Date

2017

Document Type

Thesis

Degree

Master of Science

Department

Materials Science and Engineering

First Adviser

Wojciech Z. Misiolek

Abstract

Hot forgoing processes are used for plastic deformation of metals at temperatures above the material recrystallization temperature. In this process metal ingots are converted into complex shapes by applying stresses above the yield stress of the deformed material on pre-heated metals in a short period of time. Hot forging process provides products with high strength due to grains refinement and absence of porosity. In the recent years, the demand of aluminum forged products has increased comparing with the cast products, largely in the automotive industry. Many materials characteristics such as: good mechanical properties, low weight, good corrosion resistance, low forging pressure and an ability to be forged into complex shapes make forged aluminum alloys favorable in automotive industry. [1] Because of that, a good understanding of the hot deformation behavior and microstructural evolution are important in a design of the optimized hot forging processes. The objective of this research is to determine the flow stress behavior and microstructure evolution of newly developed aluminum alloy AA 6099 used in the closed die forging process for truck automotive wheels. As a part of physical process simulation Gleeble hot compression tests were performed at strain rates of 0.01, 0.1 and 1 s-1 and temperatures of 350, 400, 450 and 500 ˚C up to a strain of 0.8. The flow stress value is dependent on the deformation temperature, strain, and strain rate and the test parameters were selected in such a way to simulate industrial conditions. The flow stress decreases with increasing deformation temperature and/or decreasing the strain rate. Light Optical Microscopy (LOM), Electron Backscatter Diffraction (EBSD) and microhardness investigations were performed on the hot deformed samples. They revealed that material softening is a result of dynamic recovery and/or partial dynamic recrystallization at temperature of 350 ºC. Also, after solution heat treatment of the hot deformed samples, there was some evidence of static recrystallization and grain growth.

Included in

Metallurgy Commons

Share

COinS