<p>To elucidate the cryogenic deformation behavior and its effect on microstructural evolution on the mechanical properties of titanium alloys, this study selects the Ti-6Cr-5Mo-5V-4Al (Ti6554) alloy as the research object, carrying out cryogenic tensile and impact tests, to obtain the stress strain curves and mechanical indicators and develop a modified Johnson Cook constitutive model. Scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) are utilized to analyze the morphological evolution, fracture mechanism, texture components, Schimidt factor (SF), and grain orientation spread (GOS). The results indicate that the {0001}&lt;11-20&gt; slip system remains activated for the <i>α</i> while these {110}&lt;111&gt;, {112}&lt;111&gt;, and {123}&lt;111&gt; systems remain the primary deforming components at lower temperatures. The increase of critical resolved shear stress (CRSS), extensive pile-up of dislocations, and geometrically necessary dislocations (GNDs) resulted from the inhomogeneous deformation can improve strength, while deterioration of ductility may be caused by the reduced number of activated slip systems and retarded dislocation mobility, incompatible deformation between the <i>α</i> and <i>β</i> phases, and dislocation accumulation and stress concentration. This work can provide a deep insight into understanding deformation behaviors and microstructural mechanism of Ti6554 alloy subjected to low-temperature tension.</p>

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Constitutive model and strengthening and ductility mechanisms of Ti6554 alloy with caliber rolled microstructure during cryogenic tension

  • Chuan Wu,
  • Chuan-Kun Liu,
  • Bao-Xi Liu

摘要

To elucidate the cryogenic deformation behavior and its effect on microstructural evolution on the mechanical properties of titanium alloys, this study selects the Ti-6Cr-5Mo-5V-4Al (Ti6554) alloy as the research object, carrying out cryogenic tensile and impact tests, to obtain the stress strain curves and mechanical indicators and develop a modified Johnson Cook constitutive model. Scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM) are utilized to analyze the morphological evolution, fracture mechanism, texture components, Schimidt factor (SF), and grain orientation spread (GOS). The results indicate that the {0001}<11-20> slip system remains activated for the α while these {110}<111>, {112}<111>, and {123}<111> systems remain the primary deforming components at lower temperatures. The increase of critical resolved shear stress (CRSS), extensive pile-up of dislocations, and geometrically necessary dislocations (GNDs) resulted from the inhomogeneous deformation can improve strength, while deterioration of ductility may be caused by the reduced number of activated slip systems and retarded dislocation mobility, incompatible deformation between the α and β phases, and dislocation accumulation and stress concentration. This work can provide a deep insight into understanding deformation behaviors and microstructural mechanism of Ti6554 alloy subjected to low-temperature tension.