Bulk Nanocrystalline Ferrite Stabilized through Grain Boundary Carbon Segregation

The effect of interstitial and substitutional impurities on grain boundary (GB) cohesion in the series of B2-TiMe alloys is studied from first principles using pseudopotential approach. It is shown that the TiMe Σ5(310) symmetrical tilt GB cohesion is reduced by the segregation of hydrogen while it is increased due to boron or carbon segregation. We analyze also the combined and accumulation effect of interstitial B (C) and H impurities on the change of the Griffith work.

Download Full-text

Effect of Grain Size and Annealing Condition on Grain Boundary Segregation of Carbon Atoms in ULC Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.302.286 ◽

2013 ◽

Vol 302 ◽

pp. 286-291

Author(s):

Yan Cui ◽

Ai Min Ji ◽

Yun Li Feng ◽

Rui Zhen Wang ◽

Qi Long Yong

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Grain Boundaries ◽

Boundary Segregation ◽

Grain Boundary Segregation ◽

Annealing Condition ◽

Bake Hardening ◽

Cooling Rates ◽

Carbon Segregation

The grain boundary segregation of carbon atoms is influenced by grain size and annealing condition. Increasing grain size and improving the final cooling ( ＜400 oC) rate can improve the bake hardening property, due to the decreasing of carbon segregation at grain boundaries. Cooling rates have a great effect on bake hardening property of ULC steel with smaller grains

Download Full-text

Grain Boundary Internal Friction Peak in Nanocrystalline Aluminum Studied by Continuously Changing-Temperature

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1004-1005.3 ◽

2014 ◽

Vol 1004-1005 ◽

pp. 3-9

Author(s):

Jian Ning Wei ◽

Li Ling Zhou ◽

Jian Qiang Liu ◽

Xue Yun Zhou ◽

Wei Jun Xie

Keyword(s):

Internal Friction ◽

Grain Boundary ◽

Dynamic Modulus ◽

Vibration Measurement ◽

Heating Process ◽

Internal Friction Peak ◽

Low Frequencies ◽

Exponential Factor ◽

Nanocrystalline Aluminum ◽

Bulk Nanocrystalline

The bulk nanocrystalline aluminum are fabricated by cryomilling and hot-press sintering. The internal friction (IF) and relative dynamic modulus measurements in the nanocrystalline aluminum (Al) have been made using a multifunction internal friction apparatus (MFIFA) at low frequencies (0.2-3.0 Hz) over the wide temperature ranges from room temperature to 450 °C, while continuously changing-temperature forced vibration measurement. In the temperature spectrums of IF during heating process and cooling process, a distinct IF peak is found. Corresponding to the IF peak, the relative dynamic modulus decreases rapidly. The peak temperature of the IF peak shifts towards higher temperature with increasing frequency, i.e., the IF peak seem due to the thermal activated relaxation process. The IF peak is a grain boundary IF peak, which is associated with the diffusive grain boundary of Al/Al. Its activation energy has been calculated to be 2.21±0.04×10-19J and the pre-exponential factor is 10-14s in IF measurements.

Download Full-text