Ultrafine grained materials through mechanical processing: An assessment

In this paper severe plastic deformation (SPD) and friction stir processing/ welding are examined. The structural changes due to SPD are reflected in improved mechanical properties. Advantages of SPD are pointed out. Within the SPD technique, a number of approaches are possible, e.g., equi-channel angular pressing/extrusion, high pressure torsion, accumulative roll bonding/fold - roll process, reciprocating extrusion – compression, cyclic close die forging, repetitive corrugation and straightening. Analyses available are elementary and often assume uniform stress and strain distribution. These processes are easily adapted to suit standard metal working equipment fitted with inexpensive devices and tools. However, scaling up the processes to handle large billets and achieve large tonnage production is difficult. In the near future, medium and small-scale industrial production only is likely. Friction stir process, a solid state technique for joining similar or dissimilar materials of equal or different thickness, has some key metallurgical, environmental and energy benefits. It is already being considered for applications in aerospace and automotive industries. Significant improvements in surface properties and superplastic flow have been established in friction stir processed materials. Velocity of tool movement and power input needed for fast rotation of the tool are the major variables. Since significant temperature rise is there during processing, in a proper analysis, the boundary conditions arising from thermal and mechanical constraints have to be satisfied simultaneously, which is an extremely difficult. A few key issues have to be addressed before large-scale production can be attempted. An integral approach that takes into account the total system of material, design, mechanics and component forming is likely to lead to industrially relevant solutions

Ultrafine grained materials through mechanical processing: an assessment

In this paper severe plastic deformation (SPD) and friction stir processing/ welding are examined. The structural changes due to SPD are reflected in improved mechanical properties. Advantages of SPD are pointed out. Within the SPD technique, a number of approaches are possible, e.g., equi-channel angular pressing/extrusion, high pressure torsion, accumulative roll bonding/fold - roll process, reciprocating extrusion - compression, cyclic close die forging, repetitive corrugation and straightening. Analyses available are elementary and often assume uniform stress and strain distribution. These processes are easily adapted to suit standard metal working equipment fitted with inexpensive devices and tools. However, scaling up the processes to handle large billets and achieve large tonnage production is difficult. In the near future, medium and small-scale industrial production only is likely. Friction stir process, a solid state technique for joining similar or dissimilar materials of equal or different thickness, has some key metallurgical, environmental and energy benefits. It is already being considered for applications in aerospace and automotive industries. Significant improvements in surface properties and superplastic flow have been established in friction stir processed materials. Velocity of tool movement and power input needed for fast rotation of the tool are the major variables. Since significant temperature rise is there during processing, in a proper analysis, the boundary conditions arising from thermal and mechanical constraints have to be satisfied simultaneously, which is an extremely difficult. A few key issues have to be addressed before large-scale production can be attempted. An integral approach that takes into account the total system of material, design, mechanics and component forming is likely to lead to industrially relevant solutions

Comparative evaluation on the performance of nanostructured TiAlN, AlCrN, TiAlN/AlCrN coated and uncoated carbide cutting tool on turning En24 alloy steel

45-59<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">In the present work, the performances of the nanostructured TiAlN, AlCrN, TiAlN/AlCrN coated are evaluated by comparing the machining performance with uncoated carbide cutting tool by conducting the machining studies on En24 alloy steel. Taguchi’s experimental design is used to design the turning experiments and fix the turning parameters, such as the cutting speed (<i style="mso-bidi-font-style: normal">V), feed rate (f) and depth of cut (d). The signal-to-noise ratio and anova were used to investigate the effects of the machining parameters and their contribution to the tool wear and surface roughness. The results show that the nanostructured TiAlN/AlCrN coated insert has developed minimum flank wear and shown minimum surface roughness on the machined surface, compared to the TiAlN, AlCrN coated and uncoated tools. The cutting parameters in which the TiAlN, TiAlN/AlCrN coated and uncoated inserts have shown lesser tool flank wear and better surface finish of the work-piece are identified. For the TiAlN tool, the better machining parameters are, cutting speed = 160 m/min, feed rate = 0.119 mm/rev, and the depth of cut = 1.0 mm. For TiAlN/AlCrN, the better machining parameters are, cutting speed = 160 m/min, feed rate = 0.318 mm/rev, and the depth of cut = 0.3 mm, and for the uncoated tool, the cutting speed = 100 m/min, feed rate = 0.318 mm/rev, and the depth of cut = 1.0 mm is the best machining condition. But for the AlCrN tool the minimum tool wear was obtained, when the cutting speed = 40 m/min, feed rate = 0.477 mm/rev, and the depth of cut = 1.0mm and better surface finish of the work-piece was obtained, when the cutting speed = 160 m/min, feed rate = 0.119 mm/rev, and the depth of cut = 1.0 mm.</span