FLOW FORMING OF AEROENGINEMATERIALS

Abstract

Flow forming is a fairly new technique used for the production of dimensionallyaccurate near net shaped hollow components. The process has many advantagessuch as cost effectiveness and eliminating further operations like welding, machin-ing, etc. This study focuses on the characterization of flow formed componentsto understand the process. Flow formed components are composed of differentreductions and characterization techniques are applied to reveal the resulting mi-crostructural differences. Effect of number the of passes on the material is alsoinvestigated.Metallographic analysis was conducted by optical microscope, electron mi-cro probe analyser (EPMA) and the electron back scatter diffraction technique(EBSD) in a scanning electron microscope (SEM). Texture evolution of the sam-ples was examined either by laboratory x-ray diffraction or EBSD technique.Furthermore, residual stresses were measured by neutron diffraction (at StrainAnalyzer for Large and Small Scale Engineering Applications (SALSA) and PulseOverlap Diffractometer (POLDI) instruments), laboratory x-ray diffraction andhole drilling. Stress relief heat treatments were carried out at 500C for either 4or 16 hours to mitigate residual stresses without losing much of the strength.The experiments conducted show that flow forming is a process resulting inheterogeneous microstructure with grains elongated along the deformation direc-tion. Texture evolution is different from the typical rolling of steels with bodycentred cubic crystal structure. Any significant effect of the number of passeswas not observed.Due to the nature of the process, residual stresses in the axial and hoop direc-tions are critical. Therefore, stress distributions through thickness of the samplesare plotted. It is observed that in the thick section, the stresses are higher. Heattreatments applied at 500C for 4 or 16 hours are effective in diminishing thestresses.

Date of Award	31 Dec 2014
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Michael Preuss (Supervisor)