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71-535: The original Vereinigte Deutsche Metallwerke AG (VDM) was founded in 1930 by the takeover of Heddernheimer Kupferwerk and Süddeutsche Kabelwerk AG in Frankfurt by Berg-Heckmann-Selve AG in Altena. The merger took place on the initiative of Metallgesellschaft , which was the main shareholder of Heddernheimer Kupferwerke since 1893 and also took over the majority of the new corporate group. The global economic crisis had forced

142-559: A { 111 } {\displaystyle \left\{111\right\}} slip plane initially in the γ phase, where it is a perfect dislocation in that FCC structure. Since the γ' phase is primitive cubic instead of FCC due to the substitution of aluminum into the vertices of the unit cell, the perfect burgers vector along that direction in γ' is twice that of γ. For the a 2 [ 1 1 ¯ 0 ] {\displaystyle {\frac {a}{2}}\left[1{\bar {1}}0\right]} dislocation to enter

213-528: A manufacturing company is a stub . You can help Misplaced Pages by expanding it . This German corporation or company article is a stub . You can help Misplaced Pages by expanding it . Superalloy A superalloy , or high-performance alloy , is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength , thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance. The crystal structure

284-422: A barrier to further oxidation. Most commonly, aluminum and chromium are used in this role, because they form relatively thin and continuous oxide layers of alumina (Al 2 O 3 ) and chromia (Cr 2 O 3 ), respectively. They offer low oxygen diffusivities , effectively halting further oxidation beneath this layer. In the ideal case, oxidation proceeds through two stages. First, transient oxidation involves

355-498: A consistent strategy and investment. In 1969, the plant in Cologne was shut down and the remaining works were combined into seven business units: Despite the restructuring and some acquisitions in the 1970s, sales continued to decline. The company reacted with rationalization measures, a reorientation of the production strategy, the sale of individual company shares and the closure of unprofitable production units and plants. This reduced

426-454: A consolidation of previously competing companies. The new company had a share capital of 30 million Reichsmark and had branches and manufacturing facilities in Heddernheim , Gustavsburg , Mannheim , Nuremberg , Cologne and in Altena, Werdohl and Duisburg. The group's companies remained independent under their previous name (e. g. Heddernheimer Kupferwerk GmbH), but the production program

497-424: A ferritic (BCC) primary phase matrix, which is undesirable, as it is inferior to the high temperature strength exhibited by an austenitic (FCC) primary phase matrix. Gamma-prime (γ'): This phase is introduced as precipitates to strengthen the alloy. γ'-Ni3Al precipitates can be introduced with the proper balance of Al, Ni, Nb, and Ti additions. The two major types of austenitic stainless steels are characterized by

568-404: A higher melting point than nickel and has superior hot corrosion resistance and thermal fatigue. As a result, carbide-strengthened Co-based superalloys are used in lower stress, higher temperature applications such as stationary vanes in gas turbines. Co's γ/γ' microstructure was rediscovered and published in 2006 by Sato et al. That γ' phase was Co 3 (Al, W). Mo, Ti, Nb, V, and Ta partition to

639-415: A ladle (though with improved properties in a vacuum crucible). Conventional welding and casting is possible before heat-treatment. The original purpose was to produce high-performance, inexpensive bomb casings, but the material has proven widely applicable to structural applications, including armor. Single-crystal superalloys (SX or SC superalloys) are formed as a single crystal using a modified version of

710-410: A relatively large spacing between the dislocations compared to the particle diameter while a strongly coupled dislocation has a relatively comparable spacing compared to the particle diameter. This is determined not by the dislocation spacing, but by the size of the 𝛾’ particles. A weakly coupled dislocation occurs when the particle size is relatively small while a strongly coupled dislocation occurs when

781-892: A single-phase matrix of austenite iron (FCC) with an Al-oxide at the surface of the steel. Al is more thermodynamically stable in oxygen than Cr. More commonly, however, precipitate phases are introduced to increase strength and creep resistance. In Al-forming steels, NiAl precipitates are introduced to act as Al reservoirs to maintain the protective alumina layer. In addition, Nb and Cr additions help form and stabilize Al by increasing precipitate volume fractions of NiAl. At least 5 grades of alumina-forming austenitic (AFA) alloys, with different operating temperatures at oxidation in air + 10% water vapor have been realized: Operating temperatures with oxidation in air and no water vapor are expected to be higher. In addition, an AFA superalloy grade exhibits creep strength approaching that of nickel alloy UNS N06617. In pure Ni 3 Al phase Al atoms are placed at

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852-426: Is a concern. Oxidation involves chemical reactions of the alloying elements with oxygen to form new oxide phases, generally at the alloy surface. If unmitigated, oxidation can degrade the alloy over time in a variety of ways, including: Selective oxidation is the primary strategy used to limit these deleterious processes. The ratio of alloying elements promotes formation of a specific oxide phase that then acts as

923-945: Is achieved through the addition of C and a carbide former, such as Cr, Mo, W, Nb, Ta, Ti, or Hf, which drives precipitation of carbides at grain boundaries and thereby reduces grain boundary sliding. Adding elements is usually helpful because of solid solution strengthening, but can result in unwanted precipitation. Precipitates can be classified as geometrically close-packed (GCP), topologically close-packed (TCP) , or carbides. GCP phases usually benefit mechanical properties, but TCP phases are often deleterious. Because TCP phases are not truly close packed, they have few slip systems and are brittle. Also they "scavenge" elements from GCP phases. Many elements that are good for forming γ' or have great solid solution strengthening may precipitate TCPs. The proper balance promotes GCPs while avoiding TCPs. TCP phase formation areas are weak because they: The main GCP phase

994-481: Is by manipulating grain structure to reduce grain boundaries which tend to be pathways for easy diffusion. Typically this is done by manufacturing the superalloys as single crystals oriented parallel to the direction of the applied force. Superalloys were originally iron-based and cold wrought prior to the 1940s when investment casting of cobalt base alloys significantly raised operating temperatures. The 1950s development of vacuum melting allowed for fine control of

1065-424: Is debated whether the company was speculating after unwinding the long futures hedge since they became essentially exposed or naked against their forward customer commitments. It also became involved in a key European Court of Justice case (based on the tax treatment of dividends) that was heard at the same time as Hoechst . The company is now part of GEA Group Aktiengesellschaft. This article related to

1136-473: Is primarily since a high lattice misfit between the two phases results in a higher barrier to dislocation motion than a low lattice misfit. For Ni-based single-crystal superalloys, upwards of ten different kinds of alloying additions can be seen to improve creep-resistance and overall mechanical properties. Alloying elements include Cr, Co, Al, Mo, W, Ti, Ta, Re, and Ru. Elements such as Co, Re, and Ru have been described to improve creep resistance by facilitating

1207-661: Is provided by elements such as aluminium and chromium . Superalloys are often cast as a single crystal in order to eliminate grain boundaries , which decrease creep resistance (even though they may provide strength at low temperatures). The primary application for such alloys is in aerospace and marine turbine engines . Creep is typically the lifetime-limiting factor in gas turbine blades. Superalloys have made much of very-high-temperature engineering technology possible. Because these alloys are intended for high temperature applications their creep and oxidation resistance are of primary importance. Nickel (Ni)-based superalloys are

1278-416: Is strongly temperature-, stress-, orientation- and alloy-dependent. For a single-crystal superalloy, three modes of creep deformation occur under regimes of different temperature and stress: rafting, tertiary, and primary. At low temperature (~750 °C), SX alloys exhibits mostly primary creep behavior. Matan et al. concluded that the extent of primary creep deformation depends strongly on the angle between

1349-487: Is typically face-centered cubic (FCC) austenitic . Examples of such alloys are Hastelloy , Inconel , Waspaloy , Rene alloys , Incoloy , MP98T, TMS alloys, and CMSX single crystal alloys. Superalloy development relies on chemical and process innovations. Superalloys develop high temperature strength through solid solution strengthening and precipitation strengthening from secondary phase precipitates such as gamma prime and carbides . Oxidation or corrosion resistance

1420-634: Is γ'. Almost all superalloys are Ni-based because of this phase. γ' is an ordered L1 2 (pronounced L-one-two), which means it has a certain atom on the face of the unit cell, and a certain atom on the corners of the unit cell. Ni-based superalloys usually present Ni on the faces and Ti or Al on the corners. Another "good" GCP phase is γ''. It is also coherent with γ, but it dissolves at high temperatures. The United States became interested in gas turbine development around 1905. From 1910-1915, austenitic ( γ phase) stainless steels were developed to survive high temperatures in gas turbines. By 1929, 80Ni-20Cr alloy

1491-434: The a 6 ⟨ 211 ⟩ {\displaystyle {\frac {a}{6}}\left\langle 211\right\rangle } family ( Shockley partial dislocations ). The stacking faults between these partial dislocations can further provide another obstacle to the movement of other dislocations, further contributing to the strength of the material. There are also more slip systems that can be involved beyond

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1562-460: The { 111 } {\displaystyle \left\{111\right\}} slip plane and ⟨ 110 ⟩ {\displaystyle \left\langle 110\right\rangle } slip direction. At elevated temperature, the free energy associated with the anti-phase boundary (APB) is considerably reduced if it lies on a particular plane, which by coincidence is not a permitted slip plane. One set of partial dislocations bounding

1633-606: The dislocation -pinning behavior of grain boundaries, without introducing any amorphous solid into the structure. Single crystal (SX) superalloys have wide application in the high-pressure turbine section of aero- and industrial gas turbine engines due to the unique combination of properties and performance. Since introduction of single crystal casting technology, SX alloy development has focused on increased temperature capability, and major improvements in alloy performance are associated with rhenium (Re) and ruthenium (Ru). The creep deformation behavior of superalloy single crystal

1704-429: The 1940s. The early Nimonic series incorporated γ' Ni 3 (Al,Ti) precipitates in a γ matrix, as well as various metal-carbon carbides (e.g. Cr 23 C 6 ) at the grain boundaries for additional grain boundary strength. Turbine blade components were forged until vacuum induction casting technologies were introduced in the 1950s. This process significantly improved cleanliness, reduced defects, and increased

1775-498: The 60s and 70s, metallurgists changed focus from alloy chemistry to alloy processing. Directional solidification was developed to allow columnar or even single-crystal turbine blades. Oxide dispersion strengthening could obtain very fine grains and superplasticity . Co-based superalloys depend on carbide precipitation and solid solution strengthening for mechanical properties. While these strengthening mechanisms are inferior to gamma prime (γ') precipitation strengthening, cobalt has

1846-517: The APB cross-slips so that the APB lies on the low-energy plane, and, since this low-energy plane is not a permitted slip plane, the dissociated dislocation is effectively locked. By this mechanism, the yield strength of γ' phase Ni 3 Al increases with temperature up to about 1000 °C. Initial material selection for blade applications in gas turbine engines included alloys like the Nimonic series alloys in

1917-647: The German steelmaker Krupp took over one third, one year later 100 percent of the shares in the VDM Nickel Technologie AG . This division was formed from the merger of the Werdohl and Altena plants into the business area nickel in 1974. In the following years Krupp VDM - as the company was called - initially took over Precision Rolled Products (PRP) with production sites in New Jersey and Nevada and, on 1 October 2009,

1988-564: The ThyssenKrupp Group. Since 1 March 2014, VDM had once again been part of the ThyssenKrupp Group and has since been trading under the independent name of VDM Metals . In April 2015, ThyssenKrupp announced the sale of the VDM Group to the financial investor Lindsay Goldberg . On 1 August 2015, the sale was completed. In November 2019, the Spanish stainless steel producer Acerinox announced

2059-665: The United States to establish an operation. In 1887, the American Metal Company was incorporated as a joint stock company in New York with 51% Metallgesellschaft ownership so as to facilitate local decision-making; Metallgesellschaft executive Jacob Langeloth was named its president. In 1989 Michael Farmer, Baron Farmer formed the Metal & Commodity Company Ltd trading company, a subsidiary of Metallgesellschaft AG, which became

2130-596: The VDM for the war economy , almost all buildings and factories were heavily destroyed in the air raids on Frankfurt am Main during the Second World War . At the end of the war, the production collapsed completely, all works were shut down at the direction of the Allies and partly dismantled. It was not until 1946, under the leadership of Wilhelm Kirmser, that the gradual reconstruction and transition to civilian production began. In

2201-539: The activities of the sister company ThyssenKrupp Titanium. From then on, VDM became part of the ThyssenKrupp stainless steel division and operated under the name ThyssenKrupp VDM until 2012. Following the sale of the stainless steel division of ThyssenKrupp to Outokumpu in December 2012, VDM temporarily traded under the name Outokumpu VDM. At the end of November 2013 it was announced that VDM would be re-integrated into

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2272-405: The alloying additions used. Each addition serves a particular purpose in optimizing properties. Creep resistance is dependent, in part, on slowing the speed of dislocation motion within a crystal structure. In modern Ni-based superalloys, the γ'-Ni 3 (Al,Ti) phase acts as a barrier to dislocation. For this reason, this γ;' intermetallic phase, when present in high volume fractions, increases

2343-470: The conversion of various elements, especially the majority elements (e.g. nickel or cobalt). Transient oxidation proceeds until the selective oxidation of the sacrificial element forms a complete barrier layer. The protective effect of selective oxidation can be undermined. The continuity of the oxide layer can be compromised by mechanical disruption due to stress or may be disrupted as a result of oxidation kinetics (e.g. if oxygen diffuses too quickly). If

2414-404: The directional solidification technique, leaving no grain boundaries . The mechanical properties of most other alloys depend on the presence of grain boundaries, but at high temperatures, they participate in creep and require other mechanisms. In many such alloys, islands of an ordered intermetallic phase sit in a matrix of disordered phase, all with the same crystal lattice . This approximates

2485-400: The dislocations in the pair cross-slips into another plane, the dislocations become pinned since they can no longer move as a pair. This pinning reduces the ability for the dislocations to move in dislocation activated creep and improving the creep resistant properties of the material. Increasing the lattice misfit between 𝛾/𝛾' has also been shown to be beneficial for creep resistance. This

2556-445: The early 1950s, VDM became the world's largest manufacturer and distributor of raw, semi-finished and finished non-ferrous metals and alloys. The upswing reached its peak in the financial year 1960/61. Thereafter, the company continuously lost market share. Already for 1966/67 no dividend could be paid to shareholders. A major cause of the difficulties was the fragmented corporate structure of six separate companies, which did not allow

2627-526: The firm, which is now called Sempra Metals, and based in London). In 1993, the company lost 1.3 billion dollars suffering from flawed long hedge strategy in near term futures contracts that was meant to protect against forward sales commitments. A fall in spot prices forced margin calls for the company and the contracts were closed at a loss. Subsequently, the spot price increased and the company suffered even greater losses covering its customer commitments. It

2698-437: The first. In doing so, this significantly reduces the mobility of dislocations in the material which should inhibit dislocation activated creep. These dislocation pairs (also called superdislocations ) have been described as being either weakly or strongly coupled, the spacing between the dislocations compared to the size of the particle diameter being the determining factor between weak and strong. A weakly coupled dislocation has

2769-519: The formation of rafts of the γ' phase (as opposed to cuboidal precipitates). The presence of rafts can decrease creep rate in the power-law regime (controlled by dislocation climb), but can also potentially increase the creep rate if the dominant mechanism is particle shearing. Re tends to promote the formation of brittle TCP phases, which has led to the strategy of reducing Co, W, Mo, and particularly Cr. Later generations of Ni-based superalloys significantly reduced Cr content for this reason, however with

2840-408: The formation of stacking faults by reducing the stacking fault energy. Increasing number of stacking faults leading to the inhibition of dislocation motion. Other elements (Al, Ti, Ta) can favorably partition into and improve the nucleation of 𝛾’-phase. Diffusion is also a method of creep, and there are a few ways to limit diffusional creep. One primary way that superalloys can limit diffusional creep

2911-693: The layer is not continuous, its effectiveness as a diffusion barrier to oxygen is compromised. The stability of the oxide layer is strongly influenced by the presence of other minority elements. For example, the addition of boron , silicon , and yttrium to superalloys promotes oxide layer adhesion , reducing spalling and maintaining continuity. Oxidation is the most basic form of chemical degradation superalloys may experience. More complex corrosion processes are common when operating environments include salts and sulfur compounds, or under chemical conditions that change dramatically over time. These issues are also often addressed through comparable coatings. One of

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2982-410: The main strengths of superalloys are their superior creep resistant properties when compared to most conventional alloys. To start, 𝛾’-strengthened superalloys have the benefit of requiring dislocations to move in pairs due to the phase creating a high antiphase boundary (APB) energy during dislocation motion. This high APB energy makes it so that a second dislocation has to undo the APB energy created by

3053-567: The material contains no grain boundaries, carbides are unnecessary as grain boundary strengthers and were thus eliminated. Second and third generation superalloys introduce about 3 and 6 weight percent rhenium , for increased temperature capability. Re is a slow diffuser and typically partitions the γ matrix, decreasing the rate of diffusion (and thereby high temperature creep ) and improving high temperature performance and increasing service temperatures by 30 °C and 60 °C in second and third generation superalloys, respectively. Re promotes

3124-433: The material in the solution-annealed and hardened condition achieves higher hardness values and lower creep rates than, for example, Alloy C-263 (material number 2.4650, UNS N07263). The application temperature is up to 900 degrees Celsius. In June 2018, a nickel base alloy with 29 percent chromium and 2 percent aluminum was introduced, which is characterized in particular by its metal dusting resistance. The material has

3195-510: The material number 2.4842 or UNS N06699. Metallgesellschaft Metallgesellschaft AG was formerly one of Germany 's largest industrial conglomerates based in Frankfurt . It had over 20,000 employees and revenues in excess of 10 billion US dollars. It had over 250 subsidiaries specializing in mining, specialty chemicals (Chemetall), commodity trading , financial services , and engineering ( Lurgi ). Henry Merton & Company, Ltd

3266-498: The material of choice for these applications because of their unique γ' precipitates. The properties of these superalloys can be tailored to a certain extent through the addition of various other elements, common or exotic, including not only metals , but also metalloids and nonmetals ; chromium , iron , cobalt , molybdenum , tungsten , tantalum , aluminium , titanium , zirconium , niobium , rhenium , yttrium , vanadium , carbon , boron or hafnium are some examples of

3337-566: The number of employees from 14,200 (1970) to 6,700 in 1979. After a dramatic deterioration of the results in the financial year 1980/81, the parent plant in Frankfurt-Heddernheim was closed after 129 years on 31 March 1982. At this point in time, only the plants of the business area nickel (Altena, Unna and Werdohl) were still productive. In the following years, VDM gradually separated from all remaining production facilities and changed its name to MG Vermögensverwaltung AG in 1988. In 1988

3408-577: The oxide layer that forms on the steel surface: either chromia-forming or alumina-forming. Cr-forming stainless steel is the most common type. However, Cr-forming steels do not exhibit high creep resistance at high temperatures, especially in environments with water vapor. Exposure to water vapor at high temperatures can increase internal oxidation in Cr-forming alloys and rapid formation of volatile Cr (oxy)hydroxides, both of which can reduce durability and lifetime. Al-forming austenitic stainless steels feature

3479-536: The particle size is relatively large (such as when a superalloy has been aged for too long). Weakly coupled dislocations exhibit pinning and bowing of the dislocation line on the 𝛾’-particles. Strongly coupled dislocation behavior depends greatly on the dislocation line lengths and the resistances benefits they offer disappear once the particle size becomes large enough. Additionally, superalloys exhibit comparatively superior high temperature creep resistance due to thermally activated cross-slip of dislocations. When one of

3550-450: The pinned dislocation from another plane, allowing the pair of dislocations to push into the γ' phase. Furthermore, the burgers vector a 2 ⟨ 110 ⟩ {\displaystyle {\frac {a}{2}}\left\langle 110\right\rangle } family of dislocations are likely to decompose into partial dislocations in this alloy due to its low stacking fault energy , such as dislocations with burgers vector of

3621-417: The primary phase, with a fine dispersion between these known as secondary γ'. In order to improve the oxidation resistance of these alloys, Al, Cr, B, and Y are added. The Al and Cr form oxide layers that passivate the surface and protect the superalloy from further oxidation while B and Y are used to improve the adhesion of this oxide scale to the substrate. Cr, Fe, Co, Mo and Re all preferentially partition to

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3692-479: The promotion of TCP phases is not well-determined. Early reports claimed that Ru decreased the supersaturation of Re in the matrix and thereby diminished the susceptibility to TCP phase formation. Later studies noted an opposite effect. Chen, et al., found that in two alloys differing significantly only in Ru content (USTB-F3 and USTB-F6) that the addition of Ru increased both the partitioning ratio as well as supersaturation in

3763-520: The reduction in Cr comes a reduction in oxidation resistance . Advanced coating techniques offset the loss of oxidation resistance accompanying the decreased Cr contents. Examples of second generation superalloys include PWA1484, CMSX-4 and René N5. Third generation alloys include CMSX-10, and René N6. Fourth, fifth, and sixth generation superalloys incorporate ruthenium additions, making them more expensive than prior Re-containing alloys. The effect of Ru on

3834-498: The signing of a share-purchase-agreement to acquire VDM Metals. After approval through the competent antitrust authorities the deal was closed in March 2020. Alloy C-264 is a superalloy developed by VDM Metals and launched in 2018. In addition to the alloying element nickel, the alloy contains 25 percent chromium, 20 percent cobalt, about 5.5 percent molybdenum and 1.1 percent aluminum and 1.7 percent titanium. Various tests have shown that

3905-468: The strength and temperature capability. Modern superalloys were developed in the 1980s. First generation superalloys incorporated increased Al, Ti, Ta, and Nb content in order to increase the γ' volume fraction. Examples include: PWA1480, René N4 and SRR99. Additionally, the volume fraction of the γ' precipitates increased to about 50–70% with the advent of monocrystal solidification techniques that enable grain boundaries to be entirely eliminated. Because

3976-407: The strength of these alloys due to its ordered nature and high coherency with the γ matrix. The chemical additions of aluminum and titanium promote the creation of the γ' phase. The γ' phase size can be precisely controlled by careful precipitation strengthening heat treatments. Many superalloys are produced using a two-phase heat treatment that creates a dispersion of cuboidal γ' particles known as

4047-399: The tensile axis and the <001>/<011> symmetry boundary. At temperatures above 850 °C, tertiary creep dominates and promotes strain softening behavior. When temperature exceeds 1000 °C, the rafting effect is prevalent where cubic particles transform into flat shapes under tensile stress. The rafts form perpendicular to the tensile axis, since γ phase is transported out of

4118-511: The vertical channels and into the horizontal ones. Reed et al. studied unaxial creep deformation of <001> oriented CMSX-4 single crystal superalloy at 1105 °C and 100 MPa. They reported that rafting is beneficial to creep life since it delays evolution of creep strain. In addition, rafting occurs quickly and suppresses the accumulation of creep strain until a critical strain is reached. For superalloys operating at high temperatures and exposed to corrosive environments, oxidation behavior

4189-402: The vertices of the cubic cell and form sublattice A. Ni atoms are located at centers of the faces and form sublattice B. The phase is not strictly stoichiometric . An excess of vacancies in one of the sublattices may exist, which leads to deviations from stoichiometry. Sublattices A and B of the γ' phase can solute a considerable proportion of other elements. The alloying elements are dissolved in

4260-471: The world’s largest trader in physical copper and nickel, and he was its CEO from 1989-2000. In 1999 the company went public as it was floated on the London Stock Exchange under the title MG Plc with Farmer as its co-CEO; it was the first metals trader to be listed on the exchange. In 2000 he sold it to trading company Enron for $ 448 million, and Enron renamed it Enron Metals (in 2002, Enron sold

4331-399: The γ matrix of Cr and Re, and thereby promoted the formation of TCP phases. The current trend is to avoid very expensive and very heavy elements. An example is Eglin steel , a budget material with compromised temperature range and chemical resistance. It does not contain rhenium or ruthenium and its nickel content is limited. To reduce fabrication costs, it was chemically designed to melt in

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4402-498: The γ matrix while Al, Ti, Nb, Ta, and V preferentially partition to the γ' precipitates and solid solution strengthen the matrix and precipitates respectively. In addition to solid solution strengthening, if grain boundaries are present, certain elements are chosen for grain boundary strengthening. B and Zr tend to segregate to the grain boundaries which reduces the grain boundary energy and results in better grain boundary cohesion and ductility. Another form of grain boundary strengthening

4473-422: The γ phase. The γ' phase hardens the alloy through the yield strength anomaly . Dislocations dissociate in the γ' phase, leading to the formation of an anti-phase boundary . To give an example, consider a dislocation with a burgers vector of a 2 [ 1 1 ¯ 0 ] {\displaystyle {\frac {a}{2}}\left[1{\bar {1}}0\right]} traveling along

4544-460: The γ' phase unless there are two of them in close proximity along the same plane. However, the Peach-Koehler force between identical dislocations along the same plane is repulsive, which makes this a less favorable configuration. One possible mechanism involved one of the dislocations being pinned against the γ' phase while the other dislocation in the γ phase cross-slips into close proximity of

4615-421: The γ' phase, it will have to create a high energy anti-phase boundary , which will need another such dislocation along the plane to restore order (as the sum of the two dislocations would have the perfect a [ 1 1 ¯ 0 ] {\displaystyle a\left[1{\bar {1}}0\right]} burgers vector). It is thus rather energy prohibitive for the dislocation to enter

4686-443: The γ' phase, while Fe, Mn, and Cr partition to the matrix γ. The next family of Co-based superalloys was discovered in 2015 by Makineni et al. This family has a similar γ/γ' microstructure, but is W-free and has a γ' phase of Co 3 (Al,Mo,Nb). Since W is heavy, its elimination makes Co-based alloys increasingly viable in turbines for aircraft, where low density is especially valued. The most recently discovered family of superalloys

4757-690: Was a joint stock company, it was operated like a family business with key positions allocated to long-time loyal employees who were gradually rewarded with stock in the company. In 1889, on the recommendation of chemist Clemens Winkler , chemist Curt Netto accepted a post as head of the technical department. Metallgesellschaft was more diversified than its two main competitors who traded solely in copper, lead, and zinc while Metallgesellschaft also traded aluminum, nickel, and pyrite. The company became more involved internationally as Europe became more reliant on imported metals. In 1884, Metallgesellschaft sent Berthold Hochschild , brother of Zachary Hochschild , to

4828-572: Was computationally predicted by Nyshadham et al. in 2017, and demonstrated by Reyes Tirado et al. in 2018. This γ' phase is W free and has the composition Co 3 (Nb,V) and Co 3 (Ta,V). Steel superalloys are of interest because some present creep and oxidation resistance similar to Ni-based superalloys, at far less cost. Gamma (γ): Fe-based alloys feature a matrix phase of austenite iron (FCC). Alloying elements include: Al, B, C, Co, Cr, Mo, Ni, Nb, Si, Ti, W, and Y. Al (oxidation benefits) must be kept at low weight fractions (wt.%) because Al stabilizes

4899-684: Was previously a branch of the Metallgesellschaft. Metallgesellschaft AG was incorporated in Frankfurt am Main in 1881 by Wilhelm Ralph Merton , his father Ralph Merton, and Leo Ellinger. Merton was responsible for business strategy, Ellinger for operations, and a cousin of Merton, Zachary Hochschild , for marketing and international activities. Their main competition were the two other large metal trading companies of Germany: Aron Hirsch & Sohn in Halberstadt , and Beer, Sondheimer & Co in Frankfurt am Main . Although Metallgesellschaft

4970-507: Was redistributed by material group to the individual plants. In March 1934, VDM moved its headquarters to Frankfurt am Main . The incipient rearmament of the Wehrmacht skyrocketed the demand for light metal products. By 1939, the number of employees at VDM rose to 21,000, mainly due to the production of variable pitch propellers for aircraft of the Luftwaffe . Because of the great importance of

5041-788: Was the norm, with small additions of Ti and Al. Although early metallurgists did not know it yet, they were forming small γ' precipitates in Ni-based superalloys. These alloys quickly surpassed Fe- and Co-based superalloys, which were strengthened by carbides and solid solution strengthening. Although Cr was great for protecting the alloys from oxidation and corrosion up to 700 °C, metallurgists began decreasing Cr in favor of Al, which had oxidation resistance at much higher temperatures. The lack of Cr caused issues with hot corrosion, so coatings needed to be developed. Around 1950, vacuum melting became commercialized, which allowed metallurgists to create higher purity alloys with more precise composition. In

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