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To study the scratch effect on the metal corrosion, some special scratches on the Cr-Mn ferroalloy were formed by rubbing a sandpaper on the sample surface. Two environmental cases are considered, that is, a humidity air, and a humidity air bottomed with alkaline–organic solution successively. The micro-surfaces of the samples are observed by Energy dispersive spectrometer, and the elementary contents are analyzed on an area and a line. Special scratches on the surface of Cr-Mn ferroalloy do not accelerate the metal corrosion in a humid organic alkaline environment. On the contrary, it would play a positive role in the sample passive anti-corrosion process. Chromium oxide and manganese oxide particles are produced by the oxidation of metals in a humidity air would gather in the grooves caused by the scratches. The relative study is less reported till now.

The bonding between copper (Cu) and iron (Fe) to form a bi-layer composite using explosive welding is investigated through molecular dynamics simulation. Three stages in the joining process, including loading, unloading and cooling, are sequentially considered in modelling the formation of the bonding interface. The results demonstrate that three types of bonding interfaces can be obtained, based on whether melting happens. The morphologies and the atomic structures of the three types bonding interfaces in each stage are analyzed. The formation of nanograins near the bonding interface is mainly due to the melting and subsequent cooling process. Atomic simulations of tensile tests reveal that melting is not a necessary factor to form the bonding interface. What's more, depending on whether melting occurs, the joining mechanism can be regarded as pressure welding or fusion-diffusion welding.