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摘要
In near-isothermal local loading forming (NLLF) of large-size Ti-alloy parts, one of the challenging issues is to achieve accurately prediction of complex microstructural development. In this work, a thermo-mechanical-microstructural FE model considering complicated phase transformation and morphology transformation of the whole forming process is developed and experimentally verified. The simulated distribution of phase amount for primary alpha (alpha(p)) and secondary alpha (alpha(s)) phases agrees well with the experimental results. Based on the model, the evolution characteristics of alpha(p) phase, lamellar alpha(s) (alpha(ls)) phase, and globularized alpha s (alpha(gs)) phase for large-size Ti-alloy parts at different stages were investigated. It is found that alpha(s) phase amount in the first loading region is significantly higher than that in the second loading region, while alpha(gs) phase amount shows a reverse trend. Moreover, processing parameters including initial heating temperature, die loading speed, and loading pass greatly affect the relative amount and distribution uniformity of constituent phases among different loading regions. Finally, the formation mechanism of quasi-trimodal microstructures under NLLF of complex Ti-alloy parts is clarified by analyzing the coupling effects of applied deformation and phase transformation on the microstructure morphology. To achieve the regulation and control of the tri-modal microstructure, an optimized processing scheme is proposed.
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单位西北工业大学
