Fabrication of an Ultra-Fine Grained Pure Titanium with High Strength and Good Ductility via ECAP plus Cold Rolling

Abstract

Microstructure evolutions and mechanical properties of a commercially pure titanium (CP-Ti, grade 2) during multi-pass rotary-die equal-channel angular pressing (RD-ECAP) and cold rolling (CR) were systematically investigated in this work, to achieve comprehensive property for faster industrial applications. The obtained results showed that the grain size of CP-Ti decreased from 80 µm of as-received stage to 500 nm and 310 nm after four passes and eight passes of ECAP, respectively. Moreover, abundant dislocations were observed in ECAP samples. After subsequent cold rolling, the grain size of ECAPed CP-Ti was further refined to 120 nm and 90 nm, suggesting a good refining effect by combination of ECAP and CR. XRD (X-ray diffractometer) analysis and TEM (transmission electron microscope) observations indicated that the dislocation density increased remarkably after subsequent CR processing. Room temperature tensile tests showed that CP-Ti after ECAP + CR exhibited the best combination of strength and ductility, with ultimate tensile strength and fracture strain reaching 920 MPa and 20%. The high strength of this deformed CP-Ti originated mainly from refined grains and high density of dislocations, while the good ductility could be attributed to the improved homogeneity of UFG (ultra-fine grained) microstructure. Thus, a high strength and ductility ultra-fine grained CP-Ti was successfully prepared via ECAP plus CR.

Development of a High Strength Mg-9Li Alloy via Multi-Pass ECAP and Post-Rolling

“…However, the addition of lithium to the magnesium alloy forming Mg-Li alloy results in the formation of a β-rich Li phase which greatly increases the dislocation slip system and improves the plastic deformation ability of the Mg-Li alloys [26]. The results obtained from the reported research [27,28] show that, the use of rolling technique leads to an improvement in the strength properties of the Mg-Li alloy, activate more slip systems, enhance the ability of intergranular co-opening and improve the ability of plastic deformation at room temperature (RT). In the rolling process, strong basal texture will be formed [29].…”

Development of High-Performance SiCp/Al-Si Composites by Equal Channel Angular Pressing

“…The PM samples were pressed for 0, 4 and 8 ECAP passes (marked as PM-0p-ECAP, PM-4p-ECAP and PM-8p-ECAP) with a velocity of 0.5 mm/s at 703 K. Prior to ECAP, cubic PM samples (20 mm × 20 mm × 40 mm) were put into the ECAP die, and they were held at 703 K for 15 min before pressing. This RD-ECAP procedure was proven to be very effective to obtain ultrafine-grained microstructure in several materials [33,34,[37][38][39]. Graphite was used as a lubricant to reduce the friction between the billet and the inner wall of the die.…”

“…The compaction pressure, which has a significant influence on the compactness and properties of the final composite [31], was chosen to be 305 MP, which gives rise to a large apparent density of 2.56-2.58 g cm −3 . Then, the cold pressed specimens buried by graphite were sintered in a furnace at 873 K for 4 h. Finally, the PM samples were processed using a home-made rotary die for ECAP (RD-ECAP) with 90 • channel intersection, the operation principle of which can be found in our earlier work [32][33][34][35][36]. The PM samples were pressed for 0, 4 and 8 ECAP passes (marked as PM-0p-ECAP, PM-4p-ECAP and PM-8p-ECAP) with a velocity of 0.5 mm/s at 703 K. Prior to ECAP, cubic PM samples (20 mm × 20 mm × 40 mm) were put into the ECAP die, and they were held at 703 K for 15 min before pressing.…”

Continuous Production of Pure Titanium with Ultrafine to Nanocrystalline Microstructure

“…Another method is to combine the SPD process with cold working. It has already been proven that the combination of processes can lead to even higher mechanical properties than in the case of purely SPD processing [20][21][22][23].…”

“…Another method is to combine the SPD process with cold working. It has already been proven that the combination of processes can lead to even higher mechanical properties than in the case of purely SPD processing [20][21][22][23]. This paper deals with the development of continuous technology for commercially pure titanium (titanium Grade 4) processing combining Conform SPD and rotary swaging leading to highstrength wire production.…”