Al_(2)O_(3)-SiO_(2)非晶陶瓷中温塑性变形研究

Plastic Deformation of Amorphous Al_(2)O_(3)-SiO_(2) at Moderate-Temperature

解决陶瓷脆性、实现陶瓷的塑性变形是诸多尖端领域发展的关键。为探究Al_(2)O_(3)-SiO_(2)非晶陶瓷的中温塑性变形,利用溶胶凝胶法和热压成形技术制备具有非晶结构的致密Al_(2)O_(3)-SiO_(2)陶瓷块体,在600~800℃进行单轴压缩测试。Al_(2)O_(3)-SiO_(2)非晶陶瓷在600℃脆性断裂前未能发生塑性变形,在700℃、800℃分别呈现9.9%和12.8%的塑性变形,而且在800℃的塑性变形中析出γ-Al_(2)O_(3)晶相并产生应变强化。不同于Al_(2)O_(3)-SiO_(2)非晶陶瓷,同组成的多晶陶瓷在800℃仍然表现脆性而无塑性变形。利用自由体积理论对非晶陶瓷的塑性变形机理进行了探究,剪切带是塑性变形的主要方式,而自由体积是形成剪切带的结构基础。这种可塑性变形的非晶陶瓷材料由于具有耐高温、耐腐蚀以及良好的塑性变形,在冶金铸造系统的密封结构中具有潜在优势。

Solving the brittleness and achieving the plasticity of ceramics are the key factors to development of various frontier domains.To explore the moderate-temperature plastic deformation in amorphous Al_(2)O_(3)-SiO_(2)ceramcis,dense ceramics with homogenous amorphous structure were prepared by sol-gel method along with hot pressing,which was then tested under uniaxial compression at 600-800℃.The amorphous Al_(2)O_(3)-SiO_(2)ceramcis exhibited no plastic deformation before brittle fracture at 600℃,and showed significant plastic deformation of 9.9%and 12.8% at 700℃and 800℃,respectively.Moreover,during the plastic deformation at 800℃,crystallization of γ-Al_(2)O_(3)was exhibited and leaded to strain hardening.Compared to the amorphous ceramics,the polycrystal Al_(2)O_(3)-SiO_(2)ceramics with the same composition displayed brittle fracture without any plastic deformation.The mechanism of plastic deformation was explored by free volume theory,in which shear bands are the major mode in deformation and the free volumes are the structural foundation for shear bands.These plastically deformable amorphous ceramics have potential advantages in high-tech fields including aerospace and metallurgical casting.