The α and prior β textures and microtextures of a lamellar Ti6242 forged disk were characterized by advanced electron back scattered diffraction (EBSD) and related to crystallographic features of faceted crack initiation sites of dwell fatigue specimens tested along the radial direction (RD). Large feather-like structures of α colonies with close orientations were observed at boundaries of elongated prior β grains. Their orientation belongs to the <11-20>α//z fiber, aligning the c-axis in RDs (z: axial direction of the disk). They are inherited from prior β grains belonging to the major <100>β and minor <111>β//z fibers. These feather-like structures are strong regions of the forging that act as a preferential crack initiation site. Adjacent to them, one can observe large colony with evidence of prismatic slip. Thus, the facet formation seems triggered by stress redistribution from “weak” to “strong” regions due to the elastic and plastic anisotropy. Finally, the occurrence of neighboring β grains able to share close oriented feather-like colonies is discussed considering the reconstructed β microtexture and texture. This study may be helpful for further texture control during the forging process.
The low energy high current pulse electron beam (LEHCPEB) irradiation induces ultra fast dynamic temperature fields in the surface of the material to which is associated dynamic stress fields that causes intense deformation at the material surface and sub-surface. Improved surface properties (hardness, corrosion resistance) can be obtained using the LEHCPEB treatment. Under the “Melting” mode, the top surface (few µm) which is melted and rapidly solidified (107 K/s), can solidify has nano-domains formed from the highly under-cooled melt. The thermal stress wave that propagates in the sub-surface imposes strain hardening and grain size refinement. This induces a sub-surface hardening that can extent over about 100 µm. The use of the “Heating” mode is less conventional. This mode can promote grain size refinement, hardening as well as texture modification without modification of the sample geometry.
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