| In this peper，a Ni-base single crystal superalloy DD22was employed to study the effectof Ru addition(0wt.%,3wt.%,5wt.%) on the solidification behavior, microstructural evolutionand mechanics property of single crystal superalloys by using scanning electron microscope(SEM),transmission electron microscope (TEM),differential scanning calorimetry(DSC),energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and some otherresearch methods. The main results are summarized as follows:All of the three alloys were typical dentrites structure and maked up of γ phase，γ′phase.There were some mesh-like and radial (γ+γ’) eutectic in interdendrite area.With theincreasing of Ru content, the primary spacing arm tends decreased,the γ/γ′eutectic regionstended to distribute more dispersedly and to be smaller in volume. It was found that andecrease was observed in the degree of elemental segregation with increasing the Ru content.Consequently, the size of γ′phase in dendritic and interdentreat regent became more equable.Ru additions have been increased iquidus temperatures and (γ+γ’) eutectic dissolvetemperatures.The partitioning ratio have been greatly alleviated by increasing the Ru content. Inaddition, the precipitate size decreased with the increasing of Ru addition, furthermore,thediscrepancy in γ′phase of dendritic and interdentreat regent reduced. The investigation of theprolonged aging test at980℃and1070℃suggest that Ru additions increased coarsevelocity and hinder the formation of Topologically-Close-Packed (TCP) precipitates. As theincreasing of Ru content, the time of TCP phase eparate out was leaved, the size and thequantity of the TCP phase was reduced.Tensile properties of alloys have been contrasted with different content of Ru, yieldstrength and tensile strength were increased of Ru addition at the condition of760℃and980℃.The creep properties of three experimental alloys have been improved significantlywith Ru additions. Ru additions increased the creep/stress-rupture life at850℃/650Mpa because Ru enhanced the effect of solution strengthen in middle temperature. Ru additionsincreased the creep/stress-rupture life at1100℃/130Mpa by hinder the formation of TCPphase precipitates. Ru addition can generate denser γ/γ′interfacial dislocation networks andthe average dislocation space because the alloy with higher Ru concentration has a largerlattice mismatch. |
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