Title

Effect of welding on the width of the heat-affected zone of aluminum alloys.

Date of Award

2004

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

Keywords

Engineering, Civil.

Rights

CC BY-NC-ND 4.0

Abstract

Present aluminum design standards and specifications in North America require that the zone affected by welding be taken to extend a distance of 25 mm each side from the centre of the weld and that the yield strength of the metal in the zone affected by the weld be taken as the welded yield strength. The objective of this investigation is to determine the effect of welding on the width of the heat-affected zone (HAZ) of aluminum alloys. This was required for the development of an equation to determine the width of the HAZ for different parameters. One hundred and thirty-nine weldment specimens were fabricated using five alloys, seven material thicknesses and different heat inputs. The hardness was measured in the HAZ to determine the width and hardness gradient. The investigation has determined that the width of the HAZ depends on several parameters. The heat input has the most influence on the width of the HAZ. Minimizing the heat input with the use of an automatic process mode is very beneficial. Factors such as thickness, thermal conductivity, heat treatable and non-heat treatable alloys, multi-pass welding and heat-sink compounds also have an effect on the width of the HAZ. The application of a heat-sink compound provides a reduced width of the HAZ. Based on this experimental and theoretical investigation it is concluded that welded connections with properly selected weldable aluminum alloys and material thickness, using an automatic process mode, with a low and uniform heat input and with the use of a properly designed welding procedure, can have the width of the HAZ substantially reduced. Twenty-five cantilevered structures were tested to confirm the adequacy of the specimen testing. FEA using ADINA-T was carried out to develop an empirical-analytical equation for the determination of the width of the HAZ for different aluminum alloys. Current design standards and specifications, which use a constant width of the HAZ and the minimum welded yield strength across the HAZ, should be modified by incorporating the developed equation of this research having variable factors depending on the variable parameters, thus providing a uniform safety margin.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .A44. Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 1044. Thesis (Ph.D.)--University of Windsor (Canada), 2004.