Search

Although Ti2AX has excellent mechanical properties of both metals and ceramics, there are few papers exploring the correlation between mechanics and thermodynamics simultaneously. In this paper, the structure properties, elastic anisotropies, thermodynamic and tensile properties of Ti2AX (A = Al and Ga, X = C and N) MAX phases are studied by first-principles calculations. The results show that these MAX phases have thermodynamical, dynamical, and mechanical stabilities. The calculated anisotropy indexes indicate that the MAX phases are anisotropic in elastic modulus. Ti-X chemical bonds possess covalent-ionic mixed nature. Moreover, the sound velocities and thermal conductivities of these Ti2AX MAX phases are also anisotropic. According to the tensile calculation, the tensile strength along the [110] direction is greater than that along the [001] direction, and fracture failure will occur in the [110] direction. [ABSTRACT FROM AUTHOR]

Cast iron with good mechanical and thermal combination property is preferred material for the cylinder head of high power density diesel engine. Interface between graphite and matrix should play a key role in thermal conductivity of cast iron. However, it is difficult to measure the interfacial contact thermal conductance (ICTC) between graphite inclusion and matrix in cast iron. In this paper, a modeling experimental sample containing a macroscopic interface is designed and ICTC can be estimated with the aid of finite element (FE) calculation. At last the effect of ICTC on the thermal conductivity of cast iron is assessed according to the change of metallographic FE simulation results before and after considering ICTC. Results show that the magnitude of ICTC is between 1.0 × 105 and 2.0 × 105 W m−2·K on the whole. The interface makes the theoretical thermal conductivity of cast iron drop down 34.6%. [ABSTRACT FROM AUTHOR]

As an ideal material for the cylinder head of high power density diesel engine, vermicular graphite cast iron (VGI) with higher thermal conductivity was received more and more attention recently. In this article, finite element (FE) software ANSYS was applied to investigate the changes of thermal conductivity of VGI with the vermicularity and the FE-models are carried out based on the real metallographic images of VGI. The results indicate that there is a big difference between the numerical simulation and the reality without the consideration of the thermal contact resistance of interface between matrix and graphite. The numerical simulation result is close to the reality when the contact thermal conductance is set at 0.1 W/(m²K). In addition, the equivalent thermal conductivity along X direction kequ,x rises from 34.437 W/mK to 38.902 W/mK and increases by 13% or so when the vermicularity is improved from 40% to 90% according to the numerical simulation. [ABSTRACT FROM AUTHOR]