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Title: Effects of silicon on structures and properties of AISI 4320 low alloy steel

Abstract

The effects of 2 percent silicon addition on the structures and properties in AISI 4320 steel were studied; transmission electron microscopy was extensively used to characterize the microstructures. In as-quenched and tempered martensite, silicon additions increase the temperature range in which epsilon carbide exists, delay the cementite precipitation and retained austenite decomposition to higher temperatures. The silicon addition increases the yield and ultimate tensile strength, but deteriorates the Charpy impact toughness except in the tempering range 200-300/sup 0/C. This is mainly due to more internal twinning structure and more coarse or continuous carbide films precipitation along the martensite lath boundaries. Tempered martensite embrittlement is raised from around 200-300/sup 0/C to around 350-550/sup 0/C. Different mechanisms are proposed for normal silicon and high silicon steels. In isothermal transformation bainite structures, silicon additions increase the utlimate tensile strength, but decrease the yield strength due to large amounts of retained austenite entrapped between bainitic ferrites. Silicon addition retard the carbide precipitation rate, suppress the carbide precipitation inside the ferrite laths and promotes coarser carbide precipitation along the bainitic ferrite boundaries and so strongly deteriorates the impact toughness property.

Authors:
Publication Date:
Research Org.:
California Univ., Berkeley (USA). Lawrence Berkeley Lab.
OSTI Identifier:
7197523
Report Number(s):
LBL-4500
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SILICON ALLOYS; MECHANICAL PROPERTIES; MICROSTRUCTURE; STEELS; AUSTENITE; BAINITE; CEMENTITE; EMBRITTLEMENT; MARTENSITE; PRECIPITATION; YIELD STRENGTH; ALLOYS; CARBIDES; CARBON ADDITIONS; CARBON COMPOUNDS; CRYSTAL STRUCTURE; INTERMETALLIC COMPOUNDS; IRON ALLOYS; IRON BASE ALLOYS; IRON CARBIDES; IRON COMPOUNDS; SEPARATION PROCESSES; TRANSITION ELEMENT COMPOUNDS; 360102* - Metals & Alloys- Structure & Phase Studies; 360103 - Metals & Alloys- Mechanical Properties

Citation Formats

Huang, J S. Effects of silicon on structures and properties of AISI 4320 low alloy steel. United States: N. p., 1975. Web.
Huang, J S. Effects of silicon on structures and properties of AISI 4320 low alloy steel. United States.
Huang, J S. Mon . "Effects of silicon on structures and properties of AISI 4320 low alloy steel". United States.
@article{osti_7197523,
title = {Effects of silicon on structures and properties of AISI 4320 low alloy steel},
author = {Huang, J S},
abstractNote = {The effects of 2 percent silicon addition on the structures and properties in AISI 4320 steel were studied; transmission electron microscopy was extensively used to characterize the microstructures. In as-quenched and tempered martensite, silicon additions increase the temperature range in which epsilon carbide exists, delay the cementite precipitation and retained austenite decomposition to higher temperatures. The silicon addition increases the yield and ultimate tensile strength, but deteriorates the Charpy impact toughness except in the tempering range 200-300/sup 0/C. This is mainly due to more internal twinning structure and more coarse or continuous carbide films precipitation along the martensite lath boundaries. Tempered martensite embrittlement is raised from around 200-300/sup 0/C to around 350-550/sup 0/C. Different mechanisms are proposed for normal silicon and high silicon steels. In isothermal transformation bainite structures, silicon additions increase the utlimate tensile strength, but decrease the yield strength due to large amounts of retained austenite entrapped between bainitic ferrites. Silicon addition retard the carbide precipitation rate, suppress the carbide precipitation inside the ferrite laths and promotes coarser carbide precipitation along the bainitic ferrite boundaries and so strongly deteriorates the impact toughness property.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1975},
month = {12}
}

Technical Report:
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