673K Embrittlement of Ferritic Spheroidal Graphite Cast Iron

1984 ◽  
Vol 34 ◽  
Author(s):  
O. Yanagisawa ◽  
T. S. Lui
Keyword(s):  
Strain Rate ◽  
Intergranular Fracture ◽  
Volume Fraction ◽  
Ferrite Matrix ◽  
Dynamic Strain ◽  
Spheroidal Graphite ◽  
Dynamic Strain Ageing ◽  
Cast Irons ◽  
Hydrostatic Tensile Stress

ABSTRACTIntergranular fracture had been observed in the temperature range from 573K – 673K, where the ductilit miniTum appears at 673K for the strain rate of sec−1 in ferritic spheroidal graphite cast irons.The cause of intergranular fracture at about 673K has been investigated. The following two points are emphasized. The first is the role of hydrostatic tensile stress in triaxial stress field developed in ferrite matrix among graphite nodules, relating to the effect of graphite volume fraction on the intergranular fracture. The second is the role of carbide precipitation during dynamic strain ageing, relating to the strain rate and the temperature dependence of the intergranular fracture.

Investigation of Dynamic Strain Ageing Effects of Low Alloy Steels 15Kh2MFA and 15Kh2NMFA

2005 ◽  
Vol 482 ◽  
pp. 367-370
Author(s):  
Miroslava Ernestová
Keyword(s):  
Strain Rate ◽  
Tensile Tests ◽  
Dynamic Strain ◽  
Low Alloy Steels ◽  
Strain Rates ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Lower Strain ◽  
Wide Range ◽  
Alloy Steels

The paper summarizes results of tensile tests in low alloy steel (LAS) specimens (steels 15Kh2MFA and 15Kh2NMFA). Slow Strain Rate Tensile tests (SSRT) were performed in air at temperatures from 22 to 325°C over a wide range of strain rates from 2.5×10-6 to 1.67×10-3 s-1. The possible effect of strain rate and temperature to mechanical properties of tested LAS is searched for. The dynamic strain ageing (DSA) was observed within certain temperature ranges at lower strain rates tested and its hardening effect in terms of the maximum strengthening stress decreased linearly with the increase of log strain rate. It has been found that the occurrence of susceptibility to environmentally assisted cracking (EAC) of tested steels in high temperature water (HTW) is corelated to the DSA behavior. The result suggest that DSA reduces ductility of reactor pressure vessel (RPV) steel and its role in enhancing the EAC of RPV steels should not be neglected, in view of the coincidence with susceptibility zones for DSA and EAC in terms of strain rate and temperature. A reasonable coincidence was observed between the susceptibility to DSA exhibited by SSRT in air and with the EAC behavior observed in laboratory experiments.

scholarly journals On the role of impurities on spheroidal graphite degeneracy in cast irons

Carbon ◽  
2021 ◽  
Vol 172 ◽  
pp. 529-541
Author(s):  
Bernadette Domengès ◽  
Mayerling Martinez Celis ◽  
Florent Moisy ◽  
Jacques Lacaze ◽  
Babette Tonn
Keyword(s):  
Spheroidal Graphite ◽  
Cast Irons ◽  
Graphite Degeneracy

Superplasticity in Coarse-Grained Al-Mg Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 1285-1290 ◽  
Author(s):  
Ehab Samuel ◽  
John J. Jonas ◽  
F.H. Samuel ◽  
S.R. MacEwen
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Mg Alloys ◽  
Coarse Grained ◽  
High Temperature Deformation ◽  
Dynamic Strain ◽  
Temperature Deformation ◽  
Dynamic Strain Ageing ◽  
Strain Ageing ◽  
Al Mg Alloys

Superplasticity refers to a high temperature deformation process involving a marked sensitivity of the flow stress to the imposed strain rate, with resulting enhanced ductility. Although conventionally associated with fine-grained materials, superplasticity has recently been observed in coarse-grained alloys. The present research involves the deformation behavior of Al-Mg base alloys, where superpure Al-3%Mg and Al-5%Mg, and commercial Al 5056 were selected for study. The results for the Al-5%Mg and Al 5056 alloys are presented in this article. Flat sheet-type samples were tensile tested to 10% strain at increasing temperatures and at prescribed strain rates (0.001/s, 0.01/s, and 0.1/s). The dependence of flow stress on temperature was found to display some unusual characteristics. This behavior is interpreted as resulting from the occurrence of dynamic strain ageing (DSA). The aim of the overall study is to determine the relation between DSA and superplasticity in coarse-grained Al-Mg alloys. This will, in turn, lead to the control of the strain ageing behavior so as to produce the largest possible values of strain rate sensitivity (and, hence, elongation).

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