纤维增强熔模铸造复合型壳的性能及断口形貌

为提高熔模铸造硅溶胶型壳的强度性能,采用天然植物/硅酸铝双纤维来增强熔模铸造型壳.将质量比为1:1天然植物/硅酸铝双纤维加入到制壳用涂料中来制备型壳试样,对不同纤维加入量条件下所获得的纤维增强型壳试样的常温强度、不同温度焙烧后的抗弯强度及高温自重变形量的变化规律进行了研究,并利用SEM观察型壳试样断口形貌.结果表明,当纤维加入量从0.2%逐渐增加到1.0%时,其常温抗弯强度先增加后减小;纤维加入量为0.6%时其常温抗弯强度值达到2.94 MPa.高温自重变形量则先减小后增大.加入0.6%纤维的增强型壳试样经900℃焙烧后,其抗弯强度达4.04 MPa,与未采用纤维增强的型壳试样的抗弯强度接近.断口形貌观察结果表明,纤维增强硅溶胶型壳试样受力破坏失效主要由于硅溶胶凝胶膜的断裂、硅酸铝纤维拔出、断裂及脱粘等综合作用所致.

Properties and fracture surface morphology of fiber-reinforced shell for investment casting

In order to improve the properties of silicon sol shell for investment casting process, natural plant fibers combined with aluminum silicate fibers at natural-to-aluminum silicate fibers mass ratio of 1:1 were mixed into the slurries preparing for fiber-reinforced shell. The flexural strength of specimens of green shells, fired shells at different temperatures and the self-loaded deformation of the latter at elevated temperature were investigated. The fracture surface of shell specimens was observed by SEM. The results show that the green strength of shell specimens increases firstly and then decreases with variation of content of fiber from 0.2% to 1.0%. However, the self-loaded deformation at elevated temperature firstly decreases and then increases. The green strength of shell specimens reinforced with 0.6% fibers reaches the maximum of 2.94 MPa. The bending strength of shell specimens reinforced with 0.6% fibers fired at 900℃ reaches 4.04 MPa, approaching that of the non-reinforced shell specimens. It is found by SEM that the failure of the fiber-reinforced shell specimens at the applied load is resulted in breakdown of silicon sol films and pulling-out, fracturing and debonding of fibers in the shell.