Mechanical properties and microscopic structure analysis of 7005 alloys employed in-underground railway trains

The effects of the extrusion temperature, extrusion speed, quenching way and aging conditions on the mechanical properties of 7005 alloys were studied by the on-line extrusion experiments and transmitted electron microscopic analysis. The results show that reducing extrusion speed and quenching speed can improve the mechanical properties of the alloys to a certain extent, but the most obvious factors on the mechanical properties of the alloys are extrusion temperature and aging conditions. Higher mechanical properties can be acquired on lower extrusion temperature and shorter aging time. Transmitted electron microscopic analysis shows that η′ precipitated phase is smaller in size and evenly distributed and PFZ near grain boundary is narrow on lower extrusion temperature and shorter aging time, so the mechanical property of alloys can be improved. Overaging can be generated on higher extrusion temperature and longer aging time, and the coarse η′ precipitated phase distributed unevenly arises, which can result in worse mechanical property.