钛及其合金的粉末床熔融式(PBF)增材制造技术因具有定制制造、成本节约和时间优化等优势,在航空以及生物医学领域备受关注。但在PBF制造钛合金时,多种因素如热导率低、热积累、氧化敏感性及快速冷却引起的热应力共同导致成形件缺陷、组...钛及其合金的粉末床熔融式(PBF)增材制造技术因具有定制制造、成本节约和时间优化等优势,在航空以及生物医学领域备受关注。但在PBF制造钛合金时,多种因素如热导率低、热积累、氧化敏感性及快速冷却引起的热应力共同导致成形件缺陷、组织差异、性能不稳定与质量参差不齐等问题。因此,本文通过调研PBF技术中的激光粉末床熔融(Laser powder bed fusion,L-PBF)和电子束粉末床熔融(Electron beam powder bed fusion,EB-PBF)技术原理,讨论PBF增材制造钛合金微观组织特征、力学性能、耐腐蚀性能、耐磨损性能与生物相容性的特点;同时,聚焦成形过程中的缺陷形成机理及影响,提出缺陷消除方法;最后,展望两种技术的未来发展方向,为促进创新钛合金增材制造提供新的研究思路。展开更多
The effects of solidification variables on the as-cast microstructures of nickel-base single crystal superalloy DD3 have been investigated by using the modified Bridgman apparatus. The experiments were performed under...The effects of solidification variables on the as-cast microstructures of nickel-base single crystal superalloy DD3 have been investigated by using the modified Bridgman apparatus. The experiments were performed under a thermal gradient of approximately 45 K.cm-1 and at withdrawal rates ranging from 30 to 200 m.s-1. The experimental results show that the primary and secondary dendritic arm spacings （PDAS and SDAS） decrease when the withdrawal rate is increased. Compared with the theoretical models of PDAS, the results are in good agreement with Trivedi＇s model. The relationships of PDAS and SDAS with withdrawal rates can be described as ;λ1 = 649.7V-0.24±0.02 and λ2 = 281 V-0.32±0.03, respectively. In addition, the size of the λ2 phase significantly decreases with increasing withdrawal rate.展开更多
The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amou...The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.展开更多
文摘钛及其合金的粉末床熔融式(PBF)增材制造技术因具有定制制造、成本节约和时间优化等优势,在航空以及生物医学领域备受关注。但在PBF制造钛合金时,多种因素如热导率低、热积累、氧化敏感性及快速冷却引起的热应力共同导致成形件缺陷、组织差异、性能不稳定与质量参差不齐等问题。因此,本文通过调研PBF技术中的激光粉末床熔融(Laser powder bed fusion,L-PBF)和电子束粉末床熔融(Electron beam powder bed fusion,EB-PBF)技术原理,讨论PBF增材制造钛合金微观组织特征、力学性能、耐腐蚀性能、耐磨损性能与生物相容性的特点;同时,聚焦成形过程中的缺陷形成机理及影响,提出缺陷消除方法;最后,展望两种技术的未来发展方向,为促进创新钛合金增材制造提供新的研究思路。
基金supported by the National Basic Research Program of China(Nos.2010CB631202 and 2011CB610406)the National Natural Science Foundation of China(Nos.50827102,51171151 and 50931004)+1 种基金the Aeronautical Science Foundation of China(No.2010ZE53048)the China Post-doctoral Science Foundation Funded Project(No.20100481361)
文摘The effects of solidification variables on the as-cast microstructures of nickel-base single crystal superalloy DD3 have been investigated by using the modified Bridgman apparatus. The experiments were performed under a thermal gradient of approximately 45 K.cm-1 and at withdrawal rates ranging from 30 to 200 m.s-1. The experimental results show that the primary and secondary dendritic arm spacings （PDAS and SDAS） decrease when the withdrawal rate is increased. Compared with the theoretical models of PDAS, the results are in good agreement with Trivedi＇s model. The relationships of PDAS and SDAS with withdrawal rates can be described as ;λ1 = 649.7V-0.24±0.02 and λ2 = 281 V-0.32±0.03, respectively. In addition, the size of the λ2 phase significantly decreases with increasing withdrawal rate.
基金Funded in Part by the Fundamental Research Funds for the Central Universities(Nos.300102318205,310831161020,310831163401)the National Natural Science Foundation of China(No.51301021)+2 种基金the China Postdoctoral Science Foundation(No.2016M592730)the Innovation and Entrepreneurship Training Program of Chang’an University(No.201610710084)the Fund of the State Key Laboratory of Solidification and Processing in Northwestern Polytechnical University(No.SKLSP201302)
文摘The parameters for the electro-deposition of Cu were optimized in order to increase the compressive properties of close cell aluminum. Different values of deposition voltages and times were considered to vary the amount of deposited Cu. The surface morphology of the coating was observed by SEM and the compressive properties were evaluated by MTS. The results show that the coating is more homogeneous and compact with increasing voltage in a certain range, and beyond which, the coating quality decreases apparently. The reason is dedicated to the discharge rate of Cu2+ and nucleus formed in unit time. The compression results show three experienced stages: elastic deformation stage, collapse deformation stage and densification stage. After the electro-deposition of Cu, the elasticity modulus is increased obviously and the platform stress is also increased. Under the same strain, the stress of the aluminum foam with coating is reinforced comparing with the aluminum foam without coating. Furthermore, the platform area is widened apparently. In addition, Cu-SiC nanocomposite coatings are electrodeposited in alumium foams for further improving the mechanical characterization.
