Aircraft Metals Technology Journeyman

Nickel based alloys must be held at a temperature range of 900 to 1600 degrees F in order to age-harden them.

The correct answer is .465 by .75. This is because when .465 is divided by .75, the quotient is .62.

The Pythagorean theorem states that in a right triangle, the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides. This means that if we have a right triangle with side lengths a, b, and c (where c is the hypotenuse), then c^2 = a^2 + b^2. Therefore, the correct answer is "sum of the squares of the other two sides."

A solid solution is formed when the elements of a metal are absorbed into each other, resulting in a homogeneous mixture where the individual components cannot be distinguished. In a solid solution, the atoms of the different elements are evenly distributed throughout the material, creating a single phase. This is different from a mechanical mixture, where the components can be seen and are not uniformly distributed. A chemical compound refers to a substance formed by the chemical combination of different elements, while a pure metal refers to a material composed solely of one type of metal.

Nickel-cobalt super alloys are known for their exceptional corrosion resistance at elevated temperatures. This means that these alloys can withstand the effects of oxidation and other chemical reactions that can occur at high temperatures, making them highly suitable for use in environments with extreme heat. This property is advantageous as it ensures the longevity and reliability of the alloys in such conditions, making them ideal for applications in industries such as aerospace, power generation, and chemical processing.

To divide fractions, we multiply the first fraction by the reciprocal of the second fraction. In this case, we have (5/6) ÷ (3/5). The reciprocal of 3/5 is 5/3. Multiplying the fractions, we get (5/6) × (5/3) = 25/18. This fraction can be simplified to the mixed number 1 7/18. Therefore, the result of dividing 5/6 by 3/5 is 1 7/18.

During the heat treating of low alloy steel, the transformation occurs at slightly lower temperatures than when heating. This is because during the slow cooling process, the steel undergoes a phase change from austenite to ferrite and/or pearlite. This transformation occurs at a lower temperature compared to when the steel is being heated, where the austenite phase is formed.

Circulating air furnaces are designed specifically for operations that require low temperatures. These furnaces are capable of circulating cool air throughout the system, allowing for efficient cooling and maintaining a controlled low temperature environment. They are not suitable for operations that require high temperatures, carburizing atmospheres, or reactive atmospheres.

The T6 designator for aluminum alloys indicates that the material has undergone solution heat treatment and artificially aging. Solution heat treatment involves heating the alloy to a high temperature and then rapidly cooling it to improve its mechanical properties. Artificial aging is a process that follows solution heat treatment and involves heating the alloy at a lower temperature to further enhance its strength and hardness. Therefore, the correct answer is "and artificially aged."

During the heat treating of low alloy steel, transformation occurs at temperatures far below the heating temperatures. This means that the transformation takes place at a lower temperature than the temperature at which the steel was heated. This is a common phenomenon in heat treating processes, where the steel is heated to a high temperature to achieve certain desired properties, and then cooled rapidly to induce the transformation at a lower temperature.

To prevent excessive grain growth when heat treating carbon and alloy steel, it is necessary to soak the material only long enough to ensure uniform heating. This means that the material should be heated for the minimum amount of time required to reach a uniform temperature throughout. If the soaking time is too short, the material may not be heated evenly, leading to uneven grain growth. On the other hand, if the soaking time is too long, there is a risk of excessive grain growth, which can negatively impact the mechanical properties of the steel. Therefore, the correct approach is to soak the material only for the required duration to achieve uniform heating.

Age hardening is a process used to increase the strength and hardness of a material, typically a metal alloy, by precipitation hardening. During age hardening, the material is heated to a temperature below its recrystallization temperature, followed by a controlled cooling process. This allows for the formation of fine precipitates within the material, which act as barriers to dislocation movement, resulting in increased strength. The formation of these precipitates also leads to a refinement of the grain structure, making the grains smaller and more uniform in size. Therefore, the correct answer is that age hardening refines the grains.

Eutectic melting in aluminum alloys refers to the process in which the alloy reaches its eutectic composition and melts at a specific temperature. During this process, the alloy undergoes a phase change and forms a eutectic microstructure, which consists of intermetallic compounds and a eutectic mixture. This eutectic microstructure can lead to a loss of corrosion resistance in the alloy. The intermetallic compounds and the eutectic mixture can create galvanic cells, which accelerate the corrosion process. Therefore, eutectic melting in aluminum alloys results in a loss of corrosion resistance.

The highest normalizing temperature is found in hypereutectoid steel. Hypereutectoid steel contains a higher percentage of carbon than the eutectoid and hypoeutectoid steels. Normalizing is a heat treatment process that involves heating the steel above its critical temperature and then cooling it in still air. This process helps to refine the grain structure and improve the mechanical properties of the steel. Since hypereutectoid steel has a higher carbon content, it requires a higher temperature to achieve the desired grain refinement and transformation.

The statement "best whenever etching is needed" is not a correct statement about using citric acid for passivation. Passivation is a process that helps to prevent corrosion on metal surfaces, and citric acid is commonly used as a passivating agent. However, citric acid is not specifically used for etching purposes. Etching involves selectively removing material from a surface, whereas passivation aims to create a protective layer on the surface. Therefore, this statement is incorrect.

Aluminum shot is not a material used for peening operations. Peening is a process in which small metallic particles are propelled at high velocity onto a surface to create compressive stresses and improve the surface properties. Cast steel shot, ceramic bead shot, and stainless steel cut wire shot are commonly used materials for peening operations due to their hardness and durability. However, aluminum shot is not typically used for peening as it is a softer material and may not provide the desired peening effect.

To control decarburizing with martensitic stainless steels when heat treating, using a carburizing atmosphere is the correct answer. Carburizing is a process in which carbon is diffused into the surface of the steel, forming a carbon-rich layer. This helps to counteract the decarburization that can occur during heat treatment, where the carbon content of the steel is reduced, leading to a loss of hardness and other desirable properties. By introducing a carburizing atmosphere, the steel is protected from decarburization, ensuring that it retains its desired properties.

Solution treating aluminum alloys involves heating the alloy to a specific temperature and then rapidly cooling it. This process helps in improving the corrosion resistance of the alloy. By subjecting the alloy to solution treatment, the microstructure of the alloy is modified, reducing the susceptibility to corrosion. This is achieved by dissolving and redistributing the alloying elements, resulting in a more uniform and corrosion-resistant structure. Therefore, solution treating aluminum alloys not only enhances their strength but also improves their corrosion resistance.

Natural aging and artificial precipitation hardening are two different processes used to strengthen aluminum alloys. Natural aging occurs when the alloy is left at room temperature for an extended period, allowing the natural precipitation of strengthening phases. On the other hand, artificial aging involves heating the alloy at a higher temperature to speed up the precipitation process. However, in terms of strength, there is no noticeable difference between natural aging and artificial precipitation hardening.

The size of the passivation selection is not a variable that needs to be considered and controlled. When selecting passivation, factors such as time, temperature, and concentration are important to ensure the desired outcome. However, the size of the passivation selection does not have a significant impact on the process and therefore does not need to be taken into account.

The variable that is being referred to when classifying heat treating furnaces is the air condition. This means that the classification of these furnaces depends on the specific air conditions that are used in the process of heat treatment. The air condition plays a crucial role in determining the temperature and atmosphere within the furnace, which in turn affects the quality and properties of the heat-treated material.

Spheroidizing is the process that produces the most malleable condition in high carbon steel. During spheroidizing, the steel is heated to a temperature below the eutectoid point and then slowly cooled. This process causes the formation of spherical carbides, which helps to improve the steel's ductility and malleability. Spheroidizing also reduces the hardness of the steel, making it easier to shape and work with. Carburizing, hardening, and annealing are other heat treatment processes that have different effects on the properties of high carbon steel.

The correct answer is "is a mechanical mixture". This means that at room temperature, the cementite grain structure is made up of a combination of different materials that are physically mixed together, rather than chemically bonded. This suggests that the structure is not a pure substance, but rather a mixture of different components.

When a line rotates clockwise from the initial line, it means that the angle formed is in the opposite direction of the positive angle. In geometry, angles can be measured in both positive and negative directions. Positive angles are measured counterclockwise, while negative angles are measured clockwise. Therefore, when the line rotates clockwise, it forms a negative angle.

Stainless steel is stabilized for use at high temperatures by adding columbium or titanium. These elements are added to stainless steel to improve its resistance to intergranular corrosion and sensitization, which can occur at high temperatures. Columbium and titanium form stable carbides, which help to prevent the formation of chromium carbides that can lead to sensitization and corrosion. This stabilization process ensures that the stainless steel maintains its mechanical properties and corrosion resistance even at elevated temperatures.

In grain refining case hardened steel, it is important to refine the core first. This is because the core is the innermost part of the steel and it plays a crucial role in providing strength and toughness to the material. By refining the core first, the grain structure in the innermost part of the steel can be improved, resulting in enhanced mechanical properties. Once the core is refined, the case can then be refined to further improve the surface hardness and wear resistance of the steel.

The test that involves the application of a slowly applied load along a sample's axis is called a tensile test. In this test, a sample is subjected to a gradually increasing load until it reaches its breaking point. The purpose of the test is to determine the strength and elasticity of the material being tested. By applying a load in tension, the test helps to measure the sample's ability to withstand stretching or pulling forces without breaking.

An oxidizing reactive atmosphere can lower cost because it reduces the reactivity of materials, which can prevent unwanted reactions and reduce the amount of waste or byproducts produced. This can lead to more efficient and cost-effective processes, as well as lower maintenance and cleanup costs. Additionally, by decreasing reactivity, an oxidizing reactive atmosphere can also increase the inertness of materials, making them more stable and less prone to degradation or corrosion. This can further contribute to cost savings by extending the lifespan of materials and reducing the need for replacements or repairs.

Cast iron contains more than 2% carbon (C), which is what differentiates it from cast steel. Cast steel, on the other hand, may also contain carbon, but it does not necessarily have to contain more than 2% carbon. This difference in carbon content affects the properties of the materials. Cast iron is known for its high carbon content, which makes it brittle and less malleable compared to cast steel. Cast steel, on the other hand, may have more hardening properties due to its carbon content, but it is generally more malleable than cast iron.

The choice of heating element depends on the function and atmosphere of the furnace. The function refers to the specific purpose or process that the furnace is designed for, such as melting, annealing, or heat treating. Different functions require different heating elements with varying temperature capabilities and heat distribution properties. The atmosphere refers to the gas or environment inside the furnace, which can be inert, oxidizing, or reducing. The choice of heating element also depends on the compatibility with the atmosphere to ensure optimal performance and longevity.

After solution heat treating, titanium alloys are often quenched in still air. This is because titanium has a high affinity for oxygen, and quenching in still air allows for controlled cooling and gradual reduction in temperature. Quenching in water, brine, or oil can result in rapid cooling and potential distortion or cracking of the material. Therefore, still air quenching is preferred to maintain the desired mechanical properties of the titanium alloy.

Successful solution heat treatment of heat treatable aluminum alloys requires trapping the copper in solid solution. This is because copper is an alloying element that can form precipitates during the heat treatment process, which can negatively affect the mechanical properties of the alloy. By trapping the copper in solid solution, it remains dissolved in the aluminum matrix and prevents the formation of these precipitates. This allows for improved strength and hardness properties in the final heat-treated alloy.

The time that a material remains in decalescence, which is the period during which the material is cooling and undergoing a phase transformation, is based on the metal's mass. The larger the mass of the metal, the longer it takes for the material to cool down and complete the phase transformation. Therefore, the mass of the metal directly affects the duration of decalescence.

Recalescence refers to the phenomenon in the heat treating process where there is a sudden liberation of heat without a drop in temperature. This can occur when the material undergoes a phase transformation, such as during the solidification of a molten metal or the crystallization of an alloy. The sudden release of heat during recalescence can have important implications for the heat treatment process, as it can affect the microstructure and properties of the material being treated.

Precipitation hardening stainless steels are different from austenitic stainless steels because they have a lower carbon content. This lower carbon content allows for the precipitation hardening process, where the steel is heat treated to form precipitates that increase its strength. Austenitic stainless steels, on the other hand, have higher carbon content which makes them non-hardenable by heat treatment.

Nickel or copper is most often used when pre-plating aluminum, steel, or brass. These materials are commonly chosen for their ability to provide a protective layer and enhance the appearance of the metal surface. Nickel plating offers excellent corrosion resistance and durability, making it suitable for various applications. Copper plating, on the other hand, is often used for its excellent conductivity and as an underlayer for other coatings. Both nickel and copper provide a good base for subsequent plating or finishing processes.

Annealing is the most common heat-treating procedure for titanium alloys. Annealing involves heating the material to a specific temperature and then slowly cooling it, which helps to remove internal stresses and improve the material's ductility and toughness. This process also helps to refine the grain structure of the alloy, making it more uniform and reducing the risk of cracking or failure. Additionally, annealing can help to restore the material's properties after it has been subjected to harsh conditions or extensive processing.

Annealing is the correct heat-treating procedure to improve machinability in titanium. Annealing involves heating the titanium to a specific temperature and then slowly cooling it down. This process helps to reduce the hardness and increase the ductility of the material, making it easier to machine. By annealing, the titanium undergoes a structural transformation that relieves internal stresses and enhances its workability.

Metal parts with uneven cross sections require slower heating rates because uneven cross sections can cause thermal stresses during the heating process. Slower heating rates allow for a more uniform temperature distribution throughout the part, reducing the likelihood of thermal stresses and potential deformation or cracking. By heating the part slowly, the temperature can gradually equalize, minimizing the temperature gradients and ensuring a more controlled and uniform heating process. This helps to maintain the structural integrity of the metal part and prevent any undesirable effects that may occur due to rapid or uneven heating.

Agitation is necessary during the quenching process to maintain contact between the part being quenched and the quenchant (liquid medium). This ensures that the heat is transferred evenly and efficiently from the part to the quenchant, allowing for a uniform cooling rate. By maintaining contact with the quenchant, the part is able to achieve the desired hardness and avoid the formation of hard spots or warpage. Additionally, agitation helps to prevent the formation of steam pockets, which could hinder the quenching process.

Decalescence refers to a phenomenon in which heated steel absorbs heat without a corresponding increase in temperature. This means that even though heat is being transferred to the steel, its temperature remains constant. This can occur when the steel undergoes a phase transformation at a specific temperature, such as the Ar1 point mentioned in the options. During this transformation, the absorbed heat is utilized to change the internal structure of the steel rather than raising its temperature. Therefore, the correct answer is that decalescence occurs when heated steel absorbs heat without a rise in temperature.

A thermocouple is the most accurate pyrometer used today on heat-treating furnaces. A thermocouple is a device that consists of two different metals joined together at one end. When there is a temperature difference between the two ends, it creates a voltage that can be measured. This voltage is proportional to the temperature, allowing the thermocouple to accurately measure the heat in the furnace. Other options like a millivoltmeter, potentiometer, or electronic devices may have their applications, but a thermocouple is specifically designed for accurate temperature measurement in high-temperature environments like heat-treating furnaces.

As the percentage of carbon increases in steels, the hardening temperature decreases. This is because carbon is a strong carbide former and it increases the hardenability of steel. As the carbon content increases, the steel can achieve the desired hardness at lower temperatures, reducing the need for high heat treatment temperatures. However, after a certain point, increasing the carbon content further does not significantly affect the hardenability, and the hardening temperature stabilizes. Therefore, the correct answer is decreases.

The cooling rate during annealing steel parts depends on the composition of the metal. Different metals have different thermal properties, such as their specific heat capacity and thermal conductivity, which affect how quickly they can dissipate heat. Therefore, the composition of the metal determines how fast or slow the steel part will cool down during the annealing process.

Metal products shaped by force while in the solid state are classified as cast. This refers to the process of casting, where molten metal is poured into a mold and allowed to solidify. The solidified metal takes the shape of the mold and forms the desired product. Casting is commonly used to create complex shapes and is suitable for both small and large-scale production. It is different from machining, which involves removing material from a solid block, and from molding, which typically involves shaping materials in a semi-solid or liquid state. Wrought refers to metal that has been worked or shaped by hammering or rolling when it is in a solid state.

Type I rotary flap would be the correct choice to peen an aluminum alloy surface. This type of rotary flap is specifically designed for softer materials like aluminum. It features a softer abrasive grit and a more flexible construction, making it ideal for achieving a smooth and even peening effect on the aluminum alloy surface. Types II, III, and IV are likely designed for different materials or purposes, and may not be as effective or suitable for peening aluminum alloy surfaces.

In the nitriding process, hardening and tempering are done last. This means that the material is first hardened and tempered through another method before undergoing nitriding. Nitriding is a surface hardening process that involves the diffusion of nitrogen into the material's surface to increase its hardness and wear resistance. By performing hardening and tempering last, the material is able to achieve the desired hardness and strength through another method before undergoing nitriding to further enhance its surface properties.

Heat treating of stainless steel involves heating the material to a specific temperature and then cooling it in a controlled manner to achieve desired properties. Warpage refers to the distortion or bending of the material during this process. By closely controlling the heat treatment, the chances of warpage occurring are reduced. Therefore, the correct answer is decreased warpage.