|
|
|
| EFFECT OF ELONGATION ON DISLOCATION STRUCTURE AND CRACK INITIATION OF HARDENED AND TEMPERED 40Mn STEEL |
| LIU Yumen; YANG Guiying (Xi'an Jiaotong University) (Manuscript received 30 July; 1983; revised manuscript 10 October; 1983) |
|
Cite this article:
LIU Yumen; YANG Guiying (Xi'an Jiaotong University) (Manuscript received 30 July; 1983; revised manuscript 10 October; 1983). EFFECT OF ELONGATION ON DISLOCATION STRUCTURE AND CRACK INITIATION OF HARDENED AND TEMPERED 40Mn STEEL. Acta Metall Sin, 1984, 20(4): 242-381.
|
|
|
Abstract The process of deformation and crack initiation of high temper (550℃) medium-carbon steel 40Mn has been investigated using smooth tensile specimens. The midgage length part of the specimen was spark cut into 0.3mm thick sheets. The direct transmission observation of thin foil specimens was carried out on TEM. The evolution of the dislocation structure with elongation in the steel of hardened and tempered condition was studied. In the lath ferrite, the feature of dislocation structure is irregular network. At the stage of comparatively small elongation (δ=0.2-2.7％), near the interface of ferrites and the ferrite-cementite interface, regular dislocation networks appear and the dislocation density increases. At the deformation stage of δ=4.7％, the dislocations tangle and desify. At the deformation stage of δ=6.8-10％, the feature of dislocation structure becomes elongated dislocation cells. The crack nucleation in hardened and tempered steel has been observed by SEM and optical microscope. When the deformation attains δ=4.7％, the submicroscopic cracks are initiated at interface of metal matrix and inclusion. At the deformation stage of δ=6.8％, the submicrocrack initiated at interface of lath ferrites and interface of ferritecementite. The submicroscopic crack propagated through the formation and joining up of void groups.
|
|
Received: 18 April 1984
|
1 Thomas, G., Metall. Trans., 9A (1978) , 439．
2 Nutting, J., J. Iron Steel Inst., 207 (1969) , 872．
3 Speich, G. R., Trans. Metall. Soc. AIME, 245 (1969) , 2553．
4 Tekin, E.; Kelly, P. M., Precipitation From Iron-Base Alloys, Speich, G. R.; Clark, J. B. Eds., Gordon and Breach, New York, 1965, p. 173．
5 Winchell, P. G.; Cohen, M., ASM Trans. Q., 55 (1962) , 347．
6 Kurdjumov, G. V., J. Iron Steel Inst., 195 (1960) , 26．
7 Roberts, C. S.; Averbach, B. L.; Cohen, M., Trans. ASM, 45 (1953) , 576．
8 Honeycombe, R. W. K.; Steels Microstructure and Properties, Edward Arnold, London, 1981．
9 Picketing, F. B., Physical Metallurgy and the Design of Steels, Appl. Sci. Publ., Barking, Essex, Engl., 1978．
10 Honeycombe, R. W. K., Structure and Strength of Alloy Steels, Climax Molybdenum Co., London, 1973．
11 刘禹门,金属热处理学报,3(1982) ,№ 1,1．
12 Keh, A. S.; Spitzig, W. A.; Nakada, Y., Philos. Mag., 23 (1971) , 829． |
| No Suggested Reading articles found! |
|
|
Viewed |
|
|
|
Full text
|
|
|
|
|
Abstract
|
|
|
|
|
Cited |
|
|
|
|
| |
Shared |
|
|
|
|
| |
Discussed |
|
|
|
|
