Investigation of Fine-scaled Alpha Precipitation in the Modeled Ti-Mo and Ti-Mo-Al Alloys
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Authors
Munna, Ahsan Habib
Issue Date
2023
Type
Thesis
Language
Keywords
Alternative Title
Abstract
Due to their remarkable physical and mechanical characteristics, ? titanium alloys are becoming more and more significant in the domains of chemical industry, aerospace, and biomedical materials. The size scale, distribution, and volume fraction of the precipitated phase in the parent phase matrix are all significant elements of these alloys' microstructure that have an impact on their performance. Therefore, a comprehensive understanding of microstructural evolution in ? titanium alloys upon various thermal and/or mechanical processes is essential for improving their performance.The primary objective of this research is to promote the activation of various non-classical nucleation mechanisms, specially pseudospinodal decomposition mechanism and ω-assisted ⍺ nucleation mechanism, via carefully designing various heat-treatment conditions in the binary Ti-Mo and ternary Ti-Mo-Al alloys. We concentrate on the binary Ti-18Mo (wt%) and ternary Ti-18Mo-5Al (wt%) alloys in particular. Controlled heat treatments enable us to achieve fine-scaled ⍺ precipitation at the grain boundary and in the interior of grains by activating either pseudospinodal decomposition mechanism or ω-assisted ⍺ nucleation mechanism. Additionally, it can be observed that the mechanical properties are significantly influenced by the size scale and distribution of ⍺ precipitates via ⍺ precipitation hardening. The pseudospinodal decomposition mechanism is significantly influenced by the addition of an ⍺ stabilizer (Al), which significantly enhances the microhardness characteristics. Sophisticated electron microscopy methods, such as Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB), in conjunction with machine learning-based stereological analysis methods for microstructural quantification to study these microstructural traits. This enables us to characterize and investigate how heat treatment affects the development of alpha precipitates' microstructure. In summary, this study investigates the non-classical nucleation mechanisms for the characteristic ?-Ti alloys systems to evaluate the universality of these mechanisms for more complex ?-Ti alloy systems. The use of advanced electron microscopy techniques and machine learning-based stereological analysis enables us to understand the underlying mechanisms and factors influencing these mechanisms. The insights gained from this study will aid in the development of more complex ?-titanium alloys for industrial applications