Correlation of microstructure and tempered martensite embrittlement in two 4340 steels |
| |
Authors: | S Lee D Y Lee R J Asaro |
| |
Affiliation: | (1) Department of Materials Science and Engineering, Pohang Institute of Science and Technology, 790 Pohang, Korea;(2) Division of Engineering, Brown University, 02912 Providence, RI |
| |
Abstract: | This study is concerned with a correlation between the microstructure and fracture behavior of two AISI 4340 steels which
were vacuum induction melted and then deoxidized with aluminum and titanium additions. This allowed a comparison between microstructures
that underwent large increases in grain size and those that did not. When the steels were tempered at 350°C,K
Ic and Charpy impact energy plots showed troughs which indicated tempered martensite embrittlement (TME). The TME results of
plane strain fracture toughness are interpreted using a simple ductile fracture initiation model based on large strain deformation
fields ahead of cracks, suggesting thatK
Icscales roughly with the square root of the spacing of cementite particles precipitated during the tempering treatment. The
trough in Charpy impact energy is found to coincide well with the amount of intergranular fracture and the effect of segregation
of phosphorus on the austenite grain boundaries. In addition, cementite particles are of primary importance in initiating
the intergranular cracks and, consequently, reducing the Charpy energy. These findings suggest that TME in the two 4340 steels
studied can be explained quantitatively using different fracture models. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|