The Selection Refiner Of Pure Mickel And On The Refinement Mechanism

According to Hall-petch formula, grain refinement can enhance the strength of materials and plastic materials,so it is to improve the material properties of the effective means. Grain refinement of the method is divided into two major categories of physics and chemistry, in which there is a common method of deformation processing refinement method, the physical field refinement method, the rapid cooling method, mechanical physical method, and add refining refiner and modifier. Approach to physical refining of high purity materials, will not be brought about by external melt inclusions, better refinement; refining effect of chemical additives law stability, the role of fast, convenient operation, strong adaptability, is the most common refinement method.Aluminum and aluminum alloy, magnesium and magnesium alloy by chemical additive method of grain refinement has been reported in the literature, but for refined nickel and nickel alloys are rarely reported in the literature. In this paper, the chemical additive method of grain refinement of pure nickel, pure nickel melt to add a variety of alloying elements and compounds, different alloying elements and compounds on the grain refinement of pure nickel in different capacities, refining capacity of the weak by the strong order of titanium compounds 2, titanium compounds1, pure Ce, rare earth mixed and alloy containing titanium compounds alloy 2.Add alloy containing titanium compounds alloy 2 with the added effect of titanium compounds2 compared to the refined, titanium compounds 2 significantly greater than the effect of the refinement alloy containing titanium compounds alloy 2 of the results, the inferred initial alloy containing titanium compounds alloy 2 which contains the alloying elements for refinement of pure nickel has no effect. Rare Earth Elements in the process of solidification of pure nickel, easy-necking caused by the phenomenon of segregation, so that dendrite fuse, free, an increase of partitanium compounds1le nucleation; rare earth elements at the same time reduce the surface energy, and promote the nucleation due to grain refinement. However, component cooling effect caused by grain refinement usually weak, the grain refinement of pure nickel is less.The results show that titanium compounds 2 additive amount with the increase of grain size of pure nickel decreases, When no added titanium compounds2 grain size for pure nickel 242μm; when titanium compounds 2 additive amount of its adding 0.8%, the grain size decreases to 46μm, further increasing the mass fraction of titanium compounds 2 addition, the grain size remained stable, when the titanium compounds2 additive amount to 1.2%, refinement effect reachs best.Refinement through electron microprobe analysis of the internal sample and found that when titanium compounds 2 additive amount lower, titanium compounds 2 in the nickel melt evenly distributed in the grain and grain boundaries, titanium compounds 2 has played a central role; When titanium compounds 2 additive amounthigher, titanium compounds 2 partitanium compounds1le aggregation, titanium compounds 2 content obvious crystal boundary is higher than the Internal grain, titanium compounds 2 grain boundary migration slow down the speed of the grain boundary to grain size heterogeneity.The use of contact angle theory, the theoretical lattice constant of a considerable, non-homogeneous nucleation in the rationale for electrostatic theory, qualitative analysis of the titanium compounds 2 refinement mechanism of pure nickel. Titanium compounds 2 as a result of an extremely high melting point, high chemical stability, high hardness and excellent electrical properties, from a different theoretical point of view, titanium compounds 2 can be used as an effective nucleation agent, to promote grain refinement of pure nickel.