Peritectic Reaction And 3d Microstructures Analysis Of Fe-Ni Peritectic Alloys During Directional Solidification

Recently, Peritectic solidification behavior has drawn much attention . With the development and application of new materials, peritectic reaction can be found in many technologically important materials, such as high temperature structural materials Ti-Al, Ni-Al, Fe-Al alloys, intermetallic compounds, rare earth permanent magnets Nd-Fe-B, Co-Sm-Al alloys, high temperature superconductor Y / Nb-Ba-Cu-O. In the past few decades, people do a lot of work to study peritectic solidification behavior, discovered many new microstructures, achieved many important results, but if want to promote the application of peritectic alloys in engineering as soon as possible also need to do further study.Based on the study to Fe-Ni peritectic alloys of our research group, in this paper, we selection Fe-4.1Ni and Fe-4.4Ni alloy to investigate the peritectic solidification behavior by systematic directional solidification experiments with induction heating. Various microstructures were observed in the directionally solidified samples, such as bands, mixed bands, island banding, tree-like oscillatory pattern, coupled and cellular coupled growth structures, compared with the resistance heating directional solidification experiments results, enriched the solidification theory of Fe-Ni peritectic alloy. Found that, even convective phenomenon existenced, the peritectic reaction is still presence and have an important influence on the formation of the microstructures, summed up the similarities and differences of the peritectic reaction in directional solidification with the resistance heating or induction heating. In addition, this paper using serial sections technique reconstructed 3D morphology of several typical microstructures, including island banding, coupled and cellular coupled growth and dendrite island structures. Verified the true form of the microstructures and discussed the influences of peritectic reaction on various microstructure evolution, avoided the potential errors of two-dimensional analysis. At the same time, reconstructed the single-cell's geometry forms using 3D reconstruction method, accurately measured the diameter and the curvature radius of the cell. The shapes of the cell can be well described by the form of the Saffman-Taylor finger shape equation, validated prediction model. The primary phase re-dissolved because of peritectic reaction,before and after the peritectic reaction primary phaseδdecreased 37.8%, quantitative described the affection of peritectic reaction on cellular peritectic coupled growth. Peritectic reaction also have an important influence on the symbiotic stability of CPCG, mainly reflected in two-phase interface distance l, through quantitative analysis found that l≈2d≈7R, provides datas to validate and improve model of cellular peritectic coupled growth.