Cu合金在电弧熔丝增材制造过程中的组织与力学性能演化

Evolution in microstructure and mechanical properties of Cu alloy during wire and arc additive manufacture

本文研究了Cu-8Al合金在电弧熔丝增材制造过程中的微观组织、物相、显微硬度和拉伸性能的演化行为。结果表明,刚沉积的CuAl合金晶粒为尺寸较大的枝晶,在后道次的热影响作用下转变成较细小的柱状晶,而后柱状晶长大,直到晶粒尺寸在距样品端部几毫米的位置趋于稳定。刚沉积的CuAl合金发生Al的枝晶偏析,但在后道次热影响的作用下偏析可消除,使合金组织和成分均匀化。板状样品端部即最后沉积未受后续热影响的位置显微硬度高达HV 160,但随着Al偏析的消除以及枝晶转变成柱状晶,硬度降低到HV 80。原位拉伸结果显示CuAl合金板的抗拉强度高达400 MPa,伸长率可达50%,其屈服强度还有一定的提升空间。拉伸过程中原位观察到了位错滑移和晶粒转动,断裂机制总体为韧窝断裂,端部屈服强度更高、塑性略低、晶粒转动更普遍。总体上电弧熔丝增材制造的CuAl合金板除端部之外组织均匀,具备良好的力学性能。如需其组织性能均匀,或要求高耐蚀性,有必要在沉积后对端部进行局部热处理;如需更好的耐磨性能则不需处理。可进一步添加少量析出强化元素提高CuAl合金的强度与耐磨性能。

In this study,the evolution in microstructure,phase,microhardness and tensile behavior of a Cu-8Al alloy plate during the wire and arc additive manufacture(WAAM)process were investigated.The results reveal that the asdeposited CuAl alloy is composed of coarse dendrites,which gradually transform into relatively fine columnar grains under heat effect,and then the size of the columnar grains increases until becomes stable at the location a few millimeters from the top of the plate.Dendrite segregation of Al exists at the as-deposited region and can be eliminated under heateffect of the later passes,resulting in homogenization of composition and microstructure.The microhardness at the plate top is about HV160,but decreases sharply to about HV80 when the Al segregation is eliminated and the dendrites transform.In-situ tensile tests reveal that the CuAl plate shows high tensile strength(~400 MPa)and high elongation(~50%).Both dislocation slip and grain rotation were observed during the tensile process,and all the specimens showed a dimple fracture mode.Generally,the thin-walled CuAl alloy plate prepared by WAAM is uniform and shows high mechanical property,while a local post heat treatment at relative low temperature is necessary in some conditions.