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

Technical Report · Mon Dec 01 04:00:00 EST 1975

DOI:https://doi.org/10.2172/7197523· OSTI ID:7197523

Huang, J S

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.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• OSTI ID: 7197523
• Report Number(s): LBL-4500
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
AUSTENITE
BAINITE
CARBIDES
CARBON ADDITIONS
CARBON COMPOUNDS
CEMENTITE
CRYSTAL STRUCTURE
EMBRITTLEMENT
INTERMETALLIC COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
IRON CARBIDES
IRON COMPOUNDS
MARTENSITE
MECHANICAL PROPERTIES
MICROSTRUCTURE
PRECIPITATION
SEPARATION PROCESSES
SILICON ALLOYS
STEELS
TRANSITION ELEMENT COMPOUNDS
YIELD STRENGTH