Microstructure and Mechanical Properties of Ti6Al4V Alloy Consolidated by Different Sintering Techniques (original) (raw)
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Journal of Materials Engineering and Performance
Ti-6Al-4V ingots with a nearly 100% density, fine and homogeneous basket-weave microstructure, and better comprehensive mechanical properties (UTS = 935 MPa, Y.S. = 865 MPa, El. = 15.8%), have been manufactured by vacuum pressureless sintering of blended elemental powders. Coarse TiH 2 powder, Al powder (2, 20 lm), V powder, and Al-V master alloy powder were used as raw materials to produce different powder mixtures (D 50 = 10 lm). Then, the compacts made by cold isostatic pressing were consolidated by different sintering curves. A detailed investigation of different as-sintered samples revealed that a higher density can be obtained by generating transient molten Al in the sintering process. Coarse Al powder and a rapid heating rate under the melting point of Al contribute to molten Al formation. The presence of temporary liquid phase changes the sintering mechanism, accelerating the sintering neck formation, improving sinterability of the powder mixtures. Density of 99.5% was achieved at 1150°C, which is markedly lower than the sintering temperatures reported for conventional blended elemental powder metallurgy routes. In addition, low interstitial content, especially for oxygen (0.17 wt.%), is obtained by strict process control.
IJERT-Synthesis and Characterization of Ti6Al4V Alloy by Powder Metallurgy
International Journal of Engineering Research and Technology (IJERT), 2013
https://www.ijert.org/synthesis-and-characterization-of-ti6al4v-alloy-by-powder-metallurgy https://www.ijert.org/research/synthesis-and-characterization-of-ti6al4v-alloy-by-powder-metallurgy-IJERTV2IS110888.pdf Experimental investigations were undertaken in order to understand the densification behavior and mechanical characterization of Ti6Al4V alloy by cold compaction operation. The preforms were prepared out of mixed elemental powders of Ti (90%), Al (6%), and V (4%) and compacted by 100 Ton hydraulic pressing machine with several designated loads of 22.5,28,30 and 32.5 tons, and the densities were calculated. Then the green compact having maximum density was immediately sintered in1800 c capacity High Temperature Tubular furnace with argon atmosphere up to 1250c with choking time of 2 hrs and followed by cooling to room temperature in the furnace itself. Alloy powder was characterized by scanning Electron Microscope and XRD and sintered Ti6Al4V was characterized by uniaxial compression test.
Influence of processing parameters on mechanical properties of Ti–6Al–4V alloy fabricated by MIM
Materials Science and Engineering: A, 2010
ABSTRACT This study presents the results of systematic variation of essential processing parameters with regard to thermal debinding and sintering of components fabricated by MIM using Ti–6Al–4V powder. The investigation aims at the understanding of the particular influence these parameters have on the mechanical properties of the sintered parts. This study shows that the debinding parameters appear to be rather uncritical, whereas sintering and cooling rates as well as maximum temperature are important in terms of their effect on tensile strength. Contrary to the strength, the ductility remains nearly unaffected. Based on these results, samples displaying yield strength of 757MPa, UTS of 861MPa and a plastic elongation of more than 14% were produced. These values meet the requirements of the ASTM B348-02 for titanium alloy grade 23.
The densification behavior of mixed Ti and Al/V master alloy powders for Ti-6Al-4V was investigated by a series of dilatometry tests to measure the shrinkage of the samples with the sintering temperature. The corresponding microstructural changes were examined under various sintering conditions with optical microscopy, energy-dispersive spectroscopy, and X-ray diffraction analyses. From these results, the consolidation of the mixed powders was divided into two domains: (i) sintering densification and solute homogenization of Ti and Al/V master alloy particles below 1293 K (1020 °C), and (ii) densification of Ti alloy phases above 1293 K (1020 °C). In the lower temperature region, the inter-diffusion between Ti and Al/V master alloy particles dominated the sintering of the mixed powders because the chemical gradient between two types of particles outweighed the surface energy reduction. Following chemical homog-enization, the densification induced the shrinkage of the Ti alloy phases to reduce their surface energies. These tendencies are also supported by the density and grain size variations of the sintered specimens with temperature. The apparent activation energies of the sintering and grain growth for Ti alloy particles are 85.91 ± 6.93 and 37.33 kJ/mol, respectively, similar to or slightly lower than those of pure Ti particles. The difference was attributed to the slower self-diffusion of Ti resulting from the alloying of Al and V into in the Ti matrix.
In recent years, researches on properties of nanocrystalline materials in comparison with coarse-grained materials have attracted a great deal of attention. The present investigation has been based on production of nanocrystalline Ti6Al4V powder from elemental powders by means of high energy mechanical milling. In this regard, Ti, Al and V powders were milled for up to 90 h and heat treated at different temperatures. The structural and morphological changes of powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and microhardness measurements. The results demonstrated that Ti(Al) and Ti(Al, V) solid solutions with grain size of 95 and 20 nm respectively form during mechanical alloying. In addition, an amorphous structure was obtained at longer milling times. The crystallization of amorphous phase upon annealing led to the formation of nanostructured Ti6Al4V phase with a grain size of 20-50 nm. The as-milled Ti6Al4V powder with amorphous structure exhibited a high microhardness of 720 Hv. Upon crystallization the hardness value reduced to 630 Hv which is higher than those reported for Ti6Al4V alloys processed by conventional routes.
Direct metal laser sintering or selective laser sintering is a rapid prototyping technique that consolidates, layer by layer, parts with complex shape from powders of a wide range of metallic materials. It has been used for fabrication of patient specific net-shaped parts of dense and porous titanium and its alloys for use as implants. But depending on the laser parameters, the powder can be fully melted during its consolidation. In this case, selective laser melting seems to be a more appropriate process denomination than selective laser sintering. In this work we use selective laser sintering/melting to consolidate Ti6Al4V porous parts from prealloyed powders in order to investigate the laser process parameters on the microstructure and mechanical properties of the parts. The consolidated samples were characterized by optical and scanning electron microscopy and compressive tests. The results showed a straight relationship between laser energy and mechanical properties.
Scientific Reports, 2023
The influence of heat treatment processes on microstructure, tensile and tribological properties of Ti6Al4V alloy was investigated. The specimens were heated for 30 min at 925 °C and then cooled at various rates by water quenching, air cooling, and furnace cooling. After that, the samples were aged for four hours at 600 °C. Three phases make up the microstructure: primary α-phase (α p), secondary α-phase (α s), and retained β-phase (β r). Cooling in the air and water followed by aging (AC + Aging and WQ + Aging) resulted, α s-phase precipitating inside β r-phase. The highest hardness of 35 HRC was recorded for WQ + Aging specimen due to existence of a high amount of β r-phase and precipitation of α s-phase. On the other hand, the lowest hardness of 26 HRC was obtained for the FC specimen. AC specimen achieved the highest elongation value of 14%. However, WQ + Aging specimen exhibited the highest ultimate tensile strength of 1028 MPa. For WQ + Aging and AC + Aging specimens, the ideal balance of strength and elongation was discovered. The wear resistance of solution-treated specimens was significantly improved by the aging process and 125% improvement could be achieved in WQ compared to WQ + Aging specimens.
Journal of Materials Engineering and Performance
This paper extends our previous work to investigate the effect of heat treatment on the microstructure of Ti-6Al-4V fabricated by selective laser melting. A post-heat treatment at 930 °C for 15 min followed by three cooling rates before and after hot isostatic pressing (HIP) treatment was applied. The findings illustrated that the microstructure of the quenched samples before the HIP treatment was characterized by a mixture of α + α′ phase with a microhardness value of 336 ± 6 HV0.3. Air cooling produced a structure dominated by the α phase, with ~ 7.5% of the β phase and a microhardness value of about 330 ± 4 HV0.3. Furnace cooling led to a mixture of α phase and ~ 17% of the β phase and hardness of 327 ± 6 HV0.3. After HIP followed by post-heat treatment, acicular α′ martensite with microhardness value 377 ± 2 HV0.3 dominated the quenched specimen microstructure. Following air cooling, the microstructure consisted of a mixture of α-lamella and β with some needles of the α with a m...
MATEC Web of Conferences
The most commonly used technology among the additive manufacturing is Direct Metal Laser Sintering (DMLS). This process is based on selective laser sintering (SLS). The method gained its popularity due to the possibility of producing metal parts of any geometry, which would be difficult or impossible to obtain by the use of conventional manufacturing techniques. Materials used in the elements manufacturing process are: titanium alloys (e.g. Ti6Al4V), aluminium alloy AlSi10Mg, etc. Elements printed from Ti6Al4V titanium alloy find their application in many industries. Details produced by additive technology are often used in medicine as skeletal, and dental implants. Another example of the DMLS elements use is the aerospace industry. In this area, the additive manufacturing technology produces, i.a. parts of turbines. In addition to the aerospace and medical industries, DMLS technology is also used in motorsport for exhaust pipes or the gearbox parts. The research objects are samples...
Modification of surface morphology of Ti6Al4V alloy manufactured by Laser Sintering
Open Engineering, 2016
The paper deals with the evaluation of relation between roughness parameters of Ti6Al4V alloy produced by DMLS and modified by abrasive blasting. There were two types of blasting abrasives that were used – white corundum and Zirblast at three levels of air pressure. The effect of pressure on the value of individual roughness parameters and an influence of blasting media on the parameters for samples blasted by white corundum and Zirblast were evaluated by ANOVA. Based on the measured values, the correlation matrix was set and the standard of correlation statistic importance between the monitored parameters was determined from it. The correlation coefficient was also set.