Effect of Cold DeformationProperties of Aluminum Material
2019-03-05人閱讀
A: Physical and chemical properties.
1) Density. After cold deformation, the density of aluminium decreases due to the appearance of micro-cracks or macro-cracks, crack holes and other defects within and between grains.
2) Resistance. The direct contact of grains, the ordering of grain orientation, the intergranular and intragranular ruptures caused by the destruction of intergranular materials have obvious effects on the change of resistance. The former makes the resistance decrease with the increase of deformation degree, while the latter makes the opposite.
3) Chemical stability. After cold deformation, the internal energy of the material increases, which makes its chemical properties more unstable and easy to be corroded, especially stress corrosion.
B: Mechanical properties.
After cold deformation, the plastic index of aluminium alloy decreases sharply due to the failure of intra-and inter-crystal, lattice distortion and the second type of residual stress, which may approach the state of complete brittleness in the limit state. On the other hand, the strength index of aluminium alloy is greatly improved due to lattice distortion, dislocation increase, grain elongation and refinement, and sub-structure. High, that is, the phenomenon of work hardening.
C: Structure and anisotropy
After large cold deformation, the material exhibits anisotropy due to texture. For example, aluminum alloy sheets are prone to ear-making in deep drawing. Processing conditions should be reasonably controlled to make full use of the advantages of texture and anisotropy, and to avoid or eliminate its disadvantages.
