12-04-2012, 02:58 PM
Effects of process parameters on warm and electromagnetic hybrid
forming of magnesium alloy sheets
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Introduction
Weight reduction is a primary concern in the automotive and
electrical industries due to the intense requirements of energy conservation
and emission reduction. General efforts have been made
to decrease the weight of automobile constructions by increasing
the use of lightweight materials. As the lightest structural
metal, magnesium (Mg) alloy has attracted increasing interest from
both the industrial and academic fields. Friedrich and Schumann
(2001) reported thatMgalloys used for automobile parts are mainly
processed by die casting. Die casting technology allows the manufacture
of parts with complex geometries. However, Doege and
Droder (2001) introduced the idea that the mechanical properties
of these parts often do not meet the requirements concerning
endurance strength and ductility, among others.
Experiments
2.1. Experiment materials
The materials used in this experiment included commercial
Mg-based alloy AZ31 sheets 1.0mm in thickness obtained by
the tandem rolling method. The sheets were annealed for 1 h
at 300 ◦C. To investigate the effects of the process parameters
on the bulging height, 90mm×90mm specimens were used. To
analyze the forming limit of AZ31 sheets under different conditions,
90mm×90mm, 90mm×70mm, 90mm×50mm, and
90mm×30mmspecimens were used. A grid pattern of circles was
marked on the surfaces of the sheets prior to forming. The chemical
composition of the AZ31 alloy sheets are listed in Table 1.
Results and discussion
3.1. Effects of discharging energy
Different bulging parts were formed from the sheets by altering
the discharging voltage, capacitance, and forming temperature.
When the discharging voltage was too high, however, the workpieces
were ruptured.
Fig. 5 shows the dependence of the bulging height of the AZ31
sheets on the discharging voltages at different temperatures (all
workpieces were formed at a capacitance of 550F). Figs. 6 and 7
show the dependence of the bulging height of the AZ31 sheets
on the capacitance and discharging energy at room temperature,
respectively
Conclusions and outlook
In this paper, a process of warm and electromagnetic hybrid formation
of Mg alloy sheets was successfully established. The effects
of the process parameters on the forming efficiency and formability
of Mg alloy sheets were investigated by bulging experiments.