Residual stresses in the aluminium alloy 2014A subject to PAG quenching and vibratory stress relief

Abstract

Generic hollow pump bodies made from aluminium alloy 2014A forgings have been solution heat treated and quenched into either cold water or polyalkylene glycol (PAG) solutions. An industry standard PAG type synthetic quenchant was evaluated, and the influence of two concentrations of the PAG solution on residual stress in the pump bodies was characterised, using neutron and X-ray diffraction. These residual stresses were then compared to those resulting after a pump in the as quenched condition was subject to a widely known but controversial commercial vibratory stress relieving procedure. The use of neutron diffraction allowed the through thickness residual stresses to be evaluated in the pumps. Results demonstrate that PAG quenching is highly effective at significantly reducing residual stress when compared to cold water quenching, but the impact is non uniform and cannot be simply quantified. In this investigation, we prove the effect of vibratory stress relief is negligible, and much less than that achieved by PAG quenching.