Preparation And Investigation On Microstructures Of Silicon Monel Alloy

Monel alloys with different Si contents were prepared by vacuum melting utilizing different melting technologies, the characteristics of the microstructure of the silicon monel alloy as well as the effect of processing parameters and silicon addition the microstructure and properties of silicon monel alloy were studied. The following conclusions can be drawn from those investigations:1. The as-cast microstructures of the silicon monel alloy consists of dendritic a matrix, net-shapedα+βeutectic phase distributed in the interdendrite and precipitated secondaryβphase.2. As melting temperature increases from 1350℃to 1450℃with a step of 50℃, the dendrite of silicon monel alloy becomes finer, the amount of eutecticβphase decreases and secondaryβincreases. At 1450℃, the alloy has the finest dendrites, the least amount of eutecticβphase and the most amount of secondaryβphase.With further increasing to 1500℃, there is no obvious change of the microstructue compared with that prepared at 1450℃.With increasing melting temperature, the hardness of silicon monel alloy increases. The distribution of measured hardness is narrower, and macrosegregation of the alloy is alleviated. The maximum hardness can reach HB372 at the 1450℃. When the temperature is 1500℃, there is no obvious change of the hardness compared with that prepared at 1450℃.3. When the silicon monel alloy was melted at 1450℃holding for 30mins, 60mins, 90mins and 120mins respectively, the dendrite as well as the amount of eutecticβphase of silicon monel alloy decrease and then increase. On the contrary, the amount of secondaryβphase increases and then decreases. The alloy has the finest dendrites, the least amount of eutecticβphase and the largest amount of secondaryβphase at 60 mins.With increasing holding time, the hardness of silicon monel alloy increases and then decreases, and the degree of macrosegregation alleviates and then aggravates. At the holding time of 60mins, the maxium hardness of the alloy can reach HB372, the measured hardness is more closer to the average value with smaller deviation and the degree of macrosegregation is the least.4. With increasing the silicon additive in the range of 3.0-4.5wt%, the dendrite of silicon monel alloy becomes finer, the amount of eutecticβphase decreases and secondaryβincreases. When the silicon content is 4.5wt%, the alloy has the finest dendrites, the least amount of eutecticβphase and the most amount of secondaryβphase. With increasing silicon content, the hardness of silicon monel alloy increases. When the silicon content is 4.5wt%, the maxium hardness of the alloy can reach up to HB372, the measured hardness is more close to the average value with smaller deviation and the degree of macrosegregation is the least.