Thermal relaxation of residual stress in shot-peened CNT/Al–Mg–Si alloy composites

Abstract

Abstract A carbon nanotubes (CNTs)-reinforced Al–Mg–Si alloy composite was made and shot peened. After shot peening, a compressive residual stress field was generated in shot peened layer. The change law of residual stress and microhardness with annealing time at elevated temperatures (150\xa0°C, 200\xa0°C, and 250\xa0°C) was investigated. An Al–Mg–Si alloy without CNT addition is prepared in the same process to compare with the CNTs/Al–Mg–Si alloy composite to verify the effect of CNTs on residual stress relaxation. Results showed that for the both materials, macro and micro residual stresses in the shot-peened layers decreased firstly due to thermal recovery and then trend to be stable during annealing process. Increasing the annealing temperature could accelerate the speed of stress release and increase the decrement rate. Specially, the addition of CNTs could improve the thermal stability of the macro residual stress created by shot peening.