12.2.2 Laser Cutting Process and Cutting Parameters All of the laser cutting processes have been carried out on a CO2 laser machine called “4000-TLF TURBO” Basic parameters of laser cutting process have been given in the Table 12.2. In the present work, three levels of powers (Pw) and three levels of cutting speeds (S), with three different gas pressures (Gp) have been chosen in order to examine their impact on the basic performance parameters. Nine samples were cut for each composition. Totally, 27 Laser-cutsamples were used and these samples have been prepared for damage evaluation (Fig. 12.1). After achievement of the cutting process, the widths of resulting cuts were measured and SEM micro-photography of the cutting surfaces was carried out. To measure the striation depths and widths, the surface roughness measurement was carried out using a 3D optical roughness meter (Surf-Scan). For intensive evaluation, measurements were taken in different zones for each composition (Remelted Zone, Heat Affected Zone (HAZ) and the centre of the specimen) by using SEM. Optimization process for the experimental matrix with variables was employed to develop for each experimental test. Taguchi method and L9 Orthogonal Array were used to reduce number of the experiments. The design of experiments (DOE) and measurements of the average roughness values “Ra” have been carried out with Minitab 17 software. All of the optimization parameters were evaluated for each composition with these diagrams obtained by software. 12.3 Results and Discussions 12.3.1 Microstructure of (TiN +Al2O3) Reinforced Aluminium Matrix Composites It is well known that the structures of the ceramic particulates reinforcement aluminum matrix composites are complex hybrid characters. Distribution of TiN in the matrix is relatively difficult regarding to other ceramics (i.e. Al2O3, TiB2, etc.) due to low wettability (Fig. 12.2). In this work, TiN particulates (size of particles is variable between 3 and 20 μm) were treated before mixing with matrix to activate surface of powder and a little amount of BN was added to improve its cohesion with matrix. The presence of the intermetallic phases is confirmed and estimated that solid state phase reactions start during the treatment of mechanofusion. Additionally, Al2Cu was also observed after a heat treatment at 750 K during sintering process. Table 12.2 Basic parameters of CO2 laser cutting process Cutting parameters Levels Min Medium Max Power (W) 3000 3500 4000 Cutting speed (m/min) 0.048 0.144 0.192 Gas pressure (nitrogen) (bar) 4 8 14 Fig. 12.1 Experimental specimens cut using CO2 laser cutting process 12 Laser Cutting of the TiN +Al2O3 Reinforced Aluminium Matrix Composites Through Semisolid Sintering 117
RkJQdWJsaXNoZXIy MTMzNzEzMQ==