Effect of autocatalysis on variant selection of α precipitates during phase transformation in Ti-6Al-4V alloy

• Published in: Computational materials science 2016-11, Vol.124, p.282-289
• Main Authors: Qiu, Di, Zhao, Pengyang, Shi, Rongpei, Wang, Yunzhi, Lu, Weijie
• Format: Article
• Language: English
• Subjects: Autocatalysis; Autocatalytic effect; Computer simulation; Elastic interaction; Materials science; Nucleation; Orientation; Phase field simulation; Precipitates; Precipitation; Titanium base alloys; Transformation texture
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2016.07.032

[Display omitted] •The precipitation of secondary α orientation variants near primary α lath is simulated.•The elastic interaction energy between primary and secondary precipitates is calculated.•A new mechanism is proposed for the formation of basketweave structure consisting of α variants. The elastic interactions among α precipitates and their effects on variant selection are investigated. The stress field around a semi-coherent α lath is first calculated using phase field microelasticity theory and then the precipitation process of β→α+β in Ti-6Al-4V is simulated using a 3-D phase field model. The orientations of secondary α variants induced by a primary (pre-existing) α variant obtained from the phase field simulations are consistent with those of variants within commonly observed α clusters in experiments. The formation of α/α orientation relationship of the [112¯0]α/60°-type, [10‾553]α/63.26°-type and [0001]α/10.53°-type frequently observed in experiments could be a direct consequence of autocatalysis during nucleation and growth of α variants. Moreover, the competition among α variants nucleated simultaneously around a primary α lath for limited number of preferred nucleation sites also results in the selection of variants possessing specific crystallographic orientation with respect to the primary α precipitates.