EFFECTS OF PRIOR HEAT TREATMENTS ON THE WELDABILITY AND CORROSION RESISTANCE OF AIRFRAME ALUMINIUM ALLOY

Abstract

The effects of prior heat treatment on weldability and corrosion resistance of Al-Zn-Mg alloys produced by sand casting method were investigated. The cast Al-Zn-Mg alloy samples were heat treated before welding. The samples were divided into six groups viz; as-cast unwelded samples, as-cast welded samples, normalized unwelded samples, normalized welded samples, quenched unwelded samples and quenched welded samples. All these samples were subjected to Tensile and Hardness tests as well as corrosion resistance assessments. The results show that the least Ultimate Tensile Strength of 220 MPa was recorded for as-cast welded alloy while the highest Ultimate Tensile Strength of 350 MPa was recorded for quenched unwelded alloy. The least Hardness of 56.1 Hv was recorded for as-cast welded (FZ) alloy while the highest Hardness of 92.8 Hv was recorded for quenched unwelded samples. Prior heat treatment processes reduced the corrosion resistance in the acidic environment while it improved it in the near-neutral environment making the Al-Zn- Mg alloy more stable in the near-neutral environment. The research work established the fact that prior heat treatment can be utilized to improve the properties of welded Al-Zn-Mg alloy