Nanlin SHI
,
Jiwei FENG
,
Yanfen GUO
,
Yuyin LIU
,
Z.X.Guo
材料科学技术（英文）
Prenitridation of the TiBx coating surface of the Sigma SM1240 SiC fiber can form more stable compounds at the surface and obstruct the release of boron atoms into the Ti-based alloy matrix. The effect of nitridation on the tensile strength of the fiber was investigated in this work. Nitridation could degrade the tensile strength of the SiC fiber if the treating temperature and time are not optimized. The chemical reaction between the W core and SiC and the modification of fiber microstructure during the nitridation are responsible for the degradation in strength. The strength can be maintained by further optimization of the treating temperature and time. Therefore, stabilizing the surface of TiBx coating and hence the interface of the SiCf/Ti composite by the nitridation of the SiC fiber is a feasible technique for practical applications.
关键词:
SiC fiber
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null
,
null
,
null
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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:
Jun ZHANG
,
Qingjiang WANG
,
Yuyin LIU
,
Li LI
,
Dong LI
材料科学技术（英文）
The characteristic of the precipitation and growth of α2 ordered phase during aging treatment in near αTi alloys have been investigated in terms of the influences of aging temperature, aging time and aging manner. The results exhibit that aging temperatures influence the distribution ofα2 phase precipitated and cause the changes in growth speed ofα2 phase. For various aging temperatures, the time to finish precipitation ofα2 phase is different. The facts that various distribution characteristics and growth speed ofα2 ordered phase are caused by changed aging condition imply optimal selection and control for precipitation ofα2 ordered phase reachable. Some discussions on adoptable aging steps are presented.
关键词:
α2 ordered phase
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null
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