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通过改变熔模铸造用硅酸铝纤维复合型壳的焙烧温度和保温时间等焙烧工艺,研究其抗弯强度的变化规律。利用SEM对弯曲断裂型壳试样的断口形貌进行观察。实验结果表明,纤维增强型壳的焙烧后抗弯强度提高,在焙烧温度为925℃时达到最大,为3.8 MPa。焙烧温度为950℃时,焙烧后强度随保温时间延长而增大,保温时间为120 min时最大,随后有所降低。断口SEM观察表明,硅酸铝纤维主要依靠其变形和断裂分担载荷。
The changing law of flexural strength was studied by changing the roasting process such as calcination temperature and holding time of the aluminum silicate fiber composite shell for investment casting. The fracture morphology of bent fracture shell specimens was observed by SEM. The experimental results show that the flexural strength of the fiber reinforced shell increases after roasting, reaching the maximum of 3.8 MPa at the calcination temperature of 925 ℃. When the calcination temperature is 950 ℃, the strength increases with the prolongation of holding time and the holding time reaches the maximum at 120 min, then decreases. SEM observation of fracture shows that aluminum silicate fiber mainly relies on its deformation and fracture load sharing.