The critical time and critical cooling rate of non-equilibrium grain-boundary segregations

1988 ◽  
Vol 7 (3) ◽  
pp. 241-242 ◽  
Author(s):  
Tingdong Xu
Keyword(s):  
Grain Boundary ◽  
Cooling Rate ◽  
Critical Time ◽  
Critical Cooling Rate ◽  
Grain Boundary Segregations ◽  
Non Equilibrium

Computational Program for Non-Equilibrium Grain Boundary Segregation Kinetics

2008 ◽  
Vol 385-387 ◽  
pp. 65-68
Author(s):  
Jun Wang ◽  
Qing Fen Li ◽  
Er Bao Liu
Keyword(s):  
Grain Boundary ◽  
Process Analysis ◽  
Kinetic Equations ◽  
Boundary Segregation ◽  
Critical Time ◽  
Numerical Data ◽  
Grain Boundary Segregation ◽  
Computational Program ◽  
Time Calculation ◽  
Non Equilibrium

The solute segregation to grain boundaries may be classified into equilibrium and non-equilibrium segregation. The models and kinetics calculation equations were proved in previous work. However, the computational task for grain-boundary segregation kinetics process is complex and cumbersome as it can involve a vast amount of numerical data. It is therefore necessary to develop an easily usable computational program which can provide the researchers with a powerful tool in grain-boundary segregation kinetics process analysis in addition to having a sound theory. A computational program of non-equilibrium grain-boundary segregation (NGS) kinetics of solute is therefore developed in this paper. It includes programs for critical time calculation, effective time calculation and diffusion coefficients calculation, the program of Auger Electron Spectroscopy test data disposal, the program of curve fitting and the program of NGS kinetics simulation. A simulation example by using the computation program of NGS kinetic equations is in good accordance with the experimental observation of phosphorus in steel 12Cr1MoV. The computational program of NGS is therefore proved to be appropriate and helpful.

Experimental Studies of Non-Equilibrium Grain-Boundary Segregations of Phosphorus under Low Tensile Stresses

2007 ◽  
Vol 353-358 ◽  
pp. 396-399
Author(s):  
Yu Dong Fu ◽  
Gang Wang ◽  
Chen Liu ◽  
Qing Fen Li
Keyword(s):  
Grain Boundary ◽  
Experimental Studies ◽  
Boundary Segregation ◽  
Critical Time ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Different Temperatures ◽  
Alloy Steels ◽  
The Relationship ◽  
Non Equilibrium

In the present paper, the non-equilibrium grain-boundary segregation of P atom was studied in low alloy steels subjected to a low tensile stress at different temperatures. The AES (Auger electron spectroscopy) experiments and dynamic analyses were conducted to study on the non-equilibrium grain-boundary segregation of P atom. The research results show that non-equilibrium segregation of phosphorus occurred at the grain boundaries of the steels 2.25Cr1Mo and 12Cr1MoV, while the critical time reached about 0-1 hour at constant temperatures 773 and 813K. The relationship between the diffusion rate and the diffusion time for the complex and the phosphorus atom was investigated based on the experimental results. Eventually the diffusion coefficients of complex and P were calculated with using a proposed dynamic model.

Study on Non-Equilibrium Grain-Boundary Segregation of Sulfur among Hastelloy X

2011 ◽  
Vol 181-182 ◽  
pp. 861-865
Author(s):  
Ming Yang ◽  
Yu Jing Nie
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Critical Time ◽  
Grain Boundary Segregation ◽  
Main Element ◽  
Sulfur Segregation ◽  
Hastelloy X ◽  
Nickel Based Alloy ◽  
Equilibrium Segregation ◽  
Non Equilibrium

Sulfur is the main element which caused Nickel-based alloy embrittlement. In this study, the sulfur in Hastelloy X superalloy was determinated with Auger Electron Spectroscopy (AES) for samples quenched from 1180 °C and aged at 500 °C for different time. Experiments results confirmed the non-equilibrium segregation characteristics of sulfur. The results showed that a segregation peak of sulfur is at about 20 min during ageing. This peak was satisfactorily elucidated by the theory of non-equilibrium grain-boundary segregation. By theoretical calculation, the critical time constant of impurities sulfur atom in the Hastelloy X δs= 357. At the same time, the result provides a theoretical basis for sulfur segregation mechanism.

Grain Boundary Fracture Behavior and Segregation of P under Low Tensile Stresses in Steel 2.25Cr1Mo and 12Cr1MoV

2013 ◽  
Vol 577-578 ◽  
pp. 193-196
Author(s):  
Yu Dong Fu ◽  
Qing Fen Li
Keyword(s):  
Grain Boundary ◽  
Fracture Behavior ◽  
Boundary Segregation ◽  
Critical Time ◽  
Fracture Rate ◽  
Phosphorus Segregation ◽  
Tensile Stresses ◽  
Grain Boundary Fracture ◽  
Boundary Fracture ◽  
Non Equilibrium

Experimental investigation about the grain boundary fracture behavior and segregation behavior of phosphorus under low tensile stresses in steel 2.25Cr1Mo and 12Cr1MoV was carried out in this paper. AES (Auger electron spectroscopy) experiments and dynamic analyses on the non-equilibrium grain-boundary segregation (NGS) of phosphorus and the SEM photos of grain boundary fracture in Auger specimens of both steels were obtained. The variation of phosphorus segregation level in grain boundary at different aging time was studied. Results show that the non-equilibrium segregation of phosphorus occurred at the grain boundaries in the two steels while subjected to a tensile stress of 30MPa and held at 500°C. The corresponding critical time was about 1 hour for steel 2.25Cr1Mo and 3.5hour for steel 12Cr1MoV respectively. SEM photos of grain boundary fracture in Auger specimens of the test steels show that the grain boundary fracture rate increased with increasing concentration of phosphorus, and that the fracture toughness of steel 12Cr1MoV is much lower than the one of steel 2.25Cr1Mo.

scholarly journals Investigation of the Quench Sensitivity of an AlSi10Mg Alloy in Permanent Mold and High-Pressure Vacuum Die Castings

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1876 ◽  
Author(s):  
Mengyun Liu ◽  
Zhan Zhang ◽  
Francis Breton ◽  
X.-Grant Chen
Keyword(s):  
High Pressure ◽  
Cooling Rate ◽  
Aluminum Matrix ◽  
Critical Time ◽  
Permanent Mold ◽  
Temperature Property ◽  
Critical Cooling Rate ◽  
Quench Sensitivity ◽  
Die Castings ◽  
Nose Temperature

The quench sensitivities of an AlSi10Mg alloy in permanent mold (PM) and high-pressure vacuum die (HPVD) castings were investigated with time–temperature–transformation and time–temperature–property diagrams using an interrupted quench technique. The quench-sensitive temperature range of the HPVD casting sample is 275–450 °C, and its nose temperature is 375 °C. The quench-sensitive range of the PM casting sample is 255–430 °C, and the nose temperature is 350 °C. The mechanical strength versus the cooling rate in both casting samples were predicted via a quench factor analysis and verified experimentally. The critical cooling rate of the HPVD casting sample is 20 °C/s whereas it is 17 °C/s for the PM casting sample. With a shorter critical time, higher nose temperature, and higher critical cooling rate, the HPVD casting sample exhibits a higher quench sensitivity than the PM casting sample. The differences in the quench sensitivities of the AlSi10Mg alloy due to the different casting processes is explained via the different precipitation behavior. At the nose temperature, coarse β-Mg2Si precipitates mainly precipitate along the grain boundaries in the HPVD casting sample, whereas rod-like β-Mg2Si precipitates distribute in the aluminum matrix in the PM casting.

Effects of RE on Critical Cooling Rate of Bearing-B Steel

2012 ◽  
Vol 535-537 ◽  
pp. 761-763 ◽  
Author(s):  
Yi Sheng Zhao ◽  
Xin Ming Zhang ◽  
Zhi Guo Gao
Keyword(s):  
Phase Change ◽  
Cooling Rate ◽  
Experimental Results ◽  
Cooling Rates ◽  
Critical Cooling Rate ◽  
The Law

The law of phase change of bearing-B steel during continual cooling was studied by adopting dilatometer. The CCT curves of bearing-B steel were drawn, and the effects of RE on critical cooling rates were studied. The experimental results show that the start temperatures of martensite TM was decreased from 438 to 404°C. The critical cooling rate was simultaneously decreased from 33 to 15°C/s.

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