Dynamic Compression Behavior and Microstructure of a Novel Low-Carbon Quenching-Partitioning-Tempering Steel

doi:10.1007/s40195-014-0083-x

Abstract

Abstract:

A 0.2C-1.5Mn-1.5Si-0.6Cr-0.05Nb (wt%) steel is treated respectively by novel quenching-partitioning-tempering (Q-P-T) process and traditional quenching and tempering (Q&T) process for comparison. X-ray diffraction analysis indicates that Q-P-T steel has about 10% retained austenite, but Q&T steel hardly has one. With the increase of compression strain rate from 7 × 10² to 5 × 10³ s^-1, the flow stress of Q-P-T steel increases, which demonstrates the positive strain rate effect, but does not exist in Q&T steel. The characterization of scanning electron microscopy indicates that a large number of long, straight martensite laths in Q-P-T steel will bend or be destroyed by large compressive strain of 35% at 5 × 10³ s^-1. However, relative small compressive strain of about 5% at 7 × 10² s^-1 almost does not have any effect on the original lath morphology. The characterization of transmission electron microscopy further reveals the origin of the positive strain rate effect and the microstructural evolution during dynamic compressive deformation.

Key words: Quenching-partitioning-tempering (Q-P-T) steel, Retained austenite, Strain rate effect, Microstructural characterization

Qingguo Hao, Ying Wang, Xiaoshuai Jia, Xunwei Zuo, Nailu Chen, Yonghua Rong. Dynamic Compression Behavior and Microstructure of a Novel Low-Carbon Quenching-Partitioning-Tempering Steel[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(3): 444-451.

Figures/Tables 10

Table 1 Chemical compositions of the experimental steel (wt%)

C	Mn	Si	Cr	Nb	P	S	Fe
0.20	1.49	1.52	0.58	0.051	0.0086	0.0036	Bal.

Fig. 1 Schematic illustration of Q-P-T and Q&T heat treatment processes: a Q-P-T process; b Q&T process

Fig. 2 Schematic diagram of bar–specimen assembly used in typical SHPB setup

Fig. 3 The engineering stress–strain curves of Q-P-T steel and Q&T steel under different strain rates

Fig. 4 XRD spectra of Q-P-T steel a, Q&T steel b before and after compression

Fig. 5 SEM images of Q-P-T steel before compression a, compressed at strain rates of 7 × 102 s-1b, 5 × 103 s-1c

Fig. 6 SEM images of Q&T steel before compression a, compressed at strain rates of 7 × 102 s-1b, 5 × 103 s-1c

Fig. 7 TEM images of Q-P-T steel compressed at strain rate of 7 × 102 s-1: a bright-field image; b SAED pattern and dark-field image of retained austenite

Fig. 8 TEM images of Q-P-T steel compressed at strain rate of 7 × 102 s-1: a the dislocation configuration in martensite laths; b magnified image of the dislocation configuration in Fig. 8a

Fig. 9 TEM images of Q-P-T steel compressed at strain rate of 5 × 103 s-1: a micro-shear band in a lath; b SAED pattern; c dislocation cells

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