Friction Stir Processing of Additively Manufactured Ti-6Al-4V Alloy: Structure Modification and Mechanical Properties

Abstract

This work explores the possibility of using friction stir processing to harden the Ti-6Al-4V titanium alloy material produced by wire-feed electron beam additive manufacturing. For this purpose, thin-walled workpieces of titanium alloy with a height of 30 cm were printed and, after preparation, processed with an FSW-tool made of heat-resistant nickel-based superalloy ZhS6U according to four modes. Studies have shown that the material structure and properties are sensitive to changes in the tool loading force. In contrast, the additive material’s processing direction, relative to the columnar grain growth direction, has no effect. It is shown that increasing the axial load leads to forming a 𝛽-transformed structure and deteriorates the material strength. At the same time, compared to the additive material, the ultimate tensile strength increase during friction stir processing can achieve 34–69%.

Regularities of Metal Transfer by Nickel-Based Superalloy Tool at Friction Stir Processing of Titanium Alloy, Produced by Wire Feed Electron Beam Additive Manufacturing

“…The workpieces in as-built condition had dimensions of 300 mm in height, 100 mm in length, and 6 mm in width. Before friction stir processing, 2.5 mm thick plates were cut out of these blanks by EDM-machine DK7750 (Suzhou Simos CNC Technology Co., Ltd., Suzhou, China) similar to the scheme presented in [17]. After that, friction stir processing was performed on a homemade friction stir welding machine using the following parameters: loading force 33.34 kN, tool travel speed 90 mm/min, and tool rotation rate 400 rpm.…”

“…Moreover, the properties of additive alloys in this case are significantly inferior to the required values [13]. In turn, friction stir processing, which allows modifying the structure of both the surface and the volume of the product due to dynamic recrystallization, can be used to locally improve the characteristics of additive parts and has already shown positive results both in the processing of aluminum alloys [14,15] and titanium alloys [16,17]. However, in the case of titanium alloys, the process of the stir zone formation by FSW/P and the peculiarities of material flow are still under-explored.…”

Friction Stir Welding/Processing of Various Metals with Working Tools of Different Materials and Its Peculiarities for Titanium Alloys: A Review

“…Additionally, friction stir processing is used to obtain workpieces for subsequent pressure forming using the effect of superplasticity [77]. The combined use of friction stirring processing and additive technologies makes it possible to obtain materials with different combinations of structure and functional characteristics, as well as to enhance structurally homogeneous and defect-free products obtained by 3D printing methods [78][79][80][81].…”

“…One of the present research directions is the application of friction stir welding or processing technologies to modify the structure and joining of products made of titanium alloys [17,[81][82][83][84][85][86]. Since titanium alloys have a high specific strength, heat resistance, and high corrosion resistance, they are widely used in various industries and medicine [87].…”

Microstructural Transformation and Enhanced Strength of Wire‐Feed Electron‐Beam Additive Manufactured Ti–6Al–4V Alloy Induced by High‐Pressure Torsion

“…The results herein may further serve as the basis for studies to improve the mechanical properties of 3D‐printed items of different geometry, using the SPD technique of friction stir processing, which, as is known, can be applied for surface treatment of various materials, including titanium alloys. [ 24–26 ]…”