Metal Institute and others have developed magnesium-based bionic materials with high damping, high energy absorption and shape memory

In addition to its high specific strength, specific stiffness and excellent thermal conductivity and electromagnetic shielding, magnesium has significantly better damping performance than most engineering metal materials and even can match some commonly used polymer materials, but its strength and heat resistance are significantly higher than those of polymer materials, thus highlighting its advantages in shock absorption, energy absorption and noise reduction. The strength, rigidity, plasticity and fracture toughness of magnesium and its alloys are still lower than those of steel and aluminum alloy, and their poor high temperature creep resistance restricts their wide application. As we all know, the strength and damping performance of metal materials show contradictory inverted relations. On the one hand, the strength can be improved by limiting the movement of dislocations, on the other hand, damping requires dislocations to move easily and get rid of pinning, which leads to relying on classical material strengthening methods at the expense of damping performance. How to realize the strengthening and toughening of magnesium and magnesium alloy without significantly increasing the density and reducing the damping performance has become a challenging key scientific problem.

Compared with artificial materials, the macro-mechanical properties of natural biomaterials are usually significantly better than the simple addition of their basic structural units. The origin lies in their complex and multi-scale self-assembly structures. Such as shells, bones and the like present a three-dimensional interpenetrating structure in microscopic, and each component phase remains connected and interpenetrated with each other, thus realizing the complementary advantages of each component phase in performance and function and the synchronous strengthening and toughening of materials. The understanding of the magical "structure-performance relationship" in nature provides a unique idea for the design of new materials with excellent comprehensive performance.

Recently, Aiming at the requirements of aerospace, precision instruments and other fields for material shock absorption, energy absorption and other aspects of performance, Liu Zenggan, Zhang Zhefeng, Laboratory of Material Fatigue and Fracture, Institute of Metals, Chinese Academy of Sciences, Li Shujun, Yang Rui and others from the Titanium Alloy Research Department cooperated with the University of California, Berkeley, and the China Institute of Engineering Physics to draw lessons from the concept of three-dimensional interpenetrating microstructure of natural biomaterials, and molten and infiltrated magnesium into the nickel-titanium alloy skeleton made of additives to build a light, high strength, high damping, and high energy absorption magnesium-nickel-titanium bionic composite material (see Figure 1).  

The microscopic three-dimensional interpenetrating bionic structure not only realizes the complementation and combination of nickel-titanium reinforced phase and magnesium matrix in performance advantages, but also endows the material with shape memory and self-repair functions. First of all, the interpenetration of the constituent phases in the three-dimensional space is conducive to promoting the stress transmission between each other, weakening the stress concentration, making the deformation of the two phases more coordinated, and better exerting the strengthening effect of nickel-titanium reinforced phases. The strength of bionic composite materials is significantly higher than that of simple superposition based on the mixing law (see Fig. 2). Secondly, the metallurgical bonding between matrix and reinforcing phase in bionic composites not only depends on the metallurgical bonding of the interface, but also has three-dimensional interlocking mechanical interlocking, which effectively avoids premature failure caused by interface cracking and endows the material with good damage tolerance. Thirdly, the three-dimensional penetration of the constituent phases in the bionic composite not only fully retains the damping performance of the magnesium matrix, but also the weak interface combination between the two phases can introduce new damping mechanisms such as micro-yield and micro-crack to further improve the damping performance. In addition, in a specific temperature range (> 150. Degree. C.), The shape memory effect of Ni-Ti reinforced phase skeleton is coupled with the creep behavior of Mg matrix, The recovery stress of nickel and titanium is much higher than the creep stress of the matrix, so that the bionic composite material after deformation damage can recover its initial shape and strength through conventional heat treatment, achieving the dual effects of shape memory with self-repair function, and can be recycled back and forth (see Fig. 3).

Through multiple mechanisms to improve the strength and damping performance respectively, The new bionic composite material breaks through the mutual restriction relationship between the two and realizes a good combination of various properties such as strength, damping and energy absorption efficiency of magnesium alloy. Its comprehensive performance is better than that of currently known engineering materials (see Fig. 4). It is expected to become a new damping and shock absorbing material required in precision instruments, aerospace and other fields.  

The above work was recently published in Science Advances  6 (2020) eaba5581, the first author of the article is Zhang Mingyang, PhD graduate student of the Institute of Metals. Relevant work is supported by the National Natural Science Foundation, the "Xingliao Talents Program" and the Key Research Program of Frontier Science of the Chinese Academy of Sciences.

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Fig. 1: Preparation process and microscopic three-dimensional interpenetrating bionic structure of a new magnesium-nickel-titanium bionic composite material

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Fig. 2: Compressive mechanical properties and damping properties of the new magnesium-nickel-titanium bionic composite and their comparison with each component phase

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Fig. 3: Shape memory function and microscopic recovery mechanism of a new magnesium-nickel-titanium bionic composite under different strain conditions

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Fig. 4: Comparison of strength, damping performance and energy absorption efficiency of the new magnesium-nickel-titanium bionic composite with other materials