Effect of the modification structure for Newton's metal on some its properties for industrial applications

Newton's metal is important for industrial applications that is the reason for studying the effect of modified structure of it ’ s on mechanical and thermal properties. Microstructure, mechanical properties such as elastic modulus Vickers hardness, internal friction and melting temperature of Bi 50 Pb 34 Sn 16, Bi 50 Pb 28 Sn 22, Bi 50 Pb 22 Sn 28 and Bi 50 Pb 16 Sn 34 alloys have been studied and analyzed. X-ray analysis of these alloys show that, it contained different phases with formed a solid solution. Elastic modulus variable decrease, melting temperature varied, internal friction and Vickers hardness increased due to modified Newton's metal (Bi 50 Pb 31.2 Sn 18.8 ) alloy.


Introduction
Fusible alloys have low melting points compositions as bismuth, lead, tin, cadmium, or indium, which used in many applications such as fusible element in safety devices [1][2][3] and alarms, radio-opaque contrast medium in x-ray, solder and nuclear medicine as a shielding block [4]. Microstructure, thermal parameters, internal friction, wettability and electrochemical corrosion behavior for bismuth-tin based alloy, Bi30Sn50Sb10Al5Zn3Cu2, Bi25Sn61Sb5Zn4Al3Ag2, and Bi20Sn60Sb7Al5Zn3Cd3Cu2 alloys were studied by different experimental techniques. The results show that, properties for Bi-Sn alloys based changed after adding alloying elements [5,6].
Several studies [7][8][9][10][11][12][13][14][15][16] covered structure, mechanical and thermal properties of bismuth based or tin based alloys with studying the effect of alloying elements on their properties. The aim of this research is to study the effect of modified structure on mechanical and thermal properties of bismuth based alloys.

Materials and methods
Bismuth, tin and lead metals with purity more than 99.9 % were used to prepare Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys. These alloys (mixed metals by weight percentage) are melted and then normal casted on substrate. The samples are prepared in convenient shape for all tests. Microstructure for alloys is performed using Shimadzu X-ray Diffractometer, (Dx-30, Japan) Cu-Ka radiation with l=1.54056 Å at 45 kV and 35 mA and Ni-filter, in the angular range 2q ranging from 0 to 100° in continuous mode with a scan speed 5 deg/min. The differential scanning calorimetry (DSC) thermographs are obtained by Universal V4. 5A TA Instrument with heating rate 10 k/min in the temperature range 0-400 C. Micro-hardness test of used specimens were conducted using a digital Vickers micro-hardness tester, (Model FM-7, Tokyo, Japan), applying a load of 100 gm for 5 seconds via a Vickers diamond pyramid. Ten measurements were recorded for each sample and then the mean value of all measurements was used. The internal friction and dynamic elastic modulus measurements of used samples were carried out with the modified dynamic resonance, which vibrates electro dynamically and is based on a standing-wave phenomenon [17][18][19][20].

Results and discussion
3.1 Microstructure X-ray analysis Figure 1 shows x-ray diffraction patterns of Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys. From x-ray diffraction patterns, Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys have sharp lines of rhombohedral crystals of bismuth, body-centered tetragonal tin, body-centered tetragonal bismuth-tin (agree with the results of [21,22] and hexagonal crystal of Bi3Pb7 inter-metallic compound which is agree with the results show by Kil-Won Moon et al [23]. The x-ray analysis show that, feature for formed phases such as crystallinity (peak intensity), crystal size (peak broadness) and orientations (peak position, 2θ) for Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 changed due to modified structure (increased Sn content with deceased Pb content). That is because these atoms dissolved in matrix alloy formed a solid solution and\or undetected phases

Thermal properties
Thermal analysis depend on the nature of solid phase and on its temperature. It is used to study solid state transformations as well as solid liquid reactions. The DSC thermographs are obtained with heating rate 10 C /min in the temperature range 0-400 C. The melting temperature of Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys is presented in Table 1, which is dependent on its composition. Bi50Pb22Sn28 94

Internal friction
The internal friction is determined from the resonance peak-width technique which is preferred than the other method of free decay curve which suitable for low values of internal friction. The internal friction value Q -1 of Bi based alloys, listed in Table 2, is affected by the alloy composition. That means, it is sensitive to the internal structure (mobile atoms in the matrix which increase or decrease the resonance frequency and the motion time).  Table 3 shows Vickers hardness value for Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys. It is increased by increasing tin content with decreasing lead content that means the hard inclusions in the matrix surface increased.

Elastic modulus
Elastic modulus value for Bi50Pb34Sn16, Bi50Pb28Sn22, Bi50Pb22Sn28 and Bi50Pb16Sn34 alloys decreased by increasing Sn content and decreasing Pb content as listed in Table 4. It is increased by increasing tin content with decreasing lead content that means the hard inclusions in the matrix surface increased.

Conclusion
In this work lead content in used alloys decreased by 53%, that's mean the toxicity decreased, healthy environmental, for industrial applications. Internal friction and Vickers hardness increased but elastic modulus decreased for bismuth based alloys at tin increase with lead decrease.