Research On Producing Nanostructured Materials By Machining Al6061 With Large Strain

Severe plastic deformation is one of the most important methods to produce nanomaterial of metals and alloys, and machining with large strain is one of the severe plastic deformation methods which developed in recent years. As more and more scholars and experts get into the research, more people pay attention to the important advantage: the process is simple, low cost, high production efficiency, wide range of use (from the plastic materials to the high hardness material) and so on. In this paper, we combine the finite element simulation and experimental method to study the strain, temperature, microstructure, temperature stability of the chip which related to the machining of large strain. The main results are as follows:(1) The finite element simulation was used to simulate the process of machining with large strain, the temperature and strain which is important to the microstructure of the chip was study. The result shows, in the process of machining, larger strain can get if use larger negative rake, the result is the grains are finer. The change of shear strain is mainly concentrate on the shear region of the narrow scope, that i疤?he first deformation region. In addi??, the most important parameter impact the temperature is cutting speed. When the cutting speed is slow, the temperature increases slowly, so the cutting speed can raised appropriately before the temperature under the dynamic recrystallization temperature.(2) The A16061 was cut with two-dimensional orthogonal in certain cutting and tool parameters, and the microstructure of chip was analysised. The result shows, when the rake is less than 0°, that is the shear strain of A16061 reaches 2.12, the wide-angle grain boundaries of ultra-fine grain can be got., the average grain size is less than 100nm, so it achieves a great deal of grain refinement.(3) After machining, the Vickers hardness was measured, it shows the hardness of nano-chip have improved greatly. The hardness improvement is mainly determined by the increase of dislocation and the grain refinement.(4) The study of temperature stability of chip after machining shows that, the temperature stability is difference corresponded to the different states of A16061. The temperature stability of peak-aged and over-aged A16061 is poor than solution-treated A16061, and the greater the strain, the temperature stability of the materials will be worse.