Mapping of femtosecond laser-induced collateral damage by electron backscatter diffraction

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98720/1/JApplPhys_110_083114.pd

Nickel-Based Superalloys for Advanced Turbine Engines: Chemistry, Microstructure and Properties

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77223/1/AIAA-18239-462.pd

A Numerical Method for Sharp-Interface Simulations of Multicomponent Alloy Solidification

We present a computational method for the simulation of the solidification of multicomponent alloys in the sharp-interface limit. Contrary to the case of binary alloys where a fixed point iteration is adequate, we hereby propose a Newton-type approach to solve the non-linear system of coupled PDEs arising from the time discretization of the governing equations, allowing for the first time sharp-interface simulations of the multialloy solidification. A combination of spatially adaptive quadtree grids, Level-Set Method, and sharp-interface numerical methods for imposing boundary conditions is used to accurately and efficiently resolve the complex behavior of the solidification front. The convergence behavior of the Newton-type iteration is theoretically analyzed in a one-dimensional setting and further investigated numerically in multiple spatial dimensions. We validate the overall computational method on the case of axisymmetric radial solidification admitting an analytical solution and show that the overall method's accuracy is close to second order. Finally, we perform numerical experiments for the directional solidification of a Co-Al-W ternary alloy with a phase diagram obtained from the PANDAT database and analyze the solutal segregation dependence on the processing conditions and alloy properties

Ruthenium Aluminides: Deformation Mechanisms and Substructure Development

Structural and functional materials that can operate in severe, high temperature environments are key to the operation of a wide range of energy generation systems. Because continued improvements in the energy efficiency of these systems is critical, the need for new materials with higher temperature capabilities is inevitable. Intermetallic compounds, with strong bonding and generally high melting points offer this possibility for a broad array of components such as coatings, electrode materials, actuators and/or structural elements. RuAl is a very unusual intermetallic compound among the large number of B2compounds that have been identified and investigated to date. This material has a very high melting temperature of 2050?C, low thermal expansion, high thermal conductivity and good corrosion resistance. Unlike most other high temperature B2 intermetallics, RuAl possesses good intrinsic deformability at low temperatures. In this program fundamental aspects of low and high temperature mechanical properties and deformation mechanisms in binary and higher order RuAl-based systems have been investigated. Alloying additions of interest included platinum, boron and niobium. Additionally, preliminary studies on high temperature oxidation behavior of these materials have been conducted

High-Temperature Performance of Actively Cooled Vapor Phase Strengthened Nickel-Based Thermostructural Panels

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90639/1/AIAA-53998-163.pd

Sustained peak low-cycle fatigue: The role of oxidation resistant bond coatings

Important developments in turbine blade technology, including cast thin-walled airfoils with complex internal cooling passes, place significant thermal gradients and stresses on the multilayered coating systems used to thermally insulate the blade from the hot combustion gases. As gas turbine engine operating temperatures increase, the intermetallic bond coatings traditionally used in thermal barrier coating systems undergo increased creep deformation. Bond coats for single crystal turbine blades have been designed primarily for oxidation protection with minimal consideration of mechanical and microstructural optimization. At higher temperatures, intrinsic failure mechanisms of coatings such as rumpling and cracking due to sustained peak low-cycle fatigue (SPLCF), limit the lifetimes of engine blades [1]. Bond coatings have been shown to extend or reduce the SPLCF lifetime of a specimen as compared to uncoated single crystals. The mechanical and microstructural properties bond coatings and their oxides that impact fatigue crack propagation rates have been investigated. Please click Additional Files below to see the full abstract

Oxide‐Assisted Degradation of Ni‐Base Single Crystals During Cyclic Loading: the Role of Coatings

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87025/1/jace4578.pd