Comparative Study of Microstructure Evaluation and Mechanical Properties of Titanium Alloy Grade 5 Composite Via Laser Metal Deposition

Abstract

Abstract The implementation of A.M processes in manufacturing is sustainable since it provides higher efficiencies, accuracy and minimal material waste compared to conventional manufacturing methodologies. The investigation of this research was carried on Titanium alloy base metal with Ti-Al-Si-Cu reinforcements. The deposition process was conducted employing a 3kW (CW) Ytterbium Laser System (YLS-2000-TR) machine, coaxial to the reinforcement powder. The laser scanning speed and power were varied between the intervals of 1-1.2 m/min and 900-1000 W. All other parameters kept constant where the rate of gas flow, the spot diameter, and the rate of powder flow. The mechanical property such as ultimate tensile strength was determined for all specimens conducted. The microhardness values were obtained by performing Vickers hardness tests on the metallurgical prepared surfaces. All the samples were observed under an Optical Microscope (OM) to perform microstructural analysis. Optical microscopy and Scanning Electron Microscopy (SEM) were used to determine the metallurgical evolution in the fabricated specimens and the geometrical properties. It was observed that all the samples produced by the LMD technique showed several layering of prior β grains that grew in the direction parallel to the deposition direction. This was caused by the layers being repetitively melted. Specimens produced with densities of energy deposition in regions of a complete fusion and melting resulted in the roughness of the surface and hardness being uniform. Varying the scan speed and laser power supported the generation of columnar grains. The columnar structures are compact and are small in width attributing to the dominance of the diameter of the laser and space of the hatching on the grain size of the columnar structures. Micro-hardness analysis showed that the average hardness of the Ti-6Al-4V substrate was approximately 358HV and the improved hardness was 528HV which was found within the coating at a laser scan speed of 1.2 m/min and laser power of 900 W. It is evident that all the specimens had increased microhardness, in comparison to the parent material, other than samples 4B. Sample 5B displayed the most increase in microhardness of 32.20%, which is the sample with the highest microhardness of 528 HV.