Anisotropy of the fracture toughness of structurally inhomogeneous ageing alloys

Abstract

The dependence of the fracture toughness K 1C of rolled ageing alloys with structural and crystallographic textures on the loading direction is established. A formula describing the anisotropy of the K 1C and including structural parameters of structurally textured alloys on planes of growth of mode I cracks is derived and validated for aluminum alloys. The influence of crystallographic planes and crack growth direction on K 1C is analyzed for titanium alloy as a rolled material with crystallographic texture Introduction. The anisotropy of strength, plasticity, and crack resistance of structural materials caused by deformation (rolling, forging, forming, etc.) and hardening heat-treatment is studied in [1,2,[5][6][7][8]. Such thermomechanical actions are widely used in forming structural elements for modern engineering. Of importance is to optimize the thermomechanical conditions that would provide the necessary anisotropy of the crack resistance of the material, which would enhance the operational reliability of structures.The research in the field may be developed by establishing the dependence of the anisotropy of the crack resistance of structural alloys on their structural inhomogeneity at the meso-, micro-, and nano-levels, including structural and crystallographic texture [1,5,15]. These types of structural inhomogeneity often appear simultaneously but have different effects on the anisotropy of crack resistance under thermomechanical loads. The structural texture of ageing alloys represents directional changes in the shape, dimensions, and orientation of grains and subgrains of the matrix phases and in the distribution density of disperse particles of the hardening phases on the crack growth planes. This determines the direction of structural embrittlement. The crystallographic texture represents the preferential orientation of crystallites, restricting the number of active slip planes in certain crack growth directions and, therefore, the capability of the material to form plastic zones at the crack tip in these directions, which reduces crack resistance [3,4]. The effect of the crystallographic texture on the anisotropy of crack resistance is much stronger in metals with a hexagonal close-packed (HCP) lattice. Such a lattice has much less active slip systems compared with the face-centered (FCC) and body-centered (BCC) cubic lattices [13].The influence of these types of structural inhomogeneity on the anisotropy of crack resistance is poorly understood. This is why it is impossible to establish the general pattern of its manifestation considering that structural alloys have many phases and their matrix phases have lattices of different types.The present paper examines the individual effects of the structural and crystallographic textures (caused by rolling and heat treatment) of ageing alloys on the anisotropy of crack resistance.1. Influence of Structural Texture on the Anisotropy of Fracture Toughness. We will develop and experimentally validate a structural mechanical approach to evaluating and predi...

Studies on strain-hardening models for structural steels at a directed reduction in sizes of their structural elements

“…For the pipes from austenitic steel, the true strain e = -( ) F F F Procedures of Structural Investigations. Complex investigations of the structure and phase composition of austenitic steels were carried out by light and electron microscopies on MIM-8 and UEMV-100K microscopes and by X-ray analysis on DRON-2.0 and URS-55 units in FeK a radiation using procedures [4,[16][17][18][19].…”