Fabrication Of Titanium Alloys Research Articles

Recent Development of Low-Cost β-Ti Alloys for Biomedical Applications: A Review

The necessity for biomedical components is increasing every year. However, Ti6Al4V, the most widely utilized titanium alloy for biomedical implants are very costly owing to the high price of V alloying element. Furthermore, both alloying elements Al and V, have adverse effects in human body which is not desirable. This review paper highlights significant findings on alloy design using low-cost alloying elements, their processing routes, and their relationship to microstructural, mechanical, and biological properties. Mo, Fe, Mn, Zr, and Cu were identified as low-cost alloying elements and fabrication of titanium alloys with these elements are usually carried out using arc melting, investment casting, powder metallurgy, additive manufacturing, diffusion couple, and thermomechanical processing. Several processing routes can be chosen to obtain optimum properties such as β-phase titanium alloy structure, low elastic modulus, and high strength. Alloy design, post-heat treatment process, and fatigue test for newly developed alloys are research that can be carried out in the future for the development of new titanium materials that are safe for human use and at a more affordable price.

Influences of residual stress and micro-deformation on microstructures and mechanical properties for Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy produced by laser powder bed fusion

Laser powder bed fusion (LPBF) yields unique advantages during the fabrication of titanium alloys. In the present work, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy specimens with excellent mechanical performances were fabricated by LPBF. The as-built specimens displayed relatively high strength and ductility under modest volume energy densities (VEDs), whereas they manifested high strength with low ductility under high VEDs. To investigate the key reason of this phenomenon, the specimens were designed with two VEDs ranges of 60 J/mm3 and 85 J/mm3. Special attention was paid to the influences of residual stress and micro-deformation on microstructures and mechanical properties for the first time. The results indicated that the residual stresses and relative density of the 60 J/mm3 range specimens were higher than that of the 85 J/mm3 range specimens. Dislocation multiplication and dislocation movement promoted by the residual stress were hindered by the initial α' phase grain boundary (prior-α'GB), leading to the formation of α' metastable structures. The mean tensile strength and elongation of the 60 J/mm3 range specimens were 1248.1 MPa and 12.3 %, respectively, whereas the corresponding values for the 85 J/mm3 range specimens were 1405.3 MPa, 5.0 %, respectively. During deformation, the strength and ductility of the specimens were first improved by lamellar structures generated from prior-α' phases, and then effectively enhanced by the interaction between the {10–12} twins and dislocations. However, pores significantly reduced the ductility; hence, high VED specimens with large twins and numerous large pores increased the strength and reduce the ductility.

Fabrication of Titanium alloy by Electromagnetic Continuous Casting (EMCC) Method for Medical Applications

Fabrication of Titanium alloy by Electromagnetic Continuous Casting (EMCC) Method for Medical Applications

Processing and Characterization of Ti-6Al-4V Samples Manufactured by Selective Laser Melting

Titanium and its alloys are well known as one of the best in-vitro and in-vivo bone replacement metallic biomaterial due to its excellent balance between biomechanical and biofunctional properties. The selective laser melting (SLM) method has a lower cost and shorter manufacturing time than the conventional routes used in the fabrication of titanium alloys. In this work, Ti6Al4V sheets were manufactured by SLM (LM samples) and subsequently annealed for stress relief at 750 oC for 10 min (LM-A samples). SEM, XRD and contact profilometry measurements were carried out to characterize the elemental composition, phases and surface morphology of different samples. A micro-tribo-mechanical evaluation was also performed by micro-indentation and scratch tests. The resulting surface was rough (Ra = 9.1 ± 0.5 μm) for all samples, showing protuberances with spherical morphology. For annealed samples, an oxide layer composed of rutile and Al2O3 was observed that increased the micro-hardness of the surface in LM-A sheets. However, after removing this oxide layer, the micro-hardness of the LM-A sheets was reduced when compared to LM samples as a result of the stress relief. A direct relationship between Vickers micro-hardness and scratch resistance was always observed. Therefore, LM-A sheets showed higher scratch resistance at low loads (oxidized surface effect) than LM samples, but lower resistance at high loads (bulk effect).

OS2133 3D造形したチタン合金の平面曲げ疲労特性に及ぼす表面改質の影響

OS2133 3D造形したチタン合金の平面曲げ疲労特性に及ぼす表面改質の影響

Wire electrochemical machining with axial electrolyte flushing for titanium alloy

Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining (WECM) is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy (TC1). The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.

Resistance Heated Pressing (RHP): A Novel Technique for Fabrication of Titanium Alloys

A novel powder metallurgical technique for the fabrication of titanium alloys has been developed by utilizing a pressure-assisted, resistance-heating sintering technique. In this technique, the high electrical resistance of oxide layers present on the surface of powder particles has been exploited to ensure effective resistance heating of green compacts. Ti-6Al-4V pre-alloyed powders of 100 µm size were compressed while being heated under a variety of conditions of sintering temperature, pressure and time. The outcomes of our experiments have proven that resistance heating can be a very effective means of heating during powder consolidation. The results have indicated that the required sintering time and temperature in the new resistance-heated sintering technique are much reduced in compared to sinter-press and/or hot isostatic pressing techniques, resulting in a refined microstructure with a concomitant improvement in mechanical properties.