Discovery via Integration of Experimentation and Modeling: Three Examples for Titanium Alloys

Abstract

One key aspect of any integrated computational materials engineering approach is the integration of experiments that provide critical information for the modeling activities. This article describes, using case studies, three examples of critical experiments that have been conducted in an integrated fashion with modeling activities for titanium alloys, providing valuable information in an accelerated manner. The first has been used to identify key microstructural features associated with fracture toughness in Ti-6Al-4V and integrates artificial neural networks and various experimental techniques. The second is associated with defect accumulation in highly constrained titanium structures and integrates a highly innovative characterization technique (precession electron diffraction) and dislocation dynamics. The third is a high-throughput combinatorial technique to understand the oxidation behavior of titanium alloys and couples the experimental effort with the CALPHAD approach. INTRODUCTIONThe composition, microstructure, and defect structures of advanced nonferrous structural alloys are the predominant factors that govern the response of the material to an externally applied stimulus. For example, there will be an elasticplastic response of the material to an externally applied load. Similarly, there will be a compositional and structural evolution in response to thermal excursions. Although these responses are expected to occur, the precise details of the responses are less well understood. integrated computational materials engineering (ICME), or integrated computational materials science and engineering (ICMSE), is a strategy to integrate knowledge, represented by both computation/simulation and high-fidelity experimental databases, from across the composition-microstructure-processing-property paradigm so as to engineer a solution to a design problem. ICME strategies are increasingly being put into service and adding value. 1-4 However, to be effective the individual components must accurately describe materials phenomena.For many structural materials, the precise details of materials response to external stimuli are not well understood. Often, an integrated experimental and computational approach can help elucidate these missing details. While not representing a complete ICME program, each of these integrated activities has provided knowledge that was otherwise lacking. Each of these programs is related to a different problem facing a particular class of nonferrous structural alloys-titanium-based alloys. These include efforts to understand the following: the influence of microstructure on the fracture toughness of a + b-processed Ti-6Al-4V, the influence of defect populations on performance of single-phase and two-phase titanium alloys, and the role of composition on the oxidation behavior of several titanium alloys. The motivation and details of each problem are described separately, as are the conclusions. It is seen that the integration of critical and careful experiments with various modeling schemes ca...

Development of strength-hardness relationships in additively manufactured titanium alloys

“…It is costly and impracticable during production to extract specimens from different locations and orientations in AM components to investigate how processing and design changes will impact the local mechanical properties. Microstructural and phase composition has also been used to predict the mechanical properties [22][23][24] and toughness [25] for Ti-6Al-4V components, but using these methods requires a detailed microstructural and chemistry composition analysis. In contrast, hardness measurements offer a fast and inexpensive method of measuring material properties at specific locations.…”

Characteristic study of cold sprayed N06601 superalloy surface

“…Corrosion of metals/alloys and its preventive measures costs around 4% of GDP of any developed economy, which has been translated to around $8billion annually to Australia and $250 billion to U.S.A [41]. The composition and microstructure properties like presence of pores, oxides, inclusions or any other structural defects are the important factors deciding the response of the base alloy or coating to an externally applied stimulus [42]. The better surface finish, high hardness, oxide-free and dense microstructure with low porosity has indicated the suitability of this newly developed cold sprayed coating for blocking the transfer of the aggressive environmental species (like in power plants, marine and aerospace environments), and secure the substrate from the exposure of harmful degrading elements.…”

“…This is to reduce the stresses generated because of mismatch in thermal expansion which results in failure of the coating during application in thermal cyclic conditions such as boilers and incinerators. The Cr 3 C 2 -based coating selected for this study has compatible thermal expansion coefficient of 10.3 × 10 −6 °C−1 (for Ni 12.8 × 10 −6 °C−1 and Fe 11.4 × 10 −6 °C−1 ) [41][42][43]. Carbides have high hardness and high melting point, and these properties are maintained at high temperature; therefore these are preferred for wear resistant applications in high-temperature conditions.…”

Characterization and Optimization of Ni-WC Composite Weld Matrix Deposited by Plasma-Transferred Arc Process

“…A more detailed explanation may be found elsewhere. [24] The critical microstructural feature is a special twist boundary, whereby adjacent equiaxed alpha particles have parallel (0001) planes (parallel to within a degree or two). A necessary condition is that the interface must also be parallel to the (0001) plane of both adjacent equiaxed alpha particles.…”

“…Thus, not all particles with parallel (0001) planes will experience microcracks, only The full extent of this research cannot be adequately presented in a single publication. The characterization activities (though published first [24] ) were extensively informed by this modeling effort. Indeed, without the identification of the importance of the size of the equiaxed alpha particle size, the characterization efforts would not have been pursued as carefully.…”