Study of the martensite structure at the weld interface and the fracture toughness of dissimilar metal joints
- Beijing Polytechnic Univ., Beijing (China). Dept. of Materials Science and Engineering
In austenitic-ferritic dissimilar metal welded joints, the content of alloying elements in the transition zone varies continuously from the heat-affected zone (HAZ) to the weld metal. Due to the low level of Ni content, a martensite layer is formed in this zone during the welding process. The Charpy impact test performed previously by other researchers indicated that the martensite layer was the weakest zone in toughness in the joints. In this study, color metallography and transmission electron microscope (TEM) analysis were used to show the martensite structures at the weld interface. The results show that the structures of the martensite layer at the weld interface are lath martensite. The martensite starting points vary with the distance from the fusion line and are controlled by composition gradient. The boundary of the transition zone could be divided into two types: the blurred type, and the sharp type, which are controlled by diffusion of elements. A simulation test, in which specimens were prepared by casting steels in accordance with the compositions of the martensite layer, was conducted to evaluate the fracture toughness of the martensite layer. The experiments were also made to investigate the distribution of toughness in the different regions of the joints. The results show that the weakest region in toughness in the dissimilar metal joints is not the martensite layer but the overheated zone in HAZ.
- OSTI ID:
- 6273494
- Journal Information:
- Welding Journal (Miami); (United States), Vol. 72:8; ISSN 0043-2296
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHROMIUM-MOLYBDENUM STEELS
WELDING
WELDED JOINTS
FRACTURE PROPERTIES
MICROSTRUCTURE
CHARPY TEST
HEAT AFFECTED ZONE
INTERFACES
MARTENSITE
NICKEL
POWER PLANTS
TRANSMISSION ELECTRON MICROSCOPY
ALLOYS
CARBON ADDITIONS
DESTRUCTIVE TESTING
ELECTRON MICROSCOPY
ELEMENTS
FABRICATION
IMPACT TESTS
IRON ALLOYS
JOINING
JOINTS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
METALS
MICROSCOPY
TESTING
TRANSITION ELEMENTS
ZONES
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties