Mechanical properties of nickel-based alloys

Nickel-based alloys are alloys composed of nickel as the matrix (with a content generally greater than 50%) and the addition of one or several other elements. It has a series of excellent mechanical properties, as follows:
1. High strength: Nickel-based alloys can achieve high strength through alloying and heat treatment. In high-temperature environments, it can maintain better strength than many other alloys. For example, in high-temperature components such as aero engines, nickel-based alloys can withstand relatively large working stresses without excessive deformation or fracture. This is mainly attributed to the strengthening phases formed by elements such as chromium, molybdenum and niobium added to the alloy, which can hinder dislocation movement, enhance lattice resistance and effectively improve the strength of the alloy.
2. Good plasticity and toughness: Although nickel-based alloys have relatively high strength, they still possess certain plasticity and toughness. At normal temperature and some low-temperature environments, the alloy can withstand a certain degree of deformation without cracking. For instance, when manufacturing some complex-shaped components, alloys can be shaped through processing techniques such as forging and rolling to meet different production requirements. The excellent plasticity and toughness of nickel stem from its face-centered cubic lattice structure. This structure ensures a high degree of coordination among alloy atoms, facilitating their relative sliding under external forces and preventing brittle failure.
3. Good high-temperature creep performance: High-temperature creep refers to the phenomenon where metals slowly undergo plastic deformation under the action of high temperature for a long time and constant stress. Nickel-based alloys perform outstandingly in this aspect. Under extreme working conditions of high temperature and high stress, their creep rate is relatively low. For instance, in components that operate at high temperatures for long periods in fields such as petrochemicals and gas turbines, nickel-based alloys can ensure that the components maintain dimensional stability and undergo minimal shape changes within the specified service life. The alloy contains trace elements such as boron and zirconium, which can effectively strengthen the grain boundaries, slow down the sliding and diffusion of the grain boundaries, and thereby improve the creep resistance of the alloy.
4. Excellent fatigue performance: When subjected to alternating stress, nickel-based alloys have a relatively good fatigue life. In some components that are frequently subjected to cyclic loads, such as aircraft landing gears and engine blades, fatigue cracks are not prone to occur prematurely due to the continuous accumulation of fatigue stress. The uniformity of the alloy's own microstructure reduces local stress concentration points. Coupled with its excellent microstructure stability, nickel-based alloys can operate stably for a long time under alternating stress, significantly reducing the risk of fatigue failure.
5. High fracture toughness: Even in the presence of crack defects, nickel-based alloys demonstrate excellent crack propagation resistance and have high fracture toughness. For instance, under working conditions where minor manufacturing defects may occur or cracks may develop during later use, nickel-based alloy components will not suddenly suffer catastrophic fractures due to the rapid expansion of cracks, which ensures the safety and reliability of component operation. The good bonding state between alloying elements and the nickel matrix, as well as the reasonable microstructure, increase the resistance to crack propagation and are important reasons for the high fracture toughness.

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