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Vol.29, No.7, 732 ~ 740, 1991
Title
The Effect of Working on Densification and Microstruture of Powder Forged AISI 4640 Steels
이재성Jai Sung Lee, 배광욱Kwang Wook Bae
Abstract
An investigation has been performed on the effect of working on densification and microstructure of powder forged AISI 4640 steels. The densification by powder forging was remarkably improved as the degree of working increased. e. g. the highest density near full densification (∼98%) was achieved in the 50% deformed specimen. The microstructure of prior austenite grains revealed that the full densification by powder forging results from the pore elimination by material flow into pores. The line broadening analysis of X-ray diffraction patterns indicated that the considerable effect of HTMT (high temperature thermomechanical treatment) can be induced by powder forging process. This phenomenon was confirmed by the refinement of martensite structure in the forged specimens. The decrease of hardness during tempering was appreciably retarded with increasing working degree. This is believed to be mainly due to the activated precipitation of fine alloy carbide and its related refinement of tempered martensite structure by HTMT effect.
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