Verfestigung und Rekristallisation der Molybdänbasislegierung MHC bei ein- und mehrstufigen Umformprozessen

Translated title of the contribution: Hardening and recrystallization of the molybdenum based alloy MHC after single- and multi-step thermomechanical treatment

Maximilian Siller

Research output: ThesisDiploma Thesis

9 Downloads (Pure)

Abstract

The molybdenum-based alloy MHC, produced by powder metallurgy and exhibiting nominally 0.65 at.% Hf and 0.65 at.% C, shows promising high temperature properties. The excellent strength and creep resistance at elevated temperatures as well as the high recrystallization temperature are realized by the precipitation of nanometer-sized hafnium carbides in the course of a thermomechanical treatment. In this thesis the hardening and recrystallization behavior of MHC was characterized over a wide deformation and temperature range. For this purpose, two- and three-step deformation tests as well as scanning electron microscopy, transmission electron microscopy, hardness measurements, hot tensile tests and a chemical analysis, including atom probe tomography and electron beam microanalysis, were performed. The degree of deformation influences the interaction of precipitation, recovery and recrystallization during the thermomechanical treatment in various ways. The outcome of these interactions result in hardening or softening and it was shown that a strain higher than 40 \% leads to a lower hardening of the material. The analysis of complex thermomechanical processes, consisting of multiple deformations and heat treatments, showed that there is little influence of the precipitates on the deformed state of the material. Furthermore, the ductility in the room temperature tensile test was increased by recrystallization between the individual deformation steps. The outcome of this work provides relevant information for the thermomechanical processing of MHC and helps to implement innovative ways of thermomechanical processing.
Translated title of the contributionHardening and recrystallization of the molybdenum based alloy MHC after single- and multi-step thermomechanical treatment
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Clemens, Helmut, Supervisor (internal)
  • Schatte, Jürgen, Supervisor (external), External person
Award date16 Dec 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 06-12-2021

Keywords

  • molybdenum-hafnium-carbon alloy (MHC)
  • strain-induced precipitation
  • multi-stage deformation test
  • recovery
  • recrystallization
  • zener pinning
  • thermomechanical treatment

Cite this