Browse Topic: Powder metallurgy
Blended metal powders offer a compelling alternative to pre-alloyed powders in metal additive manufacturing by providing access to a wider range of alloy compositions and avoiding the high costs in producing pre-alloyed powders. In this work, a new and crack-free Ti-5AlMnScZrMgSiFe alloy (in wt.%) was manufactured by laser powder bed fusion (L-PBF) from mixed powders to investigate the microstructures, mechanical performance of printed parts. Ti-5 AlMnScZrMgSiFe alloy contains both alpha (α) and alpha prime (α′) phases. Further microstructural characterizations show that the L-PBF Ti-5 AlMnScZrMgSiFe contain dense dislocations and twins formed in additive manufacturing process. The as-printed Ti-5 AlMnScZrMgSiFe alloy exhibits a tensile fracture strength of ~950 MPa with a fracture elongation of ~12.5%. The eye-catching properties are attributed to the dense dislocations, nano-twins and solid-solution strengthening.
For brake and clutch components of aircraft vehicles which require higher mechanical strength and wear resilient, light-weight aluminium composites were developed infusing solid lubricant. In this study, hybrid composites were developed using powder metallurgy route with aluminum alloy AA356 and various amounts of zirconium oxide (ZrO2) (0, 5, 10, 15, and 20 wt.%) as reinforcements. A solid lubricant hexagonal boron nitride (hBN) at a fixed 5 wt.% is considered. Following the appropriate ASTM guidelines, the specimens were mechanically characterized by measuring their density, porosity, micro-hardness, compression strength, impact strength, and flexural strength, among other properties. The findings showed that the composites' mechanical and physical behaviour were greatly affected by the inclusion of ZrO2. Porosity increased as a result of particle clustering and interfacial voids, while density increased gradually as ceramic content increased. Consistently increasing ZrO2 addition led to micro-hardness improvements; at 20 wt.% reinforcement, values reached their maximum, indicating that the hard ceramic phase contributed to better surface resistance. The best balance between particle reinforcement and matrix continuity was suggested by the compression and flexural strengths peaking at 15 wt.% ZrO2. However, when the addition was raised to 20 wt.%, brittleness and porosity began to marginally deteriorate. Unreinforced and lower ZrO2 composites had superior toughness in impact, whereas materials with a higher content had a poorer energy absorption capacity. The 5 wt.% hBN improved fracture arresting capabilities and helped load transmission over the interface. Inclusion of hBN provides solid-lubricating tribofilm formation that enhances the tribological performance. This study reveals that AA356/ZrO2-hBN hybrid composites have good hardness and compressive strength improvements, with 15 wt.% ZrO2 being the best composition with good strength, toughness, and wear resistance.
To evaluate the performance evolution patterns of road structures under natural environmental conditions and loading, data were collected from the RIOHTrack system. Pavement deflection, smoothness, and skid resistance were selected as evaluation indicators. The performance evolution characteristics over 50 million load cycles were analyzed to investigate the impact of different structural configurations on service performance. The study results are summarized as follows: The deflection basin area exhibits significant annual cyclic fluctuations, indicating that ambient temperature significantly affects pavement deflection. The initial rapid decrease in texture depth was attributed to the compaction of the surface layer under traffic loading, leading to a reduction in texture depth. Differences in tire and subgrade stiffness can cause variations in texture depth across various scenarios. Circular pavement structures' smoothness can be categorized into three classes; however, even within the same class, different combinations of roadway structures can result in substantial variations in pavement IRI values. These research findings are crucial for understanding the evolution laws of road performance and developing long-life pavements.
Researchers have demonstrated a new technique that uses lasers to create ceramics that can withstand ultra-high temperatures, with applications ranging from nuclear power technologies to spacecraft and jet exhaust systems. North Carolina State University, Raleigh, NC A new technique that leverages the concept of sintering, can be used to create ceramic coatings, tiles or complex three-dimensional structures, which allows for increased versatility when engineering new devices and technologies. “Sintering is the process by which raw materials - either powders or liquids - are converted into a ceramic material,” says Cheryl Xu, co-corresponding author of a paper on this research and a Professor of Mechanical and Aerospace Engineering at North Carolina State University (NCSU). “For this work, we focused on an ultrahigh temperature ceramic called hafnium carbide (HfC). Traditionally, sintering HfC requires placing the raw materials in a furnace that can reach temperatures of at least 2,200 degrees Celsius - a process that is time-consuming and energy intensive.
A new technique that leverages the concept of sintering, can be used to create ceramic coatings, tiles or complex three-dimensional structures, which allows for increased versatility when engineering new devices and technologies.
Gamma Alloys manufactures aluminum matrix composite bearing liners for helicopter transmissions that have the performance of steel liners at one third the weight. These bearing liners have diameters between 2.5 and 24 inches. Our composites are made by blending aluminum powders with spheroidized alumina particles. These powders are then vacuum hot pressed into billets. These billets are then extruded into shapes that can be machined into bearing liners. The extrusion process transforms the powder metallurgy product into a wrought product. Over 2000 liners have been made and are currently flying in R&D vehicles since 2018 with no maintenance issues.
The initial powder used for the manufacturing of NdFeB permanent magnets is usually prepared through rapid cooling, either by melt spinning or strip casting. The powders produced by these two methods are suitable for different applications: while melt-spun powder is a good initial material for bonded and hot-deformed magnets, strip-cast powder is normally used for sintered magnets. To investigate the suitability of using strip-cast powder to manufacture hot-deformed magnets, NdFeB powder prepared by strip casting was hot pressed (without particle alignment) and compared with melt-spun powder prepared under the same conditions (700 °C, 45 MPa, 90 min). Although the processing parameters are the same (pressed in the same mold), the magnetic properties of the magnets made from the two powders are significantly different. Surprisingly, the magnet made from the strip-cast powder (after ball milling) shows comparable magnetic properties to those of isotropic magnets, with coercivity (HcJ) of 1270 kA/m and remanence (Br) of 0.7 T, while that made from the melt-spun powder exhibits much lower properties: HcJ = 480 kA/m, Br = 0.5 T, although the melt-spun powder initially shows much better magnetic properties than the strip-cast powder. Possible reasons for such a difference in magnetic properties are discussed. It was shown that the particle size of the initial powder plays an important role in determining the final magnetic properties of the hot-pressed magnets.
A novel sintering method of bridging the two mechanically polished and oriented single-crystals together face-to-face in a non- environmental controlled atmosphere to fabricate the bicrystal substrate of NaCl of macroscopic thickness, with a common zone axis and having planarity over large areas, has been developed. Epitaxial [001] bicrystalline thin face-centered cubic (fcc) metal film of surface-reactive metal-containing tilt grain boundary across the interface is first grown in high vacuum directly by flash deposition on initially fabricated [001] oriented bicrystalline substrate of NaCl. The [001] tilt boundary, thus produced, and is examined by electron microscopy to characterize grain boundary morphology and structure. The findings of some preliminary investigations are then presented. A distinct atomic structure is observed for 310 and 210 inclination. Both HAADF-STEM and Diffraction images reveal that such fabricated high-angle grain boundary accommodates minor deviations from the exact high coincidence density ∑=5 misorientation. The potential use of the present technique is extended to produce a wide variety of homophase bicrystals, containing grain boundaries at the midplane, normal to any crystallographic surface without the necessity of a separate bonding operation.
Recent advances in both alloy development and additive manufacturing have enabled the production of ultrahigh-strength steels in nearnet shape parts. Army Research Laboratory, Aberdeen Proving Ground, Maryland Ultrahigh-strength steels are traditionally defined as those steels with a minimum yield strength of approximately 1380 MPa. Notable examples of steels in this category include AISI 4130, AISI 4140, and AISI 4340. In many cases, maximizing the performance of these alloys requires a rather complex approach that involves a series of tempering, annealing, or stress-relieving treatments. As a result, they are produced using a variety of traditional processing methods such as casting, rolling, extrusion, or forging. These traditional methods - combined with the ultrahigh strength of the steels - often meant that the production of complex, near-net shape parts of high quality was quite difficult. In addition, these production methods often entailed repetitive treatments or long production cycles, both of which resulted in elevated production costs. Additive manufacturing (AM, also known as 3D printing) has recently been recognized as a manufacturing method that enables the production of near-net shape parts. In these methods, a complex part is iteratively built in a layer-by-layer process that involves powder deposition followed by selective melting/sintering of the powder to form the part. With the continued development of processing lasers, it is now possible to form fully dense components from a wide range of metals powders, including refractory alloys, steels, and other high-temperature alloys.
General Motors (GM) is working towards a future world of zero crashes, zero emissions and zero congestion. It’s “Ultium” platform has revolutionized electric vehicle drive units to provide versatile yet thrilling driving experience to the customers. Three variants of traction power inverter modules (TPIMs) including a dual channel inverter configuration are designed in collaboration with LG Magna e-Powertrain (LGM). These TPIMs are integrated with other power electronics components inside Integrated power electronics (IPE) to eliminate redundant high voltage connections and increase power density. The developed power module from LGM has used state-of-the art sintering technology and double-sided cooled structure to achieve industry leading performance and reliability. All the components are engineered with high level of integration skills to utilize across TPIM variants. Each component in the design is rigorously analyzed and tested from component to system levels to ensure high reliability, power density and efficiency. All these topics mentioned above are within the scope of this paper.
Powder metallurgy of 3065IS temperature and strain rate were only two of the variables used to investigate the higher permeability of an iron alloy. A strain rate vs. stress plot revealed a critical value. This demonstrated that the functioning of the alloy was comparable to that of other materials in its class. We used a transmission electron microscope to examine the microstructure of routinely twisted materials to determine particle characteristics and precipitate distribution. This allowed us to gain a better understanding of the internal workings of materials. Using constitutive equations, we investigated the link between temperature and stress. This study's findings were incorporated into equations describing the material's high thermal behaviour, and a modified version of the cosec equation was used to analyse this reliance. Effective stress was defined as the distinction between actual stress and a present limit. It has been shown that the presence of ferrous particles and deposited inter - metallic phase may result in a continuous threshold stress that changes with temperature. The temperature of a material influences the stress applied to it.
Sintered parts mechanical properties are very sensitive to final density, which inevitable cause an enormous density gradient in the green part coming from the compaction process strategy. The current experimental method to assess green density occurs mainly in set up by cutting the green parts in pieces and measuring its average density in a balance using Archimedes principle. Simulation is the more accurate method to verify gradient density and the main benefit would be the correlation with the critical region in terms of stresses obtained by FEA and try to pursue the optimization process. This paper shows a case study of a part that had your fatigue limit improved 1000% using compaction process simulation for better optimization.
A Penn State-led team of researchers have created a new process to fabricate large perovskite devices that is more cost- and time-effective than previously possible — and may accelerate future materials discovery.
This specification covers a polyimide plastic in the form of isostatically molded rod, bar, and tube, unidirectionally molded plaque, and direct formed parts.
This specification covers a titanium alloy in the form of prealloyed powder.
The relative adhesive wear performance of rolling element bearing material pairs was evaluated using a constant entrainment stepped slide-to-roll (SRR) test protocol. Raceway materials included M50, M50NiL, 440C, and powder metallurgy M62 (M62 PM). Rolling element materials included M50, 440C, and Si3N4. The material interfaces of both all-steel and hybrid configurations were ranked based on the survived SRR. The Si3N4 and steel hybrid pairing increased the adhesive wear resistance, reduced the tractive effort of the contact, and enabled operation with reduced component temperatures throughout each test. Post-test wear track morphology and chemistry were investigated using light microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Steel alloying elements and elevated levels of oxygen were identified within the Si3N4 wear track from each hybrid material pair.
This specification prescribes process requirements for batch processing of used, metal powder originating from an existing additive manufacturing process workflow for reuse in subsequent additive manufacturing of aerospace parts in non-closed loop additive manufacturing machines. Such powders may be pre-alloyed or commercially pure. This specification is not limited to a specific additive manufacturing process workflow as the originating source of material to be reused. It is intended to define those procedures and requirements necessary to achieve required cleanliness and performance of metal powder feedstock to be reintroduced into the same additive manufacturing process from which such powder originated. This specification is intended to be used in conjunction with relevant AMS powder specifications and AMS process specifications for additive manufacturing. Unless otherwise specified, powder prepared for reuse following this specification is intended to be conforming in physical and chemical attributes as defined by the originating virgin powder specification for the purposes of producing aerospace parts, providing equivalent characteristics and properties as specified by the corresponding AMS material specification.
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