BFe10-1-1合金管材连续定向凝固制备工艺及组织力学性能

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

采用真空熔炼、Ar气保护下拉式连续定向凝固方法制备了BFe10-1-1合金管材,确定了可获得表面光洁合金管材的工艺参数范围,并对不同制备工艺下合金管材的组织和力学性能进行了研究.结果表明,当冷却水流量、冷却距离和冷却水温度保持不变(分别为900 L/h,8 mm,25℃)时,在熔体温度1250—1280℃和下拉速度0.15—0.45 mm/s的范围内,合理匹配工艺参数,制备了直径10 mm、壁厚1.7 mm,内外表面光洁的柱状晶组织BFe10-1-1合金管材.微观偏析分析表明:主要合金元素中Ni和Fe是负偏析元素,主要富集于枝晶干,而Mn是正偏析元素,主要富集于枝晶间.与普通铸造相比,连续定向凝固方法制备的BFe10-1-1合金管材的偏析程度获得较大改善.合金管材室温拉伸呈典型的韧性断裂,延伸率达到49%,具有优良的塑性变形性能.试样的抗拉强度为212 MPa,显著低于普通铸造合金,有利于合金管材的后续加工成形.

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.