Microstructural and mechanical characterization of Nb-based in situ composites from Nb-Si-Ti ternary system
Microstructural and mechanical characterization of Nb-based in situ composites from Nb-Si-Ti ternary system
复制标题
Nb-Si-Ti 三元系铌基原位复合材料的微观结构和力学表征
DOI：
10.1016/j.actamat.2007.08.012
复制
发表时间：
2007-11-01
期刊：
影响因子：
9.4
通讯作者：
Peng, L. M.
中科院分区：
文献类型：
--
作者：
Li, Z.;Peng, L. M.
本文研究了用Nb-Si-Ti三元粉末混合物热压制备的Nb-铌硅化物基复合材料，其中Ti的添加量为6at.%和Si含量范围从过氧化氢（11 at.%）至近共晶组合物（18原子%）。研究了Si含量、Ti添加量和应变速率对试样微观组织、抗弯强度、断裂韧性、准静态压缩变形和破坏过程的影响。结果表明，硅化物的体积分数随Si含量的增加而增加，大部分Ti原子固溶于铌硅化物中形成（Nb，Ti）（5）Si-3固溶体，而不是二元钛硅化物。实验结果表明，Ti的加入使复合材料的抗弯强度、断裂韧性和压缩屈服应力得到适度的提高。较高的Si添加量产生了更显着的增强的压缩屈服应力和体硬度，而弯曲强度和断裂韧性随着Si含量的增加，由于在样品中的残余孔隙的存在而下降。复合材料的断裂韧性（8.3-13.0 MPa根m对4.5 MPa根m）明显优于未熔化的Nb-Si合金和整体铌硅化物，其增韧作用主要归因于残余韧性Nb相的裂纹桥接和裂纹偏转。此外，应变率在10（5）和10（3）S-1之间的准静态单轴压缩试验表明，Si含量和应变率对变形行为和破坏过程有显着影响。复合材料在所有应变速率下均表现出应变速率硬化行为，且应变速率敏感性随Si含量的增加而降低。在较低的应变速率下，具有亚共晶Si组合物的复合材料以假塑性响应并且以与压缩加载方向成近似45度的角度失效。而在较高应变速率和硅含量下，试样的脆性破坏主要是通过碎片的垂直劈裂和剥落实现的。(c)2007 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
This study deals with the Nb-niobium silicide-based composites developed by the hot-pressing of Nb-Si-Ti ternary powder mixtures with a fixed Ti addition (6 at.%) and Si content ranging from hypereutectic (I I at.%) to near-eutectic compositions (18 at.%). The effects of Si content, Ti addition and strain rates on the sample microstructural characterization, flexural strength, fracture toughness, quasistatic compressive deformation and failure processes were investigated. It was revealed that the volume fraction of silicides increased with increasing Si content, and most of the Ti atoms dissolved into the niobium silicides to form (Nb,Ti)(5)Si-3 solid solutions instead of binary titanium silicides. The experimental evidence showed that a moderate improvement in the flexural strength, fracture toughness and compressive yield stress of the composites was achieved by the addition of Ti. Higher Si additions produced a much more remarkable enhancement in the compressive yield stress and bulk hardness, whereas both the flexural strength and fracture toughness decreased with increasing Si content owing to the existence of residual porosities in the samples. The composites showed remarkable superiority to the are-melted Nb-Si alloys and monolithic niobium silicides in fracture toughness (8.3-13.0 MPa root m vs. 4.5 MPa root m), where the toughening effect was attributed mainly to crack bridging and crack deflection by the remaining ductile Nb phase. Moreover, quasi-static uniaxial compression tests at strain rates between 10 (5) and 10 (3) S-1 indicated that the deformation behavior and failure processes were significantly affected by Si content and strain rates. The strain-rate-hardening behavior for all the strain rates was observed in the composite materials and the strain-rate sensitivity decreased with increasing Si content. At a lower strain rate, the composite materials with a hypoeutectic Si composition failed with a pseudoplastic response and at an angle of similar to 45 degrees off the compressive loading direction. However, in the case of higher strain rate and Si content, the brittle failure in the samples occurred through vertical splitting and spalling of fragments. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.