SiC泡沫陶瓷/Fe基双连续相复合材料的制备和性能

Preparation and Performance of SiC Foam Ceramic/Fe Matrix Co-continuous Phase Composites

将SiC泡沫陶瓷氧化,用挤压铸造法制备SiC泡沫陶瓷/Fe基双连续相复合材料并对其退火,研究了制备工艺和SiC泡沫陶瓷的体积分数对其微观组织和力学性能的影响。结果表明,在1250℃氧化48 h后在SiC泡沫陶瓷表面生成了厚度为1 mm的SiO2反应阻挡层。在双连续相复合材料的制备过程中,SiO2反应阻挡层抑制Fe与SiC的化学反应,避免了脆性化合物Fe3Si的生成,改善了基体与增强体的界面,使复合材料的抗弯强度提高2倍,压缩强度提高18%。当SiC泡沫陶瓷的氧化时间增至72 h时,SiC泡沫陶瓷表面SiO2的厚度过大。SiO2与基体和增强体热膨胀系数不匹配,使复合材料内相界面间的残余应力增加,导致其性能下降。将SiC泡沫陶瓷/Fe基双连续相复合材料在600℃退火4 h,可降低复合材料中的残余应力,提高复合材料的性能。SiC的体积分数较低时,金属基体的桥接、偏转裂纹的作用比较大,复合材料的弯曲强度高,变形程度大。随着复合材料中SiC体积分数的增大,SiC骨架筋增粗,其承载能力加强,复合材料的压缩强度呈提高的趋势。

SiC foam ceramic/Fe based co-continuous phase composites were prepared by squeeze casting method using oxidized SiC foam ceramic.Then the prepared composites were annealed.The influence of preparation process and SiC volume fraction on microstructures and mechanical properties of the composites were investigated.Results show that a SiO2 barrier film of 1 mm in thickness on the surfaces of SiC foam can form after oxidizing at 1250°C for 48 h,which then can efficiently prevent the formation of a brittle intermetallic compound Fe3 Si at the interface of Fe matrix and SiC during the preparation of composites.As a result,the flexural strength of composites was increased by 100% and compressive strength by 18%.The thickness of SiO2 film was increased after oxidizing at 1250°C for 72 h,and a thicker SiO2 film may induce mismatch of thermal expansion coefficient between SiO2,Fe and SiC,which thereby resulted in the increase of residual stress.Therefore,the mechanical properties of composites were decreased slightly.The residual stress could be relieved after annealing of composites at 600°C for4 h,which improved the mechanical properties of composites.The function of bridging and deflecting crack of metal matrix is big for the composite with small SiC volume fraction,which is in turn beneficial to the enhancement of the flexural strength and flexural strain.For the composite with the higher SiC volume fraction,the size of SiC skeleton became bigger and the load- carrying capacity was strengthened,thereby its compressive strength was increased.