Microstructue and mechanical properties of AISI 4340 steel modified with aluminum and silicon

Technical Report · Tue Feb 01 04:00:00 EST 1977

DOI:https://doi.org/10.2172/7215788· OSTI ID:7215788

Bhat, M S

The influence of additions of aluminum and combinations of aluminum and silicon to AISI 4340 steels was investigated. The mechanical properties such as strength, fracture toughness (K/sub Ic/), and impact toughness (C/sub v/) were obtained for the modified steels in the quenched and tempered condition. The microstructure was characterized using optical and transmission electron microscopy. The fracture surfaces and inclusions were characterized using scanning electron microscopy and an energy dispersive analysis of x-rays unit. It was observed that the softening which normally occurs on tempering AISI 4340 steel was retarded by additions of either aluminum or combinations of aluminum and silicon. The effect of aluminum on the tempering reactions in steel appeared to be similar to that of silicon. The tempered martensite embrittlement phenomenon in AISI 4340 steel occurred at higher tempering temperatures in the presence of silicon and/or aluminum. Significant improvements in the strength and toughness of quenched and tempered 4340 steel were obtained through silicon and/or aluminum additions. An attempt was made to correlate microstructure with the observed mechanical properties. The fracture surfaces features associated with the initiation of fast fracture for all the heat treated conditions investigated indicated that the operative fracture mode was complex.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7215788
• Report Number(s): LBL-6046
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
ALUMINIUM
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
ELEMENTS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALS
MICROSCOPY
MICROSTRUCTURE
SEMIMETALS
SILICON
SILICON ADDITIONS
SILICON ALLOYS
STEELS