Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama, 240-8501, Japan.
Sci Rep. 2020 Nov 4;10(1):18990. doi: 10.1038/s41598-020-75552-1.
Bones of humans and animals combine two unique features, namely: they are brittle yet have a very high fracture toughness linked to the tortuosity of the crack path and they have the ability to repeatedly heal local fissures such that full recovery of overall mechanical properties is obtained even if the local bone structure is irreversibly changed by the healing process. Here it is demonstrated that TiAlC MAX phase metallo-ceramics also having a bone-like hierarchical microstructure and also failing along zig-zag fracture surfaces similarly demonstrate repeated full strength and toughness recovery at room temperature, even though the (high temperature) healing reaction involves the local formation of dense and brittle alumina within the crack. Full recovery of the fracture toughness depends on the healed zone thickness and process zone size formed in the alumina reaction product. A 3-dimensional finite element method (FEM) analysis of the data obtained from a newly designed wedge splitting test allowed full extraction of the local fracture properties of the healed cracks.
它们既易碎又具有非常高的断裂韧性，这与裂纹路径的曲折有关，并且它们具有反复愈合局部裂缝的能力，从而即使通过愈合过程使局部骨骼结构不可逆转地发生变化，也能获得整体机械性能的完全恢复。这里表明，具有类似骨骼分层微观结构的 TiAlC MAX 相金属陶瓷也沿着之字形断裂表面同样表现出在室温下的重复完全强度和韧性恢复，即使（高温）愈合反应涉及在裂纹内形成致密且易碎的氧化铝。断裂韧性的完全恢复取决于愈合区厚度和氧化铝反应产物中形成的过程区尺寸。通过新设计的楔形劈裂试验获得的数据的三维有限元方法 (FEM) 分析允许从愈合裂缝中完全提取局部断裂性能。
