Browsing by Author "Peel, MJ"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Dynamic recovery and recrystallization during hot-working in an advanced TiAl alloy
    (Carl Hanser Verlag, 2011-01-01) Schmoelzer, T; Liss, KD; Rester, M; Yan, K; Stark, A; Reid, M; Peel, MJ; Clemens, H
    Intermetallic TiAl alloys are light-weight high-temperature materials and intended to partly replace Ni based alloys in jet engines. Due to difficult forming operations, component prices are high and limit the possible field of application. During hot-working, recovery and recrystallization effects determine the microstructural evolution and thereby the mechanical properties of the finished part as well as its behavior during deformation. To study the occurring experiments with high-energy X-rays were conducted. By means of this method, the dominating processes were identified. The results were validated through electron back scatter diffraction experiments. © 2011 CARL HANSER VERLAG
  • No Thumbnail Available
    Item
    In situ study of dynamic recrystallization and hot deformation behavior of a multiphase titanium aluminide alloy
    (American Institute of Physics, 2009-12-01) Liss, KD; Schmoelzer, T; Yan, K; Reid, M; Peel, MJ; Dippenaar, RJ; Clemens, H
    Hot-compression tests were conducted in a high-energy synchrotron x-ray beam to study in situ and in real time microstructural changes in the bulk of a beta-solidifying titanium aluminide alloy. The occupancy and spottiness of the diffraction rings have been evaluated in order to access grain growth and refinement, orientation relationships, subgrain formation, dynamic recovery, and dynamic recrystallization, as well as phase transformations. This method has been applied to an alloy consisting of two coexisting phases at high temperature and it was found that the bcc beta-phase recrystallizes dynamically, much faster than the hcp alpha-phase, which deforms predominantly through crystallographic slip underpinned by a dynamic recovery process with only a small component of dynamic recrystallization. The two phases deform to a very large extent independently from each other. The rapid recrystallization dynamics of the beta-phase combined with the easy and isotropic slip characteristics of the bcc structure explain the excellent deformation behavior of the material, while the presence of two phases effectively suppresses grain growth. © 2009, American Institute of Physics
  • No Thumbnail Available
    Item
    An in-situ high-energy X-ray diffraction study on the hot-deformation behavior of a β-phase containing TiAl alloy
    (Elsevier Science Ltd., 2013-08-01) Schmoelzer, T; Liss, KD; Kirchlechner, C; Mayer, S; Stark, A; Peel, MJ; Clemens, H
    In engineering materials, microstructural evolution during hot-working critically determines the properties of the finished part. Intermetallic TiAl alloys are no exception and numerous attempts have been made to improve their performance by subjecting them to harmonized hot-working steps. In the current work a novel in-situ diffraction technique along with conventional microscopic methods were employed to characterize the behavior of the individual phases at two different deformation temperatures. A so-called TNM™ alloy with a nominal composition of Ti-43.5 Al-4 Nb-1 Mo-0.1 B (in at%), which exhibits an adjustable fraction of disordered β-phase at elevated temperatures, was deformed isothermally at 1220 °C and 1300 °C. At 1220 °C three phases (α,β,γ) are present in thermodynamic equilibrium which reduces to two (α,β) at 1300 °C. It was possible to observe in-situ the individual behavior of the involved phases during deformation and the phenomena which accommodate the defects generated by hot-working. Results of post-mortem microscopic investigations were used to confirm the findings. The results of the in-situ experiments give unique insights into the hot-deformation behavior of multi-phase TiAl alloys, which can be used for specific process optimization and for further alloy development. © 2013, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Residual stress measurements in a ferritic steel/In625 superalloy dissimilar metal weldment using neutron diffraction and deep-hole drilling
    (Elsevier Science Ltd., 2013-01-01) Skouras, A; Paradowska, AM; Peel, MJ; Flewitt, PEJ; Pavier, MJ
    This paper reports the use of non-invasive and semi-invasive techniques to measure the residual stresses in a large dissimilar weldment. This took the form of a butt weld between two sections of a P92 steel pipe, joined using an In625 welding consumable. Residual stress measurements have been carried out on the 30 mm thick welded pipe using the deep-hole drilling technique to characterise the through wall section residual stress distribution for the weld metal, HAZ and parent material. In addition, neutron diffraction measurements have been carried out within the weld zone. Diffraction patterns presented a high intensity and sharp peaks for the base P92 steel material. However measurements in the weld superalloy material were proven problematic as very weak diffraction patterns were observed. A thorough examination of the weld material suggested that the likely cause of this phenomenon was texture in the weld material created during the solidification phase of the welding procedure. This paper discusses the challenges in the execution and interpretation of the neutron diffraction results and demonstrates that realistic measurements of residual stresses can be achieved, in complex dissimilar metal weldments. © 2013, Elsevier Ltd.