High-strength metals with polymer-level compliance (i.e., ultralow modulus) are critical for advancing transformative technologies such as morphing aircraft, soft robots, and implantable medical devices[1]. However, the inherent physical trade-off between strength and compliance has long been a fundamental bottleneck in material design, as conventional metallic systems have failed to simultaneously achieve steel-like ultrahigh strength and polymer-like ultralow modulus.

Herein, we report a novel Dual-Seed Strain Glass (DS-STG) alloy that exhibits an ultrahigh strength of σy≈1.8 GPa, a polymer-like ultralow modulus of E≈10.5 GPa, and a rubber-like reversible elastic strain of ~8%, yielding a remarkably high flexibility figure of merit (σy/E≈0.17) that far exceeds those of existing structural materials. Moreover, this exceptional performance is stable over a wide temperature range of −80 °C to +80 °C, and the alloy displays excellent fatigue resistance.

We fabricate the DS-STG alloy via a simple three-step thermomechanical treatment, which creates a unique microstructure featuring a long-range disordered strain glass matrix embedded with sparse, aligned R and B19′ martensite seeds. Deformation strengthening from processing imparts ultrahigh strength to the alloy, while a nucleation-free reversible transition between strain glass and B19’ martensite under external fields enables polymer-like low-modulus and fully reversible large-strain output, thus realizing the synergetic integration of ultrahigh strength and ultrahigh compliance.

The DS-STG alloy enriches the exotic property of strain glass alloys and establishes a new paradigm for designing high-performance flexible metallic materials. Its “strain glass matrix + martensite seeds” structural design strategy is extendable to ferromagnetic shape memory alloy systems, holding great promise for creating novel multifunctional strain glass alloys that integrate ultrahigh strength, ultralow modulus, and superior magnetic response, thereby driving a leap forward in advanced flexible metallic materials.

Dr. Zhizhi Xu