Reduced residual stress and retained properties in Al-Zn-Mg-Cu alloys using a novel cladding quenching process

The quenching induced residual stresses in Al-Zn-Mg-Cu alloys will severely deteriorate their performances during machining and service processes. In the present work, a novel cladding quenching method, in which a high-temperature inorganic adhesive and aluminum foil were cladded on the surfaces of Al-Zn-Mg-Cu alloys thick plates, was proposed to reduce the quenching residual stresses. The results indicated that the quenching residual stresses were reduced remarkably with increased cladding layer thickness. Meanwhile, the aged alloys maintained superior mechanical properties and exhibited high conductivities after the cladding quenching process with cladding layer thicknesses of 0.4−0.6 mm. Comparing to the aged alloys using conventional quenching, lower dislocation density, similar nano-precipitate characteristics of grain interiors and more discontinuous precipitates at grain boundaries were characterized in the aged alloys using cladding quenching process. The in-depth mechanisms of reduced residual stress and retained properties were discussed also discussed based on further investigations of finite element analysis and time-temperature-property curve.