FABRICATION PROCESS,MICROSTRUCTURE AND MECHANICAL PROPERTIES OF BFe10-1-1 ALLOY TUBES BY CONTINUOUS UNIDIRECTIONAL SOLIDIFICATION

BFe10-1-1 cupronickel alloy tubes were fabricated by the vertical downward continuous unidirectional solidification with vacuum melting and argon-shield.The effects of processing parameters on the surface quality of alloy tubes have been investigated,and the microstructure and mechanical properties of cupronickel alloy tubes were characterized.The results show that BFe10-1-1 cupronickel alloy tubes having smooth surface and columnar crystal structure,with a diameter of 10 mm and thickness of 1.7 mm could be fabricated at a range of melting temperatures from 1250℃to 1280℃matching well with the withdrawal speed range from 0.15 mm/s to 0.45 mm/s on the conditions of cooling water flow volume 900 L/h,cooling distance 8 mm and cooling water temperature 25℃.The segregation ratio of Mn is larger than one,indicating the Mn tends to partition preferentially to the interdendritic region,whereas Ni and Fe to dendritic structure.Comparing with alloys fabricated by traditional casting,the degree of microsegregation of the alloy fabricated by continuous unidirectional solidification is reduced.The elongation of 49%at room temperature for the fabricated cupronickel alloy tubes exhibits excellent plastic deformation property.BFe10-1-1 cupronickel alloy tubes fabricated by the continuous unidirectional solidification have the tensile strength of 212 MPa which is markedly reduced compared with cupronickel alloys produced by conventional casting,and are particularly advantageous to subsequent processing.