Cost Effective Forging of Titanium Alloy Parts and their Mechanical Properties

Abstract

Both open die and closed die powder compact forging can be used for the consolidation of Ti and pre-alloyed Ti 6Al 4V powders produced by a hydride-dehydride (HDH) process. The approach used is initial cold or warm compaction into cylindrical shapes, or into a specific pre-form shape appropriate for achieving a particular final forged shape. The economic benefit is near net-shape processing with minimum machining required after forging. Manufacturing costs are also minimised by forging a compact, with a sufficiently high enough density, in air, without a protective atmosphere. The challenge, from a manufacturing point of view, is the operation of a manufacturing route which gives rapid and qualified compaction to meet production demands and batch sintering to achieve a high enough density prior to final forging to shape. In addition to this the final product has to have the right level of mechanical properties. This paper reviews some key findings from powder compact production, through to sintering and forging. These will be presented in terms of alpha-beta phase distribution in the microstructure, the degree of porosity, heat treatment and their effects on mechanical properties.

Processing, microstructure, properties and fracture behaviour of Ti–6Al–4V manufactured from pre-alloyed powder

“…The tensile data measured from as-extruded rod (CIP + VS + HP + Extruded in Figure 10) show further enhancement of the material performance under uniaxial loading and here YS, UTS and failure strain values of 971, 1152 MPa and 9-11%, respectively were obtained. In reference to previously published tensile data on PM or ingot Ti-6Al-4V alloy, the level of strength attained in this study for as-extruded material is relatively higher, whereas ductility is lower [4,6,7,[16][17][18]. El-Soudani et al have reported that consolidation of blended Ti-6Al-4V powders through can-less extrusion can provide average YS and UTS in the range 875-926 MPa and 979-1021 MPa respectively, while ductility of the material varies between 13% and 15.4%.…”

“…It is suspected that if the as-sintered billet had been directly induction heated in air prior to extrusion, it would have picked up a significant amount of impurity oxygen due to the presence of many open pores. As a guideline, a compact with a relative density greater than 92% of full density (and one which contains pores in the form of closed porosity) results in minimal oxygen pick-up during final consolidation in air [7]. This means that in the future, relatively high open porosity of the as-vacuum sintered Cold isostatic pressed billets might be a potential issue which requires further in-depth attention, particularly if larger billets are to be produced by Cold isostatic pressing pre-alloyed powders.…”

“…Besides the economic benefit, PM can produce complex shaped parts with a high degree of freedom in the selection of alloy composition and with uniform microstructural characteristics [3-6]. A number of powder processing methods have been developed including thermomechanical powder consolidation (TPC) processes, such as powder extrusion, powder forging or powder rolling to derive benefits of both traditional PM and conventional extrusion, forging or rolling technology while potentially maintaining cost effectiveness [7,8].…”

Processing, Microstructures and Properties of a Ti-6Al-4V Extrusion Produced by an Industrial Scale Setup

“…variations in YS, UTS along and ductility. Overall tensile property data presented here is either similar or inferior compared to the data reported in literature before[4,7,8,13,14] .…”

“…The restrictions on the use of titanium for more general engineering applications, because of its high cost, is well known and requires no further comment [1][2][3]. Thermomechanical powder consolidation (TPC) processes, such as powder compact extrusion (PCE), are capable of costeffectively producing near fully dense material with a wide range of compositions, microstructures and properties [4][5][6][7][8]. PCE combines traditional powder metallurgy and conventional extrusion technology along with the derived benefits of both processes.…”