1. The document presents research on the effect of mechanical vibrations on grain refinement during solidification of AZ91 magnesium alloy. 2. Experiments involved vibrationally casting AZ91 alloy at frequencies from 15-35 Hz and analyzing microstructure, hardness, and wear resistance. 3. Results showed that vibrating at 15 Hz produced the finest grain structure and best mechanical properties compared to untreated alloy, with increased hardness and wear resistance.

1. Submitted By:-
Anmol Rathi
Palash Jain
Abhinav Purohit
Yogesh Singh Tanwar
Abhishek Ramawat
Pramod Yadav
Effect of Mechanical Vibrations on Grain
Refinement during Solidification of AZ91 Mg
Alloy
MALAVIYA NATIONAL INSTITUTE
OF TECHNOLOGY
Guided By:-
Prof. Upender Pandel
Metallurgical & Materials Engineering Department

2.  In the last few years, a great range of magnesium alloys have been
developed, emphasizing the increasing demand of the
transportation and electronic industries for advanced structural
materials with enhanced properties.
 The requirements become even more scrupulous when new
magnesium alloys are developed to address specific and critical
applications.
 One of the most imperative benefits of magnesium based alloys is
their specific strength (strength to base ratio).
 More than ever the magnesium alloys are used in notebook PC’s,
MD players, pocket telephones and digital cameras to accomplish
lighter and thinner parts.
Introduction

3. Magnesium alloy components are usually produced by casting
processes. The most commonly used commercial materials in
automotive fields are Mg- Al based alloys, such as AZ and AM
series magnesium alloys. Manganese is a valuable element in
these alloys that lessen the influence of harmful iron. Generally,
manganese is normally 0.1 to 0.35 mass % to enhance corrosion
resistance.

4.  Low Density
 High Specific Strength
 Good Castability
 Good Damping Capacity
 Easy Machinability
Advantages of Magnesium Alloys

5.  Highly Anodic
 Poor High temperature properties
 Limited cold workability and toughness.
Limitations of Magnesium Alloys

6. Applications

7.  The solidification behavior of magnesium alloys is affected by
alloying elements, grain refiners and cooling rate during
solidification. The growth morphologies of both the primary
dendrites and the eutectic are highly dependent on the
aluminum content and cooling rate.
 All the commercial magnesium alloys start forming magnesium
solid solution at the early stage of solidification which is denoted
as α- Mg. the nucleation of the primary phase is sometimes
controlled by the addition of grain refiners.
Solidification of Magnesium Alloys

8.  Most commercial magnesium products are produced by HPDC,
which has a very high cooling rate and resulted in a high driving
force for nucleation. This causes increased nucleation and
therefore creates a large number of primary grains thus reduces
the need for an effective grain refiner.
 For most commercial Mg- Al Alloys, it is common to observe
eutectic constituents even the Al content is as low as 2 wt%.

9.  The grain size available by conventional casting process is large
resulting in poor mechanical properties of the product
 Although grain refinement of magnesium can be achieved by the
wrought process in which bimodal structure consisting of both
coarse grains and fine grains is present. In some coarse grains,
deformation twins are easily formed and result in a limited
ductility at the crack initiation sites
 To suppress the formation of coarse dendrites is a key issue in
improving the alloy properties
 Therefore, an improvement of this structure is necessary to
enhance the mechanical properties
Problems with Current Casting Processes

10.  External additives into α-Mg alloy may be of detriment to the
recyclability of the alloy
 Alternative approaches to grain-refining is to use physical fields
such as pulsed electric current, magnetic fields and ultrasonic
vibration during the solidification process of Mg alloys to refine
the grain size
 Meanwhile, because of a simple system, mechanical vibration
attracts attention

11. Vibrations
 Vibration is concerned with the oscillatory motion of physical
systems, the motion may be harmonic, periodic, or a general
motion in which the amplitude varies with time.
 For example, vibration of turbine blades, chatter vibration of
machine tools, electrical oscillations, sound waves, vibrations of
engines, torsional vibration of crankshafts and vibration of
automobiles.

12.  In this method, the entire mold is set into vibrations by means of
a vibration source. Although the use of a mechanical vibrations
allows limited degrees of freedom to the operator, it is the most
promising method of applying vibrations to solidifying melts
due to its simplicity and the ruggedness of the equipment
needed for introducing vibrations. To induce mechanical
vibrations in a permanent mold an electromagnetic shaker can
be used. It was founded that the degree of fragmentation
increases with the amplitude of vibration.
Mechanical Vibrations

13. Metal as casting Metal cutting and
re-melting
Vibrational casting
Sample preparation
Testing
Experimental Procedure

14. Experimental Equipments
 Master alloy was prepared using muffle furnace
 Metal cutting was done using circular band saw machine
 Re-melting of alloy was done in bottom pouring furnace
 Vibrational casting was carried out using mechanical vibrator
placed under bottom pouring furnace
 Test samples were prepared using circular band saw machine

15. Experimental Parameters
Mould Design and Dimensions

16. Flux Composition

17. Casting Parameters
S.No.
Frequency
(Hz)
Amplitude
(mm)
Pouring
Temperature
(oC)
1. 15 2.5 700-740
2. 20 2.5 700-740
3. 25 2.5 700-740
4. 30 2.5 700-740
5. 35 2.5 700-740

18. Testing
Optical
Microscopy
XRD
Wear Testing

19. Results
ELEMENTS Cu Mn Zn Oxygen Al Mg
% 0.019 0.124 2.27 7.07 7.8 85.84
Compositional Analysis:

20. Micrographs:
As Cast 15 Hz
 Samples for Micrograph Analysis were taken at 25 mm from the
bottom of casting
 Micrographs were captured at 50X magnification

21. 20 Hz 25 Hz
30 Hz 35 Hz

22. X-Ray Diffraction Analysis:
As Cast

23. 15 Hz
20 Hz

24. Wear Test Analysis:
AZ91 Alloy
Weight Loss (gm)
5 N 10 N
As Cast 0.012 0.029
15 Hz 0.004 0.022
20Hz 0.007 0.024
25 Hz 0.0121 0.025
30 Hz 0.012 0.028
35 Hz 0.013 0.084
 Amount of material loss at 5 N and 10 N in 1500 seconds was
observed

25. Conclusion
 Vibrational solidification causes refinement of the grain in the
Magnesium alloy
 By applying vibrations to the melt, a uniform distribution of
the fine grains of the primary α-Mg phase is achieved, and a
dense network like eutectic β-phase solidified
 The refinement of the grains by vibrations results in an
increased wear resistance of magnesium alloy
 It is noticeable that through Vibrational solidification at the
frequency of 15 Hz of AZ91 Mg alloy, most grain refinement is
taking place and the material have better mechanical and
metallurgical properties then the As Cast alloys
 Vibrational solidified Magnesium alloys can be used more
effectively as alternative to current materials