A Review of the Stress-Relaxation Method for Following the Kinetics of Precipitation, Recovery and Recrystallization

2012 ◽  
Vol 706-709 ◽  
pp. 2758-2763 ◽  
Author(s):  
W.J. Liu
Keyword(s):  
Stress Relaxation ◽  
Relaxation Rate ◽  
Relaxation Method ◽  
Dislocation Model ◽  
Precipitation Kinetics ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

Stress-relaxation method was first used by Liu and Jonas in 1980s for following the kinetics of strain induced precipitation of carbonitrides in austenite. Since then, the method has been widely employed for studying not only the precipitation kinetics but also the recovery and recrystallization processes in steels and other alloys. In the present paper, the principle and the worldwide usage of the method were reviewed. The dependence of stress relaxation rate on the occurrence of precipitation, recovery and recrystallization was interpreted based on a dislocation model. The capabilities and the limitations of the method were discussed and ways to overcome the existing limitations were also proposed.

Influence of Boron on the Precipitation Kinetics in Advanced Ultra-High Strength Steels

2015 ◽  
Vol 1765 ◽  
pp. 91-96
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J.M. Cabrera
Keyword(s):  
Stress Relaxation ◽  
High Strength Steels ◽  
High Strength ◽  
Relaxation Method ◽  
Low Carbon ◽  
Precipitation Kinetics ◽  
Austenite Recrystallization ◽  
Ultra High Strength Steels ◽  
Relaxation Curves ◽  
Kinetics Of

ABSTRACTIn the present work, the stress relaxation method was employed to determine the influence of B addition on the kinetics of strain-induced precipitation and its interaction with the static austenite recrystallization. For this purpose, the behavior of two low carbon advanced ultra-high strength steels was analyzed during stress relaxation tests at different temperatures and constant pre-strain rate. The precipitation start (Ps) and finish (Pf) times were determined from the relaxation curves and then the corresponding precipitation-time-temperature diagrams were constructed for each steel. Transmission Electron Microscopy was used to determine the chemical nature and evolution of precipitation. In general, the results show that the addition of B retards the austenite recrystallization, tends to accelerate the precipitation kinetics of carbonitrides and leads to a finer and denser distribution of precipitates. These results are discussed in terms of the driving force for the nucleation of precipitation, which in turn is controlled by the degree of supersaturation of microalloying element and as a function of B segregation and B-vacancy complexes to dislocations and grain boundaries.

ANOMALOUS STRESS RELAXATION BEHAVIOR OF POLYCRYSTALLINE ALUMINUM AT LOW TEMPERATURE

2007 ◽  
Vol 21 (10) ◽  
pp. 1745-1754 ◽  
Author(s):  
I. M. GHAURI ◽  
NAVEED AFZAL ◽  
M. ANWAR ◽  
S. A. SIDDIQUE
Keyword(s):  
Stress Relaxation ◽  
Relaxation Rate ◽  
Deformation Process ◽  
Tensile Deformation ◽  
Polycrystalline Aluminum ◽  
Rate Processes ◽  
Basic Equations ◽  
Relaxation Curves ◽  
Kinetics Of ◽  
Barrier Model

The tensile deformation of polycrystalline aluminum (99.999%) was studied between 18 and 300 K. The stress-relaxation at constant strain was determined at strain intervals of about 0.5% with total strain exceeding about 3%. Stress-relaxation curves were logarithmic except at large "t" where they flatten. The relaxation rate "s" was determined by using equation s=d(Δσ)/d ln t, where Δσ(t)=σ0-σ(t) is the amount of stress relaxed at any instant of time "t" from the initial stress level σ0 at which relaxation was allowed to start. The slope ds/dσ0 was observed to attain maxima at about 30 K and minima at about 60 K. The undulation in the temperature dependence of stress relaxation rate in the range 18–60 K is an outcome of changes in the substructures of dislocations which have developed during the deformation process. These changes then require stresses higher than that applied in the basic equations which describe the kinetics of the mode of deformation. The average intrinsic height of potential barrier U0, estimated by means of the single barrier model of stress relaxation, was 1.2±0.3 eV. These values appeared to be compatible with the dislocation-dislocation intersection, controlling the rate processes in polycrystalline aluminum.

Effects of Nb on Strain-Induced Precipitation of NbC and Static Recrystallization for High Nb Pipeline Steels

2010 ◽  
Vol 146-147 ◽  
pp. 1315-1321 ◽  
Author(s):  
Gui Ying Qiao ◽  
Fu Ren Xiao ◽  
Xiao Bing Zhang ◽  
Shao Hui Chen ◽  
Bo Liao
Keyword(s):  
Activation Energy ◽  
Stress Relaxation ◽  
Compression Test ◽  
Static Recrystallization ◽  
Pipeline Steel ◽  
Relaxation Technique ◽  
Start Time ◽  
Pipeline Steels ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

Strain-induced precipitation of complex carbonitrides and recrystallization for three high-Nb pipeline steels with different Nb and C content have been studied by using a stress relaxation technique and two-passes interrupted compression test. Sequentially, the PTT diagrams were obtained, and static recrystallization activation energy was calculated. Furthermore, the effects of Nb and C content on strain-induced NbC precipitation and static recrystallization were discussed. The results confirm the faster kinetics of precipitation and its retarded recrystallization in the case of higher Nb pipeline steel, and that the recrystallization is easier in low Nb pipeline steel in comparison to the case of high Nb steel. However, the effects of Nb on strain-induced precipitation and static recrystallization were associated with the Nb/C ratio. The precipitation start time (Ps) of strain-induced NbC is delayed in lower Nb/C ratio pipeline steel. It is suggested that the reduced supersaturation of Nb can result in the delay of precipitation of strain-induced NbC carbides forming in the low Nb/C ratio steel.

Correlation of fatigue behavior and dynamic mechanical properties of hybrid composites of polypropylene/short glass fibers/hollow glass beads

2021 ◽  
pp. 089270572199319
Author(s):  
Gustavo B Carvalho
Keyword(s):  
Stress Relaxation ◽  
Flexural Strength ◽  
Relaxation Rate ◽  
Hybrid Composites ◽  
Fatigue Behavior ◽  
Glass Fibers ◽  
Glass Beads ◽  
Hollow Glass ◽  
Dynamic Mechanical ◽  
Short Glass

Ternary hybrid composites of Polypropylene (PP)/Short Glass Fibers (GF)/Hollow Glass Beads (HGB) were prepared using untreated and aminosilane-treated HGB, compatibilized with maleated-PP, and with varying total and relative GF/HGB contents. Static/short-term flexural strength properties data revealed, through lower flexural strength values, that the presence of untreated HGB particles induces to fiber-polymer interfacial decoupling at much higher extent than in the presence of aminosilane-treated HGB particles. This phenomenon is also evident when evaluating the data from displacement-controlled three-point bending fatigue tests. Monitored up to 106 cycles, the analyzed hybrid composites presented distinct performance relative to their fatigue stress relaxation rate: the lower the matrix-reinforcements’ interfacial adhesion, more pronounced the stress relaxation rate as a function of the number of fatigue cycles. Dynamic Mechanical Thermal Analysis (DMTA) results could successfully reveal the hybrid composites behavior at the microstructural level when they were submitted to both static flexural test and fatigue, depending on the degree of interfacial interactions between the polymer matrix of PP and the hybrid reinforcements of GF and HGB (with and without aminosilane surface treatment).

Kinetics of Precipitation.

1965 ◽  
Vol 87 (6) ◽  
pp. 1414-1414
Author(s):  
Silvester Liotta
Keyword(s):  
Kinetics Of Precipitation ◽  
Kinetics Of

Effect of ECAP Processing on Hardness, Electrical Conductivity, and Precipitation Kinetics of the Cu-0.81Cr-0.07Zr Alloy

2021 ◽  
Author(s):  
Filipe Caldatto Dalan ◽  
Gisele Ferreira de Lima Andreani ◽  
Dilermando Nagle Travessa ◽  
Svetlana Faizova ◽  
Ilshat Albertovich Faizov ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Precipitation Kinetics ◽  
Ecap Processing ◽  
Kinetics Of
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