Gradient Structures in Thin‐Walled Metallic Tubes Produced by Continuous High Pressure Tube Shearing Process

Abstract

A new severe plastic deformation process, the authors refer to as High Pressure Tube Shearing (HPTS), is proposed. This type of deformation processing enhances the strength of the walls of metallic tubes by producing gradient microstructures with ultrafine grained layers in near-surface regions. The thickness of the layers associated with a gradient in microstructure can be controlled by tuning the rotational and translational speeds of the process. The paper describes several examples of steel and titanium tubes processed by different variants of HPTS. The possibility of producing gradient microstructures with ultrafine grained layers at inner or outer surface of a tube, or at both surfaces is demonstrated by in-depth theoretical analysis, finite element simulations, and experimental investigation of the microstructure and texture of tube walls.

Analytical and numerical approaches to modelling severe plastic deformation

“…A successful exercise in analytical modelling of an axisymmetric forward spiral extrusion process [485] -yet another recent variety of SPD processingemployed an upper bound approach, developed earlier in the context of twist extrusion modelling [486]. Substantial efforts were also put in design and simulation of SPD processing of thin products [487,488], notably thin-walled tubes [315,489,490]. A process dubbed tube channel pressing [491] was studied by Farshidi and Kazeminezhad [492] by employing FEM simulations.…”

The Role of Mandrel Rotation during CSET Processing Demonstrated on a 3003 Aluminium Alloy

“…In both methods, high hydrostatic pressure is applied on a tube positioned between inner and outer mandrels, each of which may rotate independently thus evoking shear deformation of the tube wall. Similarly, in the high-pressure tube shearing (HPTS) process, a tube has been drawn through a rotating die, and an internal rotating mandrel causes thinning of the tube wall [16]. Rotation and high hydrostatic pressure resulted in local shear deformation which resulted in a fine-grained and frequently gradient microstructure.…”

Microstructural Evolution of a 3003 Based Aluminium Alloy during the CSET Process

“…However, as these methods deform the whole volume of the body, there is a serious length limitation of samples. This length restriction was overcome in high pressure tube shearing (HPTS) method, where the main deformation zone was limited [ 13 ]. During HPTS, the tubular sample is drawn through a rotating die, whereas the wall thickness of the tube is reduced by an internal rotating mandrel.…”

“…During HPTS, the tubular sample is drawn through a rotating die, whereas the wall thickness of the tube is reduced by an internal rotating mandrel. The shear deformation due to the rotation and high local hydrostatic pressure lead to fine grain size and gradient microstructure [ 13 ]. These methods generally combine several press steps for an incremental straining to achieve the required strength level.…”