Microstructure-Toughness Relationship in AISI4340 Steel

2011 ◽  
Vol 312-315 ◽  
pp. 110-115
Author(s):  
N. Saeidi ◽  
A. Ekrami
Keyword(s):  
Transition Temperature ◽  
Charpy Impact ◽  
Brittle Transition ◽  
Hardness Tests ◽  
Ductile Brittle Transition Temperature ◽  
Different Temperatures ◽  
Ferrite Steel ◽  
Brittle Transition Temperature ◽  
Impact Data ◽  
Aisi4340 Steel

To improve the strength and toughness of AISI 4340 steel, different microstructures, containing full bainite, bainite-ferrite, martensite-ferrite and full martensite were produced by different heat treatment cycles. Tensile, impact and hardness tests were carried out at room temperature. The ductile-brittle transition temperature was determined from impact data at different temperatures. The results showed that steel with bainite - 0.34 ferrite microstructure has the highest elongation and charpy impact energy, while its tensile strength and yield stress decreased in comparison to other microstructures. This increment was noticeable when bainite - 0.34 ferrite steel was tempered. The ductile-brittle transition temperature decreased with tempering of bainite -0.34 steel. The fracture surface analysis of charpy specimens also showed an increase in toughness of tempered bainite-ferrite in comparison to other microstructures.

Evaluation of Ductile/Brittle Failure Theory and Derivation of the Ductile/Brittle Transition Temperature

2015 ◽  
Vol 83 (2) ◽  
Author(s):  
Richard M. Christensen
Keyword(s):  
Transition Temperature ◽  
Brittle Failure ◽  
Evaluation Process ◽  
Isotropic Materials ◽  
Brittle Transition ◽  
Failure Theory ◽  
Ductile Brittle Transition Temperature ◽  
Brittle Transition Temperature ◽  
Materials Failure

A recently developed ductile/brittle theory of materials failure is evaluated. The failure theory applies to all homogeneous and isotropic materials. The determination of the ductile/brittle transition is an integral and essential part of the failure theory. The evaluation process emphasizes and examines all aspects of the ductile versus the brittle nature of failure, including the ductile limit and the brittle limit of materials' types. The failure theory is proved to be extraordinarily versatile and comprehensive. It even allows derivation of the associated ductile/brittle transition temperature. This too applies to all homogeneous and isotropic materials and not just some subclass of materials' types. This evaluation program completes the development of the failure theory.

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