Modelling the Competitive Growth of Primary, Allotriomorphic, and Secondary Alpha in Ti-6Al-4V

Ricardo Henrique Buzolin*, Desirée Weiß, Alfred Krumphals, Michael Lasnik, M. C. Poletti

*Korrespondierende/r Autor/in für diese Arbeit

Publikation: Beitrag in einer FachzeitschriftArtikel

Abstract

The competitive formation of allotriomorphic α along the prior β grain boundaries, secondary α-phase and the growth of globular primary α is described for the Ti-6Al-4V alloy during continuous cooling. The formation kinetics of the different morphologies of the α-phase is related to the nucleation rate of allotriomorphic α and secondary α as well as with the V supersaturation at the β matrix. A mesoscale physical model is developed for the allotriomorphic α and secondary α based on classical nucleation and growth of platelets. The growth of the primary α is modelled as the growth of a spherical particle embedded in a supersaturated β matrix. Continuous cooling tests at two different holding temperatures in the α+β field, 930 °C and 960 °C, and five different cooling rates, 10, 30, 40, 100 and 300 °C/minutes, are conducted. Additionally, interrupted tests are conducted at different temperatures to determine the progress of growth of primary α and formation of allotriomorphic and secondary α-phases during cooling. The size of primary α increases, while its circularity decreases with decreasing cooling rate. The area fractions of primary α decrease with increasing cooling rate and increasing holding temperature. Moreover, the lower the cooling rate, the thicker the plates of allotriomorphic α and secondary α. The growth of primary α, as well as the formation of allotriomorphic α plates is observed at the beginning of the cooling stage. The formation of secondary α occurs at last and is nearly negligible for very low cooling rates. The model is able to accurately predict the different α-phase formation behaviours and the obtained results show good agreement with the experimental ones.
Originalspracheenglisch
Seiten (von - bis)3967-3980
Seitenumfang14
FachzeitschriftMetallurgical and Materials Transactions / A
Jahrgang51
Ausgabenummer8
DOIs
PublikationsstatusVeröffentlicht - 1 Aug 2020

ASJC Scopus subject areas

  • !!Metals and Alloys
  • !!Materials Science (miscellaneous)

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