Date

2016

Document Type

Thesis

Degree

Master of Science

Department

Mechanical Engineering

First Adviser

Misiolek, Wojciech

Abstract

Continuous Rotary Extrusion (CRE) is well known process known also under Conform name used for extrusion of Aluminum and Copper alloys. Magnesium is the lightest major engineering construction metal, and due to its good mechanical properties, it has been used increasingly as a substitute for aluminum and steel in particularly aerospace and automotive industries. Magnesium alloys are difficult to deform at room temperature due to its hexagonal crystal structure. Therefore, Magnesium has to be processed at elevated temperature in order to take advantage of the increased ductility at these temperatures. From the literature survey it is clear that better mechanical properties of Magnesium alloys can be achieved by both hot deformation and dynamic recrystallization and CRE could improve Magnesium alloys properties as it is capable of refining and improve the grain structure. In this work an investigation has been carried out to study the mechanics of the CRE process when used for Magnesium alloys AZ91, by means of FEM- modelling. Using FEM-modelling of the CRE process, mapping of the nature of metal flow by means of temperature, strain and strain rate distribution in deformed material was performed. This allowed different process parameters that are required for the process quality to be analyzed. Four different numerical models of Continuous Rotary Extrusion for Magnesium AZ91 alloy were developed using DEFORM-3DTM software and the influence of different process parameters on the extrudate quality was studied. Through the numerical analysis investigation of the influence of the effective stress, strain, temperature, strain rate and velocity in the CRE process on outcome of four different models was studied. The material behavior under different processing condition has been compared. Process condition which causes plugging and other defects are discussed. The work has been successful as the FEM- model was able to represent the mechanics of the Magnesium alloy processed by the CRE process.

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