Quantitative Research on the Role of Large Precipitates in V-Ti Micro-Alloyed Steel during Dynamic Transformation

doi:10.1007/s40195-014-0170-z

Abstract

Abstract:

To research the effect of large precipitates (size>0.2μm) on strain-induced dynamic transformation, the variation of V contents in large precipitates has been investigated quantitatively in two V-Ti micro-alloyed steels. The results showed that high N content promoted V precipitation on the surface of Ti large precipitates rapidly. Subsequently, large precipitates containing V induced the formation of intragranular ferrite, which accelerated the dynamic transformation process remarkably, promoted the occurrence of continuous dynamic recrystallization of ferrite and improved the refinement effect.

Key words: Transformation, Precipitates, Intragranular ferrite, Recrystallization, EBSD

Da-Yong Wu, Fu-Ren Xiao, Lai-Lei Wu, Ming-Yu Sun, Bo Liao. Quantitative Research on the Role of Large Precipitates in V-Ti Micro-Alloyed Steel during Dynamic Transformation[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(1): 77-82.

Figures/Tables 8

Table 1 Chemical compositions of the two tested steels (wt%)

Steel	C	Si	Mn	P	S	Ti	V	N	Fe
A	0.084	0.66	1.28	0.0065	0.0033	0.020	0.088	0.0051	Bal.
B	0.086	0.66	1.4	0.0065	0.0030	0.020	0.053	0.015	Bal.

Fig. 1 Optical micrographs of steels A and B deformed at 870 °C under different strains: a steel A, ε = 0.22; b steel A, ε = 0.60; c steel B, ε = 0.22; d steel B, ε = 0.60

Fig. 2 The evolution of ferrite fraction (f α ) with the strain for the tested steels

Fig. 3 SEM image a, EDS analysis result b of a large precipitate obtained in steel B under strain of 0.6

Fig. 4 TEM image a, SADP b of a large precipitate obtained in steel B under strain of 0.6

Fig. 5 SEM image a, EDS analysis result b of a large precipitate obtained in steel B under strain of 0.6

Fig. 6 Proportion of V in the large precipitates of the total content measured by ICP-AES a, the mean ferrite sizes b of the steels A and B under different strains

Fig. 7 Boundary misorientation maps and distribution misorientation angles between adjacent ferrite grains for steel B under the strains of 0.91 a, b, 1.20 c, d

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