T. Wei, Academy of Armored Force Engineering, Beijing, China
Abstract HAZ / WM (Weld Metal) interfacial microstructure is very important to control and improve the HAZ / WM interfacial crack resistance. In this paper, the interfacial microstructure was observed in the as-welded TWE312/ 616 high-strength armored steel weldment (an austenite / martensite dissimilar metal welded joint) by means of SEM or TEM respectively. It was found that the HAZ / WM interface zone was 10~30 micrometers in width and occupied by weld bond and austenite-rich zone (as shown in Fig. 1). The microstructure in weld bond was so-called martensite-like layer (as seen in Fig. 2), which was composed of complicated multi-phase microstructures like lathe martensite, austenite and so on. The nanohardness distribution across the traverse as- welded TWE312 / 616 armored steel weldment was investigated by means of Nano Test 600 machine. Maximum nanohardness readings were observed in austenite-rich zone and the nanohardness level both in weld bond and true HAZ just next to the weld bond were less than those in austenite-rich zone (as illustrated in Fig. 3). And this was attributed to the working hardening effects of the plastic-deformed austenite. Furthermore, chemical elements distributions across the transverse weld interface were analyzed by AES and the role of element carbon was discussed. The results indicated that carbon redistribution has important influence on the microstructure and mechanical properties of the HAZ / WM interface (as indicated in Fig. 4). Key words: Weld interface; weld bond; austenite-rich zone; microstructure; strength mismatch; armored steel
Acknowledgement This work was supported by National Natural Science Foundation of P. R. China under the grant No. 50574097
Summary: The interfacial microstructure was investigated in the as-welded TWE312/ 616 high-strength armored steel weldment (an austenite / martensite dissimilar metal welded joint) by means of SEM, TEM ,AES and nanoindentation respectively. It was found that the HAZ / WM interface zone was 10~30 micrometers in width and occupied by weld bond and austenite-rich zone. The microstructure in weld bond was so-called martensite-like layer. Maximum nanohardness readings were observed in austenite-rich zone and this was attributed to the working hardening effects of the plastic-deformed austenite. The results indicated that carbon redistribution has important influence on the microstructure and mechanical properties of the HAZ / WM interface.
