钛基双相非晶设计实现力学性能突破

Titanium-Based Biphase Amorphous Design Achieves Breakthrough in Mechanical Properties

摘要: 目前，微机电系统(MEMS)在航空航天、电力电子及生物医学领域的广泛应用对材料力学性能提出更高要求，而传统Ti基合金难以满足严苛服役环境。非晶合金因缺乏晶界和位错等晶体缺陷，具备优异机械性能，但其塑性不足严重限制了实际应用。为此，我们开发了一种新型“可控微结构编程”策略，通过在Ti合金中引入具有高正混合焓和大原子尺寸失配的镱(Yb)元素，结合磁控溅射技术的高冷却速率特性，实现对Ti基微观结构的精确调控，成功制备出双相非晶结构的TiYb合金薄膜。该材料表现出超越晶态薄膜的优异力学性能：(1) 超高硬度：硬度达7.8 GPa，弹性模量达163 GPa；(2) 均匀塑性变形能力：平滑的加载曲线表明多重剪切带激活，有效避免非晶材料的脆性失效。性能提升机制源于双相协同作用：强度提升归因于富Yb非晶相的高硬度和强度抑制了单一剪切带的扩展；塑性改善：较软的富Ti非晶相为剪切转变区(STZs)和胚胎剪切带提供形核位点，促进多重剪切带在应力下持续演化，显著增强塑性流动能力。本研究为Ti基薄膜体系提供了创新设计思路，并为高性能MEMS器件开发了极具潜力的候选材料。

Abstract: The proliferating deployment of micro-electromechanical systems (MEMS) in aerospace, power electronics, and biomedical sectors imposes rigorous mechanical demands on structural materials, which conventional Ti-based alloys increasingly fail to meet under stringent service conditions. Although amorphous alloys exhibit superior mechanical properties due to the absence of crystalline defects (e.g., grain boundaries and dislocations), their intrinsic plasticity deficit critically constrains practical implementation. To address this limitation, we devised a “controlled microstructure programming” strategy. By introducing ytterbium (Yb)—an element with high positive mixing enthalpy and significant atomic size mismatch—into Ti alloys and exploiting the ultrahigh cooling rates intrinsic to magnetron sputtering, we achieved atomic-level microstructural control, fabricating TiYb thin films with a biphase amorphous architecture. The resultant material demonstrates exceptional mechanical properties transcending crystalline film benchmarks: (1) Ultrahigh hardness (7.8 GPa) and elastic modulus (163 GPa); (2) Homogeneous plastic deformation manifested by smooth loading curves, confirming activation of multiple shear bands that effectively suppress the characteristic brittle fracture of amorphous materials. This performance enhancement originates from biphase synergy: Enhanced strength stems from the Yb-rich amorphous phase impeding single shear-band propagation via its inherent high hardness/strength; plasticity improvement arises as the softer Ti-rich amorphous phase nucleates shear transformation zones (STZs) and embryonic shear bands, driving sustained evolution of multiple shear bands under stress and substantially augmenting plastic flow capacity. This work establishes a pioneering design paradigm for Ti-based thin-film systems and delivers a high-potential candidate material for next-generation MEMS devices demanding extreme mechanical reliability.