project_ppt
- 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
- 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