Heat treatment of 319.2 aluminium automotive alloy Part 2, Ageing behaviour

In this part of a two-part study of the heat treatment of 319.2 aluminium alloy, the hardening behaviour upon artificial ageing in the temperature range 155‐220 °C for periods of up to 24 h has been investigated. The test bars used were solution heat treated for 8 h at 515 °C (see Part 1). The results show that peak-ageing is achieved after 24 h at 155 °C or 5 h at 180 °C, giving 253 MPa yield strength, 403 MPa ultimate tensile strength, and 1.2% elongation. Inclusions and oxides have a marginal effect on the yield strength; however, they deteriorate both the ultimate tensile strength and % elongation to levels below those obtained in the as-cast condition. Quality index against ageing time relationships have been discussed in terms of the ageing conditions.