W.F. Zhou

Initial dislocation density effect on strain hardening in FCC aluminium alloy under laser shock peening

Abstract The effect of initial dislocation density on subsequent dislocation evolution and strain hardening in FCC aluminium alloy under laser shock peening (LSP) was investigated by using three-dimension discrete dislocation dynamics (DD) simulation. Initial dislocations were randomly generated and distributed on slip planes for three different dislocation densities of 4.21 × 1012, 8.12 × 1012 and 1.26 × 1013 m−2. Besides, variable densities of prismatic loops were introduced into the DD cells as nanoprecipitates to study the dislocation pinning effect. The flow stresses as a function of strain rate obtained by DD simulation are compared with relevant experimental data. The results show a significant dislocation density accumulation in the form of dislocation band-like structures under LSP. The overall yield strength in FCC aluminium alloy decreases with increasing initial dislocation density and forest dislocation strengthening becomes negligible under laser induced ultra-high strain rate deformation. In addition, yield strength is enhanced by increasing the nanoprecipitate density due to dislocation pinning effect.

High temperature wear performance of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy subjected to laser shock peening

ABSTRACT This paper investigates the influence of laser shock peening (LSP) parameters on surface integrities and high temperature wear performances of Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloy. Surface integrities include surface roughness, residual stress and micro-hardness are measured. High temperature wear performance of TC11 alloy with and without LSP are investigated. The results indicate that multiple LSP impacts can improve surface micro-hardness and induce compressive residual stress in the surface layer. Moreover, the friction coefficient and wear rate of TC11 alloy significantly decrease after LSP with optimised parameters. The improved wear performance is ascribed to the low surface roughness, higher surface micro-hardness and compressive residual stress induced by multiple LSP impacts in the surface layer.