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In this article, the mechanism of the effects of nano-TiO2 on the properties of automotive topcoat is discussed. Based on the original thought that nano-TiO2 may improve the aging property, a research is carried out into the effects of nano-TiO2 on the properties of automotive topcoat, and the formulation design of nano-TiO2 coating is optimized. The coating properties such as glossiness, adhesion, resisting impact strength, hardness, water fastness and resistance to aging are measured by experiments. The results show that with 1.0~2.0 percent of nano-TiO2 content, the aging resistance of the coating increases by approximaSubscript texttely 20 percent with higher glossiness, while adhesion, impact strength, hardness and water fastness are not meaningfully improved.

The objective of this study is to determine the mechanism of the dramatic increase of impact toughness at low temperatures after post-weld heat treatment on weld joints. In this study, weld joints using two semi-automatic welding consumables were fabricated by flux cored arc welding with subsequent PWHT at 660°C for 65 min and 195 min, respectively. Tests of the tensile and yield strength, microhardness and impact toughness, were carried out. The microstructure was inspected by optical, scanning electron, and transmission electron microscopy in addition to compositional analysis using energy dispersive spectrometry. PWHT was observed to result in grain coarsening, sub-grain structure formation and decrease of the dislocation density. The increase of impact toughness is attributed to the relieved thermal stress, the inclusions and precipitations, softening of the structure, dislocation recovery and sub-grain structure.

In Zr-Cu-Ni-Al bulk metallic glasses where there are no dislocations, localized plastic deformation in shear bands occurs largely by the formation and migration of defects such as voids, micropores, shear bands and local variations in composition. Thus, the investigation on defects is critical for the understanding and improvement of plastic deformation in metallic glasses. In this study, microstructures and nano defects in the Zr-Cu-Ni-Al BMGs are characterized by variety of techniques, such as X-ray diffractometry, high resolution transmission electron microscopy, scanning transmission electron microscopy and electron holography.