Non-Hookean large elastic deformation in bulk crystalline metals

Abstract

Crystalline metals can have large theoretical elastic strain limits. However, a macroscopic block of conventional crystalline metals practically suffers a very limited elastic deformation of <0.5% with a linear stress–strain relationship obeying Hooke’s law. Here, we report on the experimental observation of a large tensile elastic deformation with an elastic strain of >4.3% in a Cu-based single crystalline alloy at its bulk scale at room temperature. The large macroscopic elastic strain that originates from the reversible lattice strain of a single phase is demonstrated by in situ microstructure and neutron diffraction observations. Furthermore, the elastic reversible deformation, which is nonhysteretic and quasilinear, is associated with a pronounced elastic softening phenomenon. The increase in the stress gives rise to a reduced Young’s modulus, unlike the traditional Hooke’s law behaviour. The experimental discovery of a non-Hookean large elastic deformation offers the potential for the development of bulk crystalline metals as high-performance mechanical springs or for new applications via “elastic strain engineering.”

Flexible molecular crystals for optoelectronic applications

“…22 However, the interest has been mostly limited to ionic crystals, 23,24 atomic crystals, 25,26 and metal crystals. 27 The mechanical flexiblility response of molecular crystals, reflected in their ability to undergo plastic shearing, plastic bending, or elastic bending (Fig. 1), has attracted wider attention over the past two decades.…”

Multifunctional High Entropy Alloys Enabled by Severe Lattice Distortion

“…increasing the degree of lattice distortion. [28,106] Moreover, it is worth pointing out that, unlike strain glass alloys, [117,118] lattice distortion-induced superelasticity in HEAs is strain rate independent. [28] In principle, decreasing structural defects with temperature increases elastic moduli, counteracting the decreasing moduli due to thermal expansion, resulting in temperature-independent elastic moduli (Elinvar effect) as seen in Figure 8b.…”

“…According to the Ashby plot shown in Figure a, conventional crystalline alloys typically have an elastic strain limit below 1% at room temperature due to the activation of crystalline defects such as dislocations. [ 106 ] In contrast, shape memory alloys, [ 107 ] strain glass alloys, [ 108–110 ] and Gum metals [ 111 ] can exhibit recovery strains of several percent. However, the superelasticity in these alloys originates from stress‐induced phase transformation (e.g., martensitic phase transition), which often involves significant energy dissipation or mechanical hysteresis, constraining their use in applications that require high energy storage efficiency.…”

“…[ 65,100 ] suggest that lattice distortion can reduce the elastic modulus while increasing the yield strength, an improved elastic strain limit could possibly be achieved through increasing the degree of lattice distortion. [ 28,106 ] Moreover, it is worth pointing out that, unlike strain glass alloys, [ 117,118 ] lattice distortion‐induced superelasticity in HEAs is strain rate independent. [ 28 ]…”

Investigation of Elastic Softening and Stiffening Effect of Aluminum Nitride Under Stress Loading by Born‐Lande Equation

“…On the other hand, elastic softening and stiffening effect under large stress loading has drawn tremendous attention in recent years, due to its great potential for intelligent mechanical structures [4,5]. From the perspective of elastic behavior, elastic softening and stiffening effect is a nonlinear elastic response in stress-strain relationships [6,7], which does not obey the traditional Hooke's law, indicating the coefficient of elasticity is not a constant, but a stress loading dependent physical parameter. In other words, large stress loading enables the modulation of coefficient of elasticity.…”