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

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

The influence of stacking fault energies and solute segregation on high temperature creep strength in L12-containing Co-based Superalloys

Co-based superalloys strengthened by the γ’-(L12) phase exhibit comparable and, in some cases, superior high temperature creep resistance to 1st-generation Ni-based superalloys. Despite the comparable creep resistance between Co- and Ni-based superalloys, the high temperature creep deformation modes are markedly different: the γ’ phase in Ni-based superalloys is typically sheared via coupled a/2\u3c110\u3e matrix dislocations, whereas the γ’ phase in Co-based superalloys is sheared via Shockley superpartial a/3\u3c112\u3e dislocations, which leave superlattice intrinsic stacking faults (SISF) behind in their wake. Previous investigations have shown that the creep strength of Co-based alloys increases with increasing SISF energy. In this contribution, the SISF energies for Co3(Al,W,X) and Co3(Al,Mo,X) compounds (X = Cr, Ta, Ti, Nb, and V) are calculated using density functional theory and special quasi-random structures (SQS) in order to assess the potency for quaternary alloying additions to increase the SISF energy, and thus the high temperature creep strength. In all alloy systems except Co-Al-W-Ti, quaternary compositions exhibited higher SISF energies compared to binary or ternary compositions. This implies that higher-order alloying additions that partition to the γ’ phase will always aid to increase the SISF energy and the high temperature creep strength as well. Recent work incorporating vibrational entropy in order to determine temperature-dependent SISF energies will be presented. Additionally, recent observations via high resolution microscopy and atom probe tomography of solute segregation at the SISFs will be presented. The relationship between solute segregation, SISF energy, and high temperature creep strength will be exemplified. Please click Additional Files below to see the full abstract