scholarly journals Analysis of microstructural facet fatigue failure in ultra-fine grained powder metallurgy Ti-6Al-4V produced through hydrogen sintering

2020 ◽  
Vol 131 ◽  
pp. 105355 ◽  
Author(s):  
Matthew K. Dunstan ◽  
James D. Paramore ◽  
Z. Zak Fang ◽  
Jonathan P. Ligda ◽  
Brady G. Butler
Keyword(s):  
Powder Metallurgy ◽  
Fatigue Failure ◽  
Fine Grained

Ultra-Fine Grained Ti-15Mo Alloy Prepared by Powder Metallurgy

2018 ◽  
Vol 941 ◽  
pp. 1276-1281
Author(s):  
Anna Terynková ◽  
Jiří Kozlík ◽  
Kristína Bartha ◽  
Tomáš Chráska ◽  
Josef Stráský
Keyword(s):  
Powder Metallurgy ◽  
Bulk Material ◽  
Alpha Phase ◽  
Full Density ◽  
Fine Grained ◽  
Cryogenic Milling ◽  
Aircraft Manufacturing ◽  
Plasma Sintering ◽  
Beta Matrix ◽  
Spark Plasma

Ti-15Mo alloy belongs to metastable β-Ti alloys that are currently used in aircraft manufacturing and Ti15Mo alloy is a perspective candidate for the use in medicine thanks to its biotolerant composition. In this study, Ti15Mo alloy was prepared by advanced techniques of powder metallurgy. The powder of gas atomized Ti-15Mo alloy was subjected to cryogenic milling to achieve ultra-fine grained microstructure within the powder particles. Powder was subsequently compacted using spark plasma sintering (SPS). The effect of cryogenic milling on the microstructure and phase composition of final bulk material after SPS was studied by scanning electron microscopy. Sintering at 750°C was not sufficient for achieving full density in gas atomized powder, while milled material could be successfully sintered at this temperature. Alpha phase particles precipitated during sintering and their size, as well as the size of beta matrix grains, was strongly affected by the sintering temperature.

scholarly journals Processing of Elemental Titanium by Powder Metallurgy Techniques

2013 ◽  
Vol 765 ◽  
pp. 383-387 ◽  
Author(s):  
Leandro Bolzoni ◽  
E.M. Ruiz-Navas ◽  
Elena Gordo
Keyword(s):  
Powder Metallurgy ◽  
Automotive Industry ◽  
Aerospace Industry ◽  
High Strength ◽  
Production Costs ◽  
Fine Grained ◽  
Good Corrosion Resistance ◽  
Fabrication Cost ◽  
Near Net Shape ◽  
Industrial Level

Titanium is characterised by an outstanding combination of properties like high strength, low density, good corrosion resistance and biocompatibility. Nonetheless, widespread employment of titanium at the industrial level, especially in the automotive industry, has not been achieved yet because of its high extraction and production costs. Consequently, titanium finds applications mainly in high demanding sectors, such as the aerospace industry or to produce biomedical devices, where the final high cost is not the principal issue. The processing of titanium and its alloys by means of powder metallurgy (PM) techniques is claimed to be a suitable way to reduce the fabrication cost of titanium products as well as offering the possibility to design new alloys which are difficult to obtain using the conventional metallurgical route, for example due to segregation of heavy alloying elements. This work deals with the processing of hydride-dehydride elemental titanium powder by means of different PM methods and aims at investigating the processing of near net-shape, chemically-homogeneous and fine-grained titanium-based components. In particular, properties achievable (i.e. relative density, microstructure and mechanical properties) and problems related to the processing of elemental titanium, by both the conventional PM route of pressing and sintering and the advanced PM method of hot-pressing, are presented.

scholarly journals Properties Comparison of Ti-Al-Si Alloys Produced by Various Metallurgy Methods

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3084 ◽  
Author(s):  
Anna Knaislová ◽  
Pavel Novák ◽  
Jaromír Kopeček ◽  
Filip Průša
Keyword(s):  
Fracture Toughness ◽  
Phase Composition ◽  
Powder Metallurgy ◽  
Titanium Aluminide ◽  
Titanium Aluminides ◽  
Compression Tests ◽  
Large Area ◽  
Fine Grained ◽  
Central Porosity ◽  
Fine Grained Structure

Melting metallurgy is still the most frequently used and simplest method for the processing of metallic materials. Some of the materials (especially intermetallics) are very difficult to prepare by this method due to the high melting points, poor fluidity, or formation of cracks and pores after casting. This article describes the processing of Ti-Al-Si alloys by arc melting, and shows the microstructure, phase composition, hardness, fracture toughness, and compression tests of these alloys. These results are compared with the same alloys prepared by powder metallurgy by the means of a combination of mechanical alloying and spark plasma sintering. Ti-Al-Si alloys processed by melting metallurgy are characterized by a very coarse structure with central porosity. The phase composition is formed by titanium aluminides and titanium silicides, which are full of cracks. Ti-Al-Si alloys processed by the powder metallurgy route have a relatively homogeneous fine-grained structure with higher hardness. However, these alloys are very brittle. On the other hand, the fracture toughness of arc-melted samples is immeasurable using Palmqvist’s method because the crack is stopped by a large area of titanium aluminide matrix.

Inquiry into Extending the Life of Valve Rocker Arms in High Performance and Large Capacity Engine

2017 ◽  
Author(s):  
Kadra Branker
Keyword(s):  
Powder Metallurgy ◽  
Residual Stresses ◽  
Fatigue Failure ◽  
Material Properties ◽  
High Performance ◽  
Testing Methods ◽  
Large Capacity ◽  
Inquiry Based Learning ◽  
Air Intake ◽  
Manufacturing Methods

Valve rocker arms in an engine aid in the timing of the valves. The valves control the air intake and gas exhaust from the cylinder chamber in the engine which affect the efficiency of the engine. Although the rockers are small and fairly inexpensive compared to other parts in the engine the disruption in the timing of the valves can have catastrophic consequences once they fail. Rockers experience considerable cyclic forces due to the repeated tapping on the valves, increasing with the revolutions of the engine. As a result rocker arms exhibit fatigue failure which is amplified by residual stresses that are induced during manufacture. The manufacturing methods employed in making the rockers influence material properties along with the chosen materials which require specific methods of preparation. Proposed solutions include better alloying using powder metallurgy and the use of other materials in the design, such as ceramics, to improve their resilience and strength. The types of testing methods to determine the best solution and other possible areas of consideration, when solving the problem, will also be acknowledged. This presentation will illustrate how inquiry based learning can be used to solve the problem. It will address why valve rocker arms fail while assessing past and present research geared towards finding a solution, with emphasis on the manufacturing methods and material properties

scholarly journals Fatigue Behaviour and Crack Initiation in CoCrFeNiMn High-Entropy Alloy Processed by Powder Metallurgy

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1110 ◽  
Author(s):  
Zdeněk Chlup ◽  
Stanislava Fintová ◽  
Hynek Hadraba ◽  
Ivo Kuběna ◽  
Monika Vilémová ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Cyclic Loading ◽  
Crack Nucleation ◽  
Milled Powder ◽  
Fatigue Behaviour ◽  
Initiation Site ◽  
High Entropy Alloy ◽  
High Entropy ◽  
Fine Grained ◽  
Small Change

Single-phase equiatomic five-element high entropy alloy CoCrFeMnNi was prepared by powder metallurgy. Two materials with ultra-fine-grained microstructure were prepared by spark plasma sintering (SPS) of ball-milled powder at two sintering times (5 and 10 min), assigned as HEA 5 and HEA 10, respectively. Basic microstructural and mechanical properties were evaluated. The median grain size of the microstructures was determined to be 0.4 and 0.6 μm for HEA 5 and HEA 10, respectively. The differences in the microstructure led to a significant change in strength and deformation characteristics evaluated at room temperature. The effect of cyclic loading was monitored by three-point bending fatigue test. The results show that even relatively small change in the microstructure causes a significant effect on fatigue life. The fatigue endurance limit was measured to be 1100 MPa and 1000 MPa for HEA 5 and HEA 10, respectively. The detailed fractographic analysis revealed that abnormally large grains, localised in the microstructure on the tensile loaded surface, were a typical fatigue initiation site. The formation of (nano) twins together with dislocation slips caused the crack nucleation because of the cyclic loading.

scholarly journals Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1215
Author(s):  
Igor Razumovskii ◽  
Alla Logacheva ◽  
Vsevolod Razumovskiy ◽  
Ivan Logachev ◽  
Mikhail Razumovsky
Keyword(s):  
Powder Metallurgy ◽  
Grain Boundaries ◽  
Hot Isostatic Pressing ◽  
Cohesion Energy ◽  
Alloy Matrix ◽  
Modern Approach ◽  
Fine Grained ◽  
Heat Resistant ◽  
Polycrystalline Alloys ◽  
Molar Energy

The modern approach to the design of heat-resistant metal alloys (HRAs) is analyzed, according to which the creep rupture characteristics of an alloy are mostly determined by the strength of interatomic bonding at grain boundaries (GBs) and in the bulk of a matrix phase. The main attention is paid to the concept of “low alloying additions” to polycrystalline alloys with transition metals, because of which the cohesive strength of the GBs and the cohesion energy of the alloy matrix are increased. This approach is especially important in relation to alloys obtained by powder metallurgy, which, in the compacted state, are fine-grained polycrystals. The methodology for calculating the key parameters of the theory (the energy of impurity segregation to the grain boundaries Egb and to the free surface Efs, as well as the values of the partial molar energy of the cohesion of the alloys) from the first principles is given. The results of applying the theory to the study of Ni-, Cr- and Ti-based alloys and the development of new HRAs based on them are presented. Typical defects in the microstructures of objects obtained using additive technologies (AT) and the application efficiency of standard methods of processing powder alloys (Hot Isostatic Pressing (HIP), heat treatment (HT)) to improve the microstructure and increase the mechanical properties are considered.

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