LibinLiu
Central South University, Changsha, Hunan 410083, P.R. China 

EXTENDED ABSTRACT: The CALPHAD method is currently the most widely used mesoscopic level material and process design method in the industry. This report introduces our recent work on advanced alloy and process design in titanium alloys, aluminum alloys, and steel using the CALPHAD method:
1. A database of thermodynamics and diffusion kinetics for Ti based alloys was developed. The mechanism of the formation of the powder boundary brittle phase during powder metallurgy of the Ti2A1Nb engine case and the formation of large thin plate borides during cast TiAl blade were successfully identified. Several high-strength Ti alloys were designed using pseudo-spinodal decomposition concept. By using a simple heat treatment process to modulate the internal composition distribution of the alloy, heterogeneous structures were formed in Ti5553 l alloy, and the simultaneous increase of material strength and plasticity was achieved.
2. A thermodynamic database of Al-Cu-Mg-Ag-Sc-Si-Zr-Mn was established. A heat-resistant aluminum alloy, with a tensile strength of 526士15 MPa, a yield strength of 487士13 MPa, an elongation of 8.2士0.5%, and a yield strength of 454士10 MPa even after l 00 hours of heat exposure at 200 ·c , has been designed. The mentioned properties is much higher than the that of the commonly used 2618 alloy.
3. The influence of alloy elements on the solubility of nitrogen in steel was calculated. Optimal nitriding processes for 304 and 254SMO were developed, which significantly improved the corrosion resistance of the stainless steels. The influence of Si on the stability of the ferrite phase during the cooling process of the valve steels was calculated, and the problem of insufficient surface quenching hardness during valve production was successfully solved.
The above research indicates that the CALPHAD method can provide important guidance for the development of new materials and processes, as well as for the optimization of the composition of existing alloy grades. Further innovation of the model, development of independent intellectual property CALPHAD calculation software, and establishment of more accurate databases for thermodynamics, mobility, and thermo-physical properties are key issue for fulfill the goal ofMGE.
Keywords: Heat-resistant Al alloys; Thermodynamics; CALPHAD; First-Principles calculations