B Eghbali
,
M Shaban
钢铁研究学报(英文版)
Grain refinement in a plain carbon steel under intercritical warm deformation was studied by torsion testing. Based on the experimental results, the warm flow behaviour and microstructural evolution of ferrite were researched with particular emphasis on the effect of the strain rate in controlling the grain refinement mechanism of ferrite. The deformed microstructures were investigated at various strain rates using optical microscopy and electron back-scattered diffraction (EBSD). The EBSD observations indicate that an increase in the strain rate leads to the development of new fine ferrite grains with high angle boundaries. Furthermore, it shows that the annihilation of dislocations occurs more readily at lower strain rate. The elongated ferrite grains continuously dynamically recrystallize to form the equiaxed fine ferrite grains. Thereby, the aspect ratio of elongated grains decreases with increasing the strain rate. Furthermore, the peak stress and steady state stress of ferrite both increase with increasing strain rate. Based on the study, the effect of strain rate on the development of fine ferrite grains during continuous dynamic recrystallization of ferrite was analyzed in detail.
关键词:
grain refinement
,
steel
,
strain rate
,
torsion testing
,
EBSD
B Eghbali
,
M Shaban
钢铁研究学报(英文版)
Hot torsion testing was performed on a low carbon Nb-Ti microalloyed steel to study the effects of hot torsion parameters, strain and strain rate, on ultrafine ferrite grains production through dynamic strain-induced transformation, at a deformation temperature just above Ar3. The initiation and evolution of ultrafine ferrite grains were studied. The results show that the amount of strain and strain rate has conversely effect on the volume fraction and grain size of ultrafine ferrite grains. With increasing strain, the interior of austenite grains become activated as nucleation sites for fine ferrite grains. As a result, ferrite grains continuously nucleate not only at the former austenite grain boundaries but also inside the austenite grains which leads to a rapid increase in volume fraction of ultrafine grains. Increasing of strain rate reduces the tendency of ferrite grains coarsening so that ultrafine ferrite grains are achieved, while the volume fraction of ultrafine grains decreases at the same strain level.
关键词:
dynamic strain induced transformation
,
grain refinement
,
ferrite
,
hot torsion
,
steel
V Soleymani
,
B Eghbali
钢铁研究学报(英文版)
Grain refinement is one of the successful and low-cost methods to develop metals having excellent combination of strength and ductility. Low carbon steel was deformed by using multidirectional forging (MDF) technique at room temperature. The influence of strain amount and annealing process on the microstructure and mechanical properties of investigated steel was studied. The grain refinement mechanism was studied by the microstructure observation. The results showed that the grain refinement was attained by multidirectional forging technique. The initial coarser grains of average 38 μm size fragmented into very fine ferrite with grain sizes of about 1.2 μm. After MDF, the strength properties improved significantly, although uniform elongation and elongation decreased with increasing strain.
关键词:
multidirectional forging
,
grain refinement
,
annealing
,
steel
,
recrystallization
Journal of Alloys and Compounds
The isothermal section at 700 degrees C in the Co-rich ternary Sm-Co-B system was determined by means of X-ray diffraction. In this range, nine ternary borides were observed: Sm3Co13B2, SmCo4B, Sm3Co11B4, Sm2Co7B3, SmCo3B2, Sm2Co14B, SmCo12B6, SmCo4B4, SmCo2B2. The first five borides are members of the homologous series Smm + nCo5m + 3nB2n formed by alternative stacking m layers of SmCo5 with n layers of SmCo3B2 along the c-axis. The compound Sm3Co13B2 was not reported in previous isothermal sections found in the literature. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
Sm-Co-B;phase diagram;magnetic-properties
Journal of Alloys and Compounds
The isothermal section at 700 degrees C in the Go-rich ternary Gd-Co-B system was determined by means of x-ray diffraction. In this range, nine ternary borides were observed: Gd3Co13B2, GdCo4B, Gd3Co11B4, Gd(2)Go(7)B(3), GdCo3B2 Gd2Co14B, GdCo12B6, GdCo4B4, GdGo(2)B(2). This isothermal section at 700 degrees C is similar to other isothermal sections found in the literatures, but they do not include the compounds Gd3Co13B2 and Gd2Co14B. The first five borides are members of the homologous series Gdm + nCo5m + 3nB2n, which is formed by alternative stacking of m layers of GdCo5 with n layers of GdCo3B2 along the c-axis. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
Gd-Co-B;phase diagram;earth
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms
We have applied the embedded atom method (EAM). to calculate boundary concentration distributions of Ni, Al and B, and B probabilities in the "interstitial" and, the "substitutional" sites, at the Ni3Al-x at.% B (100% Ni\100% Ni) [001]/Sigma5(210)/36.87 degrees. grain boundary at the equilibrium. We propose that the bulk effects of B on the grain boundary include the positive effect on the Ni enrichment at the grain boundary, i.e. the B atoms induce Ni atoms to substitute into Al sites, the negative effect on it, i.e. the B atoms substitute into Ni sites, and the neutral effect on it, i.e. the B atoms insert into interstices in the grain boundary. Our calculations show that owing to combination of the positive effect and the negative effect, corresponding to B-enrichment increasing, the Ni-enrichment and the Al-depletion become more and more obvious, when x increases from 0.1 to 0.5. Then, corresponding to B-enrichment decreasing, the Ni-enrichment and the Al-depletion also become more and more obvious, when x decreases from 0.9 to 0.5. Thus, between low (x = 0.1) and high (x = 0.9) B bulk concentrations, there is a B bulk concentration (x = 0.5), at which the Ni-enrichment and the Al-depletion become the most obvious, even if Ni is approximately saturated. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
computer-simulation;boron;segregation;fracture;metals;alloys
金属学报
Volu扣ne 27SeriesB1991AUTHOR INDEX CCAO Guanghan(曹光旱)············……6一B科6CAo weijie(曹卫恋)..················……5一B32oCAO Yilin(曹益林)··················……6一B443CHANG Xin(常听)···············……1一B48CHE Guang邻n(车广灿)·············一6一B科0CHEN Erbao(陈二保)···············……6一B410CHEN Jia....
关键词:
Journal of Alloys and Compounds
Nd-Fe-(B.C) alloys have been synthesized by mechanical alloying and subsequent heat-treatment, with B4C as one of the starting materials. It is found that when the pure B4C is milled alone, it proves difficult to decompose. When the B4C compound is milled with Nd and Fe, the complete decomposition of B4C and the formation of Nd2Fe14(B,C) phase is observed. Furthermore, the competition between B and C atoms for entering the Nd2Fe14B lattice. the effects of the B4C content on the structure and the magnetic properties of Nd2Fe14(B,C)-based alloys are investigated. A coercivity as high as 18.3 kOe and the maximum energy product of 10.4 MGOe have been achieved for the Nd-Fe-(B,C) alloys. (c) 2005 Elsevier B.V. All rights reserved.
关键词:
permanent magnets;mechanical alloying;fe-c alloys;permanent-magnets;r2fe14c;nd
