Application of an Equiaxed Grain Growth and Transport Model to Study Macrosegregation in a DC Casting Experiment

An essentially fully acicular alpha-prime martensite within an equiaxed grain structure was produced in an Electron Beam Melting (EBM)-fabricated Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy using two different Arcam EBM machines: An A2X system employing tungsten filament thermionic electron emission, and a Q20 system employing LaB6 thermionic electron emission. Post-process Hot Isostatic Pressing (HIP) treatment for 2 h at 850, 950, and 1050 °C resulted in grain refinement and equiaxed grain growth along with alpha-prime martensite decomposition to form an intragranular mixture of acicular martensite and alpha at 850 °C, and acicular alpha phase at 950 and 150 °C, often exhibiting a Widmanstätten (basketweave) structure. The corresponding tensile yield stress and ultimate tensile strength (UTS) associated with the grain growth and acicular alpha evolution decreased from ~1 and ~1.1 GPa, respectively, for the as-fabricated Ti6242 alloy to ~0.8 and 0.9 GPa, respectively, for HIP at 1050 °C. The optimum elongation of ~15–16% occurred for HIP at 850 °C; for both EBM systems. Because of the interactive role played by equiaxed grain growth and the intragrain, acicular alpha microstructures, the hardness varied only by ~7% between 41 and 38 HRC.

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Comparison of two-phase and three-phase macroscopic models of equiaxed grain growth in solidification of binary alloy with electromagnetic stirring

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/861/1/012026 ◽

2020 ◽

Vol 861 ◽

pp. 012026

Author(s):

T Wang ◽

S Semenov ◽

E Wang ◽

Y Delannoy ◽

Y Fautrelle ◽

...

Keyword(s):

Grain Growth ◽

Binary Alloy ◽

Electromagnetic Stirring ◽

Two Phase ◽

Macroscopic Models ◽

Three Phase ◽

Equiaxed Grain

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Effects of Electromagnetic Stirring on the Solidified Microstructure of Martensite Stainless Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.106 ◽

2012 ◽

Vol 152-154 ◽

pp. 106-111

Author(s):

Guo Feng Zhan ◽

En Gang Wang ◽

En Jiang ◽

Zai Wei Jiang ◽

Ji Cheng He

Keyword(s):

Stainless Steel ◽

Electromagnetic Stirring ◽

Maximum Value ◽

The Matrix ◽

Steel Ingots ◽

Casting Experiment ◽

Equiaxed Grains ◽

Equiaxed Grain

In this text, the effect of electromagnetic stirring (EMS) on the quantities of the martensite stainless steel ingots was investigated by static casting experiment. The results of the experiment show that to compared with the traditional cast, the EMS can obviously improve the quantities of the martensite stainless steel ingots. By the EMS technique, the ratio of equiaxed grains greatly increased and when the current remains content, the ratio of equiaxed grain increases first and then decreases as the stirring frequency increasing. There is a maximum value at the 5Hz. With the EMS the carbon and the chromium in the ingots are better distributed. The segregation of C and Cr is inhabited. And also with the EMS, the grains of the martensite stainless steel ingots become finer and more homogeneity; consequently the appearance and distribution of the troostite in the ingots obviously changed: without the EMS the troostite distributes in net shape or block shape and with the EMS, the troostite distributes in the matrix dispersedly.

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Effect of Heat Treatments on Microstructure of Rapidly Solidified TiCo Ribbons

MRS Proceedings ◽

10.1557/proc-842-s1.5 ◽

2004 ◽

Vol 842 ◽

Author(s):

Kyosuke Yoshimi ◽

Akira Yamauchi ◽

Ryusuke Nakamura ◽

Sadahiro Tsurekawa ◽

Shuji Hanada

Keyword(s):

Crystal Structure ◽

Dislocation Density ◽

Grain Growth ◽

Heat Treatments ◽

Grain Structure ◽

Second Phase ◽

Burgers Vector ◽

Rapidly Solidified ◽

Equiaxed Grain ◽

Observation Results

ABSTRACTThe effect of heat treatments (aging or annealing) on microstructure was investigated for rapidly solidified ribbons of near-stoichiometric TiCo. In as-spun ribbons, it was observed by TEM that an equiaxed grain structure was developed and its crystal structure had been already B2-ordered, while a small amount of a second phase, Ti2Co, finely disperses in grains and along grain boundaries. Some grains were dislocation-free but others contained curved or helical dislocations and prismatic loops having a Burgers vector parallel to <100> directions. By annealing the as-spun ribbons at 700°C for 24h, the dislocation density was obviously increased compared with that of the as-spun ribbons, while grain growth appears to occur slightly. The increase of the dislocation density in the annealed ribbons is believed to result from the condensation and/or absorption of supersaturated vacancies. Therefore, the TEM observation results indicate that a large amount of supersaturated thermal vacancies were retained in the TiCo ribbons by the rapid solidification.

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