The press hardening steel with thick specification has been used as automobile chassis parts. With the increase of the thickness, the cooling rate of the inner core is lower in the conventional process, resulting in a poor harden ability, and the fatigue test is not qualified. In this study, the microstructure of hot forming parts with thick specifications was studied by means of metallographic and micro-hardness testing. The results show that there is a microstructure gradient in the thick hot forming parts, which leads to the uneven strength in the cross section and finally affects the fatigue test results.The finite element analysis method is used to study the cooling rate of the inner core of the hot forming parts. The high hardenability press hardening steel products has been prepared by adjusting the components.

Microstructure and mechanical properties of zirconia-toughened alumina (ZTA) composite ceramics prepared by gelcasting process were investigated. The results indicated that Al2O3-ZrO2 composites have high bending strength and fracture toughness for the solid loading of the suspension ³ 50vol.%. The bending strength and fracture toughness of sintered ZTA ceramics reach values as high as 631.5 MPa and 7.64 MPa·m1/2, respectively, with solid loading of suspension being 55vol.%. The t-ZrO2 content is increased, and the uniformity of ZrO2 particle distribution is improved in sintered samples prepared by gelcasting compared with those by dry pressing.