Precipitation behavior and mechanical properties of a hot rolled Ti-bearing dual phase steel

Abstract

We have studied here the microstructure, precipitate evolution and mechanical properties in a Fe-Mn-Cr-Ti dual phase steel processed by thermo-mechanical control processing. When the deformed austenite was treated in the temperature range of 640-760 ºC, the microstructure consisted of ferrite and 7-80% martensite. Both random and interphase precipitation of nanoscale TiC particles occurred in the ferrite matrix. With decrease in temperature, the average size of precipitates was reduced from 5.4 nm to 2.2 nm, and the morphology of interphase precipitation was altered from curved to planar because of the change in the mechanism of TiC interphase precipitation. Hot rolling inhibited interphase precipitation but promoted precipitation on dislocations. Given that the ferrite matrix was significantly strengthened by nanoscale TiC particles, the hardness difference between the ferrite matrix and martensite was significantly decreased, and the strength of hot rolled Ti-bearing dual phase steels was less dependent on the martensite content compared to the conventional dual phase steels. The strength of hot rolled Ti-bearing dual phase steels was derived from a number of strengthening mechanisms, namely phase transformation, precipitation and grain refinement strengthening.

Effect of Processing Parameters on Interphase Precipitation and Mechanical Properties in Novel CrVNb Microalloyed Steel

“…Similarly, ~50% reduction in intersheet spacing of VC was noted after deformation of austenite prior to phase transformation [36]. In 0.06C-0.1Ti-0.5Cr (wt.%; hereafter all compositions are given in wt.%) steel, a decrease in holding temperature from 720 to 640 • C resulted in more planar rows of TiC, their size and intersheet spacing decreased, number density increased, and the steel hardness increased [37]. In another Ti-microalloyed steel containing 0.06C-0.1Ti-0.2Mo, a decrease in temperature from 720 to 630 • C also resulted in the sheet spacing decreasing and strength increasing, although various morphologies (irregular and regular intersheet spacing, and curved or straight row lines) of interphase precipitates were observed in different grains [24].…”

Effect of cooling temperature on microstructure and mechanical properties of Ti microalloyed steel

“…Synchronously, if the slow cooling temperature of the cooled steel plate is lower, the amount of dislocations will retain greater. These large amounts of dislocations provide a lower energy nucleation location for the precipitated phase, which further increases the nucleation rate of the precipitated phase [7] . In addition, the lower the slow cooling temperature of the steel plate is, the smaller the range of atomic diffusion is, and the smaller the number of atoms available for the formation and growth of the precipitated phase is.…”

Pengaruh Kecepatan Pendinginan Baja Fasa Ganda Fe-Ni hasil Tempa Panas terhadap Struktur Mikro dan Nilai Kekerasan

“…Umumnya, baja fasa ganda terdiri dari fasa feritmartensit dengan komposisi tertentu. Beberapa penelitian menyatakan, dengan membatasi rasio ferit-martensit pada rentang 60:40 atau 70:30 dapat mempertahankan sifat keuletan [13,14]. Namun, terdapat pula penelitian yang menyatakan bahwa kandungan martensit hingga mencapai 50% mampu menghasilkan performa yang baik [12].…”