Mechanical Behaviour of Titanium, Ti-6Al-4V (wt %) Alloy and Ti-47Al-2Cr (at %) Alloy Produced Using Powder Compact Forging

Abstract

Powder compact forging was used to produce bulk consolidated titanium and Ti-6Al-4V (wt %) and Ti-47Al-2Cr (at%) alloy disks from hydrogenated and dehydrogenated (HDH) and gas atomised powders (GA) powders (in the case of titanium and Ti-6Al-4V) and a mechanically milled powder (in the case of Ti-47Al-2Cr alloy). The bulk titanium and Ti-6Al-4V (wt %) alloy have been produced by forging of the powder compacts. The Ti-47Al-2Cr (at %) alloy was produced using canned powder compact forging of a Ti/Al/Cr composite powder. The purpose of the present study is to investigate the deformation and fracture behaviour of the bulk consolidated as-forged materials, by conducting tensile testing at room temperature (RT) and examination of the fractured specimens which had near-α, α + β and  phase structures, respectively. It was found that as-forged bulk titanium disk produced using HDH powder showed a yield point with a yield strength of ~700 MPa and with a considerable amount of ductility. While the as-forged Ti-6Al-4V (wt %) alloy produced using HDH powder, fractured prematurely without any yielding. On the other hand yielding was observed in the as-forged Ti-6Al-4V (wt %) alloy produced using GA powder, showing a yield strength of ~970 MPa and a considerable amount of plastic strain to fracture. The bulk consolidated Ti-47Al-2Cr (at %) alloy also fractured prematurely with fracture strength of ~125 MPa. The mechanical behaviour of the as-forged bulk materials was found to be dependent on several factors such as initial powders used, green density of the powder compact, forging parameters used during forging. It was expected that the entrapped gas in green compacts, absorbed oxygen, porosity and inter-particle bonding play an important role on the quality of the as-forged material, which in turn affected the mechanical behaviour of the bulk material.

Cost Effective Forging of Titanium Alloy Parts and their Mechanical Properties

“…Induction heating is a well-tried way of achieving rapid heating and has been used successfully in ferrous PM [10,11]. More recently, induction heating has been successfully used in titanium PM for sintering prior to forging [12,13] and for heating prior to forging in air [14].…”

Thermomechanical Consolidation of Ti/Al/Cr Composite (Composition: Ti-47Al-2Cr (at %)) Powders

“…The parameters used for tensile testing of the HIP and powder forged samples are also given in our previous papers [4,5], the high temperature (HT) tensile testing of the powder forged samples was done on the specimens having a gauge length of 8.5mm, with a strain rate of 1.88x10 -4 /sec. Scanning electron microscopy (SEM), X ray diffractometry (XRD), and optical microscopy techniques were used for the microstructural characterization of the samples.…”

The Tensile Mechanical Properties of Thermomechanically Consolidated Titanium at Different Strain Rates

“…Khan et al [11] used high velocity powder compacting technique to compact Ti-6Al-4V (wt pct) alloy powder and found that with a high ram velocity, a relative high density of~86 pct can be achieved. Thermomechanical powder consolidation techniques such as hot isostatic pressing (HIP), [12,13] powder compact forging (PCF) [14][15][16] , and powder compact extrusion (PCE) [17] have been used by several research groups to consolidate titanium/titanium alloy powders and titanium/alloying element/master alloy powder blends. These works showed clearly that such powder consolidation processes can achieve good mechanical properties which are comparable to those of ingot metallurgy titanium/titanium alloys with same compositions.…”