钠钙硅玻璃的网络联接程度对力学性能的影响

Effect of Network Connectivity on Mechanical Properties of Soda Lime Silica Glass

玻璃在室温下的粘性弛豫时间非常长,以至于很难检测到粘性流动,但在尖锐的金刚石压头下就可以很容易地实现永久性变形,通过维氏压痕测试对钠钙硅玻璃的裂纹萌生以及永久形变进行研究,玻璃在测试中产生的形变分为塑性(或剪切)流动和致密化两种不同的变形过程。塑性流动是物质的体积守恒位移,而致密化是非体积守恒的不可逆压缩。本工作利用压痕法测试了钠钙硅玻璃的力学性能,特别探讨了玻璃的网络联接程度和施加荷载对其形变和断裂行为的影响。研究结果表明,当网络联接程度较低(即非桥氧含量高)时,玻璃的原子堆积密度较大,摩尔体积相对较低,导致更高的弹性模量和泊松比,其硬度和脆性值也更高,而韧性值较低,抗开裂能力相对较弱;相反,网络联接程度较高时,在整个压痕过程中致密化占据优势,玻璃的致密化程度越高,其抗开裂能力越强,这反映在压痕经过退火处理后,其残留应力降低的程度越大。

The viscous relaxation time of glass at room temperature is too long that to detect the viscous flow.However,permanent deformation can be easily realized under sharp diamond indenter.Crack initiation and permanent deformation of soda lime silica glass were studied by using a Vickers indentation tester.The deformation of glass is divided into two deformation processes:plastic(or shear)flow and densification.Plastic flow is the volume conservative displacement of material,while densification is the irreversible compression of non-volume conservation.In this work,the mechanical properties of soda lime silica glass were tested by using indentation method,where the influence of the network connectivity and applied load on deformation and fracture behavior of the glass was emphasized.It is found that,when the network connectivity is sufficiently low(i.e.high content of non-bridging oxygen),the glass has high atomic packing density and low molar volume,resulting in high elastic modulus and Poisson's ratio,high hardness and brittleness,low toughness and weak cracking resistance.On the contrary,when the network connectivity is high,densification is the characteristic of the whole indentation process.The higher the degree of densification in the glass,the stronger the crack resistance the glass will have,which is reflected by the great reduction in the residual stress of the indentation after annealing treatment.