In:
Metallurgical and Materials Transactions A, Springer Science and Business Media LLC, Vol. 51, No. 8 ( 2020-08), p. 3967-3980
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.
Type of Medium:
Online Resource
ISSN:
1073-5623
,
1543-1940
DOI:
10.1007/s11661-020-05810-4
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2020
detail.hit.zdb_id:
1179415-X
detail.hit.zdb_id:
2037517-7
detail.hit.zdb_id:
192156-3
SSG:
19,1
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