钨纤维/钨复合材料的断裂行为及热冲击损伤分析

Fracture behavior and transient thermal shock damage analysis of tungsten fiber/tungsten composites

摘要:

自纤维增韧是改善钨材脆性的一种有效途径。本文采用放电等离子体烧结技术制备了以难熔金属钼为界面涂层的连续钨纤维增韧钨复合材料，研究复合材料拉伸脆-韧转变温度，分析和探讨钼涂层在复合材料断裂中的作用以及对Wf/W复合材料断裂模式的影响。结果表明：复合材料在400℃及以下均发生拉伸脆断，但从400℃开始，纤维与基体界面区域出现多条曲形裂纹，涂层有减弱钨基体和钨纤维界面结合强度的迹象。500℃时复合材料出现韧性断裂，韧性主要来源于纤维带来的伪韧性。钼作为界面涂层有助于发动纤维脱粘-韧断增韧机制，但涂层本身由于特殊结构取向并无预期的钼塑性变形带来增韧贡献。对纤维和粗晶结构钨材料的耐瞬态热冲击性能进行分析，高强韧、低DBTT的钨纤维比粗晶钨基体更能抗热冲击，纤维复合材料可以减少开裂区域。

关键词:钨纤维，界面涂层，Wf/W复合材料，放电等离子体烧结, 瞬态热冲击

Abstract:

Tungsten-fiber toughening is an effective way to improve the brittleness of tungsten materials. In this paper, a continuous tungsten fibers-toughened tungsten composite with refractory metal molybdenum as the interfacial coating was prepared by spark plasma sintering technology. The tensile brittle-to-ductile transition temperature of the composite was studied, and the influence of molybdenum coating on the fracture mode of the Wf/W composite were analyzed and discussed. The tensile test results show that the composite is brittle fracture at 400℃ and below. Many curved cracks are formed until 400℃ at the interface between fibers and matrix, indicating that the coating has signs of weakening the bonding strength of the matrix-fiber interfaces. The composite exhibits toughness at 500°C, which mainly comes from the pseudo-plasticity by fibers. Molybdenum as an interfacial coating helps to stimulate the fiber debonding-fracture toughening mechanism. However, due to the special structural orientation of the coating by magnetron sputtering, there is no expected plastic deformation of molybdenum. The transient thermal shock resistance of fibers and coarse-grained tungsten were analyzed. Tungsten fibers were more resistant to thermal shock than coarse-grained tungsten matrix due to high strength and low DBTT, and incorporation of fiber could reduce cracking areas of tungsten materials.

Key words:Tungsten fiber; Interfacial coating; Wf/W composite; Spark plasma sintering;Transient thermal shock