Limin DONG
,
Rui YANG
材料科学技术（英文）
The influences of alloying elements W, Mo, Cr, and Nb on retained β phase in 47Al based near γ-TiAl alloys have been studied. The results reveal that the amount of retained β phase is increased by the addition of Cr, Mo, W in rising rank, although the distribution of β phase in Cr-bearing alloys is different from that of Mo- or W-bearing alloys. For Nb-doped alloys, no retainedβwas found even when 5 at.pct Nb was added. The as-cast microstructural features and the distribution of theβphase in the different alloy families were compared and interpreted in terms of the different segregation behaviour of these elements in Ti.
关键词:
γ-TiAl
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null
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null
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null
Wei JIN
,
Mingzhou GAO
,
Rui YANG
,
Zhuangqi HU
材料科学技术（英文）
The recovery strain, stress and transformation temperature of different pre-strained specimens of Ti44Ni47Nb9 were investigated by tensile test and electrical resistance measurement. The results indicated that pre-strain increases the reverse martensitic transformation temperature (A ' (s)) and hysteresis (A(s) - M-s). The recovery strain and stress are higher if the specimens are pre-strained between M-s and A(s) temperature than outside this temperature range. There exists an optimal pre-strain value, about 10%, at which the specimen exhibits maximum recovery strain and stress.
关键词:
Ping PENG
,
Caixing ZHENG
,
Shaochang HAN
,
Zhaohui JIN
,
Rui YANG
,
Zhuangqi HU
材料科学技术（英文）
The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Al interface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was found that the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand, less than -0.6% negative lattice misfit can promote the binding strength of γ/ interface. On the other hand, the total bonding strength ofγ/ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must be carefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structural stability ofγ/ interface when one designs a new Ni-base single crystal superalloy.
关键词:
γ/ interface
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null
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null
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null
Wenbin SHENG
,
Dong LI
,
Rui YANG
,
Yuyin LIU
,
Jingjie GUO
,
Jun JIA
材料科学技术（英文）
Ti-48Al-2Cr-2Nb automobile exhaust valves were formed with permanent mold centrifugal cast method and their surface layer structure, microstructure, elements distribution and mechanical properties were analyzed by SEM, XRD and EMPA etc. Furthermore, the HIPped valves were tested on 483Q diesel engine. Results showed that the element distribution of TiAl based alloy exhaust valves was uniform and their microstructure was refined. The typical mechanical properties of HiPped exhaust valves were sigma (b)=670 MPa, sigma (0.2)=527.5 MPa and delta =3%. Engine test showed that the valves had excellent airtightness and wear resistance properties and satisfied the requirements of engine successfully.
关键词:
Yulin HAO
,
Rui YANG
,
Yuyou CUI
,
Dong LI
,
Wanfu GAO
材料科学技术（英文）
Room temperature compression properties of Ti-51Al-(1-2)X and Ti-26Al-(1-2)X alloys (X = V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Ta, Ga or Sn) were measured in oder to examine how the compression deformability correlates with the site occupancies of the alloying elements in γ-TiAl and α2-Ti3Al. The results showed that, for the γ phase, the compression ratio is not related to the site preference of the alloying elements in a simple way. For the α2 phase, the following correlation was observed between the compression ratio and the site occupancies of the investigated elements, those which occupy Al sites decrease the deformability, while those occupying Ti sites (except V) improve the deformability of the α2 phase. Compression properties of dual-phase TiAl alloys based on Ti-46Al-(1, 3, 5)X were also measured at room temperature to test a hypothetical mechanism of ductilization based on mechanical compatibility at phase interface. It was concluded that no simple relationship exists between the deformability of the dual-phase alloys and the properties of their constituent phases.
关键词:
Yanhua LI
,
Nanlin SHI
,
Dezhi ZHANG
,
Rui YANG
材料科学技术（英文）
A continuous loading push-out test technique was used to measure the interfacial shear strength of SiC fiber reinforced Ti matrix composites. The interfacial shear strength of samples as-fabricated and after heat exposed at 700 and 800℃ for 50 h was successfully determined. It has been found that the interfacial shear strength of the specimen exposed at 700℃ was higher than that of as-prepared and exposed samples at 800℃. The shear strength of the as-prepared samples was about 112.45 MPa, and increased to about 153.77 MPa after heat-treating at 700℃ for 50 h, but decreased to 133.11 MPa after treating at 800℃ for 50 h. Scanning electron microscope (SEM) was used to investigate the interfacial morphology of the samples. The brittle phase was the main products of interface for samples exposed at 800℃, and the interface was easily peeled off.
关键词:
Push-out test
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null
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null
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null
Wei JIN
,
Mingzhou CAO
,
Rui YANG
,
Zhuangqi HU
,
Shaoyu QIU
,
Hong ZOU
材料科学技术（英文）
The effect of heat treatment on martensitic transformation behavior has been investigated in Ti44Ni47Nb9 alloy. The relation between transformation temperatures and critical stress of stress induced martensitic transformation is interpreted in terms of thermodynamic theory. It is shown that the decrease in transformation temperature in specimens of slow cooling rate or low temperature aging after solution heat treatment results from the changes of Ni/Ti ratio in the matrix. The increase of critical stress of stress induced martensitic transformation is a consequence of the decrease of transformation temperatures.
关键词:
Ti44Ni47Nb9 shape memory alloy
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null
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null
Wei JIN
,
Ying YAN
,
Jian WANG
,
Mingzhou CAO
,
Rui YANG
材料科学技术（英文）
The mechanical behavior and the effect of pre-strain on recovery behavior of Ti50Ni47Fe3 (at. pct) alloy were investigated systematically by tensile and recovered tests accompanied by electrical resistance measurement. Ti50Ni47Fe3 alloy has different deformation behaviors at different temperature ranges, the deformation curves in different temperature range can be classified into four kinds. The start temperature of recovery increases with the increase of pre-strain. There exists an optimal deformation condition, at which the specimen exhibits maximum free recovery strain. With increasing pre-strain the recovery stress increases and reaches the maximum at 8% pre-strain. R-phase to parent transition offered about 0.2% recovery strain. With pre-strain increasing the recovery stress increases and reaches to the maximum at 8% pre-strain. The recovery stress is corresponding with the critical stress of stress-induced martensitic transformation.
关键词:
Deformation
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null
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null
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null
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