S. Deepak Kumar

Solid fraction evolution characteristics of semi-solid A356 alloy and in-situ A356-TiB2 composites investigated by differential thermal analysis

The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature relationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 (x = 2.5wt% and 5wt%) composites using differential thermal analysis (DTA). The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2°C and 3°C in liquidus temperatures and a variation of 3°C and 5°C in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction (fs) vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.

Erosion Response of Thixoformed A356-5TiB2 in situ Composite Using Taguchi's Experimental Design

ABSTRACT The present article describes the application of Taguchis experimental design methodology to investigate the erosion wear behavior of in situ-formed A356-5TiB2 composite subjected to thixoforming. The effects of process parameters—such as impact velocity, erodent temperature, erodent size, standoff distance, and impingement angle—on the erosion rate have been analyzed. The results indicated that impact velocity is the most significant factor and accounts for 42.31% of the total effect on the erosion rate of the thixoformed A356-5TiB2 composite. It is found that material loss during erosive wear is primarily due to microploughing (i.e., abrasive type) and microfracture (i.e., impact type). The erosion rate of thixoformed A356-5TiB2 in situ composite was found to be 48.82 mg/kg, which is nearly 44% lower than that of as-cast alloy.

Optimization of process parameters during machining of thixoformed A356-5TiB 2 in-situ composite using Design of Experiments

The current work emphasizes Aluminum based metal matrix composites with TiB2 as reinforcement are emerging materials because of their potential for applications in automotive and aerospace industries. The machining of these materials has become a very important subject for research. This paper presents the application of Design of Experiments and analysis of variance in optimizing the machining process parameters such as cutting speed, feed rate and depth of cut, during turning operation. The response considered for the analysis was surface roughness. The results indicated that A356-5TiB2 composite produces higher tool wear, surface roughness and minimizes the cutting forces. Moreover, there was improvement in the quality of the machined surface in the A356-5TiB2 composite compared to A356 alloy. The chips formed during turning were characterized by Scanning Electron Microscope and analyzed from the machinability point of view. Optimum machining parameters for minimizing the surface roughness were determined. Thus, this work is an attempt to study the machinability behavior of thixoformed A356-5TiB2 in-situ composites.

Production of semi-solid feedstock of A356 alloy and A356-5TiB2 in-situ composite by cooling slope casting

Cooling Slope casting process has gained significant importance for manufacturing of semi-solid feedstock Al alloys and composites which find applications in automotive and aerospace industries. The primary objective of this research is to generate the semi-solid feedstock suitable for thixoforming process. The current work discusses the phenomena involved in the evolution of microstructure of the semi-solid feed stock by Cooling Slope casting process and the effect of various parameters. The process parameters like the angle and length of inclined plate affect the size and morphology of ?-Al phase. The Cooling slope process resulted in the formation of fine grain size of about 38 ?m of ?-Al phase, compared to that of 98 ?m processed conventionally. Further, the pouring temperature played a crucial role in the generation of semi-solid microstructures in case of both the alloy and composites. Moreover, fine TiB2 particles of size 0.2-0.5 ?m are uniformly distributed in the almost spherical ?-Al grains and at the grain boundaries in the composite feed stock. Cooling slope casting route is a suitable and economical route for semi-solid slurry generation by effectively varying the process parameters.