Wang Haiyun, Chen Na, Cheng Huanwu, Wang Yangwei, Zhao Denghui
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
China Ordnance Industrial Standardization Research Institute, Beijing 100089, China.
Materials (Basel). 2024 Sep 12;17(18):4486. doi: 10.3390/ma17184486.
Ti-based bulk metallic glass composites (BMGMCs) containing an formed metastable β phase normally exhibit enhanced plasticity attributed to induced phase transformation or twinning. However, the underlying deformation micromechanism remains controversial. This study investigates a novel deformation mechanism of Ti-based BMGMCs with a composition of TiZrCuNbNiBe (at%). The microstructures after tension were analyzed using advanced electron microscopy. The dendrites were homogeneously distributed in the glassy matrix with a volume fraction of 55 ± 2% and a size of 1~5 μm. The BMGMCs deformed in a serrated manner with a fracture strength (σ) of ~1710 MPa and a fracture strain of ~7.1%, accompanying strain hardening. The plastic deformation beyond yielding was achieved by a synergistic action, which includes shear banding, localized amorphization and a localized BCC (β-Ti) to HCP (α-Ti) structural transition. The localized amorphization was caused by high local strain rates during shear band extension from the amorphous matrix to the crystalline reinforcements. The localized structural transition from BCC to HCP resulted from accumulating concentrated stress during deformation. The synergistic action enriches our understanding of the deformation mechanism of Ti-based BMGMCs and also sheds light on material design and performance improvement.
含有形成的亚稳β相的钛基块状金属玻璃复合材料（BMGMCs）通常由于诱导相变或孪生而表现出增强的塑性。然而，其潜在的变形微观机制仍存在争议。本研究调查了一种成分（原子百分比）为TiZrCuNbNiBe的钛基BMGMCs的新型变形机制。使用先进的电子显微镜分析了拉伸后的微观结构。枝晶均匀分布在玻璃基体中，体积分数为55±2%，尺寸为1~5μm。BMGMCs以锯齿状方式变形，断裂强度（σ）约为1710MPa，断裂应变为约7.1%，伴有应变硬化。屈服后的塑性变形是通过协同作用实现的，包括剪切带形成、局部非晶化以及从局部体心立方（β-Ti）到六方密排（α-Ti）的结构转变。局部非晶化是由剪切带从非晶基体延伸到晶体增强相时的高局部应变速率引起的。从体心立方到六方密排的局部结构转变是由变形过程中累积的集中应力导致的。这种协同作用丰富了我们对钛基BMGMCs变形机制的理解，也为材料设计和性能改进提供了思路。
