"Solid method", "gas method" and "electrochemical method". The preparation process of "liquid method" mainly includes arc melting, vacuum induction melting, laser cladding, etc. "Solid method" is mainly mechanical alloying method, "gaseous method" is mainly ion sputtering deposition, and "electrochemical method" is mainly electrochemical deposition. Among them, arc smelting is the most commonly used method in the preparation of high entropy alloys. It is an electrothermal metallurgy method which uses electric energy to generate an arc between the electrode and the melted material to melt the metal. The content of gas and volatile impurities of the metal melted by electric arc furnace decreases, and the ingot will not appear loose center generally, and the crystallization is more uniform. However, there are some problems in this method, such as electrode pollution, poor arc stability, slow melting speed, low efficiency, difficult to control the proportion of alloy composition, and easy to produce composition segregation. In order to make the composition uniform, it is often necessary to melt repeatedly, the process is more complicated, and the power consumption is large. NbMoTaW high entropy alloy and preparation method thereof.
NbMoTaW high entropy alloy and preparation method thereof. The forming method is a combination of mechanical alloying and discharge plasma sintering. This invention method makes high melting point of niobium, molybdenum, tantalum, tungsten, four kinds of metal in the solid state implementation alloying, don't need to be heated to melting point temperature, only a solid phase sintering (sintering temperature not over 1600 ℃) can get better performance of bulk materials, overcome the smelting method the problem of high melting temperature (> 2900 ℃), the processing temperature reductions and process is simplified. The microstructure of NbMoTaW high entropy alloy of the invention is a granular second phase dispersed in an equiaxed crystal matrix, both the matrix phase and the second phase are BCC solid solutions, and the average grain size of the matrix is <6μm. However, the average grain size of the second phase is less than 4μm, the material has fine grains, uniform structure, no dendrite segregation, and has high strength and hardness.
High entropy alloy is a new type of alloy developed in recent years. Different from the traditional alloys with one or two elements as the main elements, the high-entropy alloys contain multiple main elements, which are generally defined as the alloys with five or more elements alloyed according to the equal atomic ratio or close to the equal atomic ratio. The generalized high-entropy alloys also often include the alloys with four or three principal elements. Because of the high mixing entropy of these alloys, they tend to form single-phase or multiphase simple high-entropy solid solutions rather than complex structures such as intermetallic compounds. The existing research results show that high-entropy alloys have some properties better than traditional alloys, such as high strength, high hardness, resistance to tempering and softening, high wear resistance, good corrosion resistance and special magnetic properties. It is a new frontier research field after amorphous alloys in materials science.
