Predicting final stage sintering grain growth affected by porosity

Abstract

Grain growth has a definitive impact on the quality of transparent sintered materials in areas such as ballistics, biomaterials, jewelry, etc. Controlling the sintering trajectory at the precise moment of final stage sintering is one of the main sintering challenges for obtaining highperformance, fully-dense nano-ceramics. However, the final stage of sintering involves a very complex coupling between the rate of porosity elimination/grain growth and transition mechanisms. This complexity makes predicting the sintering trajectory very difficult, and most transparent material production escapes this problem by using expensive high-pressure methods such as hot isostatic pressing (HIP). In the quest for a pressureless transparent material process, this paper addresses the challenge of predicting grain growth in the transition domain from the grain growth onset (in a high porosity region) to full density for MgAl 2 O 4 spinel. We present a comprehensive modeling approach linking theoretical models such as Zhao & Harmer's and Olevsky's equations to accurately predict the complex grain growth transition region of final stage sintering. This modeling approach opens up the possibility for numerical exploration of microstructure development via underlying kinetics experimental identification.

Modeling the sintering trajectories of MgAl2O4 Spinel

“…Similar approaches have been used for alumina [20], Zpex smile Tosoh zirconia [18], and also applied to spark plasma sintering with a relevant model [21]. This model will take into account the transition of grain growth mechanism from surface diffusion for high porosity content, to lattice diffusion for low porosity, as previously shown for this material [22]. Furthermore, it will be shown that the final stage grain growth mechanism transition is accompanied by a densification behavior transition.…”

“…𝐺 0 𝑚 ~𝐺0 . However, in this work, the grain growth parameters (see Equation (3) originated from ref [28]) are known as they were determined in our previous study ref [22].…”

“…In order to explore the grain growth behaviors in isothermal regime, twelves interrupted experiments at 1673, 1773, 1873 K (Figure 1. d,e,f) were conducted in a previous study [22]. In this work, these data will be employed as final validation of the experimental/modeled sintering trajectories and for adjusting the model parameters.…”

“…Latter validation step will be referred as "step 2". the interruptions [22]), e) porosity evolution during sintering, f) grain size evolution with dwelling time.…”

Porous stage assessment of pressure assisted sintering modeling parameters: a ceramic identification method insensitive to final stage grain growth disturbance

“…Sintering models should reflect numerous underlying phenomena competing to each other and requiring an extensive experimental identification of parameters which are temperature and porosity dependent. These phenomena are the densification vs grain growth [23,24], the pore coarsening by surface diffusion [25], the changes of sintering mechanisms [2,26], etc. For ceramics, the equivalent creep behavior is an important underlying dense phase phenomena governing the densification kinetics.…”