particle size with an increase in temperature is insignificant (Fig. 5), and it is mainly due to the dissolution of the finest particles formed as a result of eutectic crystallization, and also precipitated during slow steel cooling after forging.…”

“…In order to reduce embrittlement caused by the coarse shape of boride, it is necessary to perform steel deformation and heat treatment. Research has shown that the intensity of rapid plastic deformation (90-98%) followed by annealing in the range 600-700°C leads to the formation of an ultrafine grain structure and boride spheroidization [5,6], and this has a favorable effect on steel ductility. Additional alloying with titanium also improves ductility [7], and this is due to forming titanium boride (TiB 2 ) instead of iron and chromium boride (Fe, Cr) 2 B due to the greater thermodynamic stability of the first [8,9].…”