The active eutectoid decomposition and its morphological evolution during slow cooling and isothermal holding were investigated in a Ru-containing Ti Al alloy. The fine τ 1/γ active eutectoid nodules precipitated at...The active eutectoid decomposition and its morphological evolution during slow cooling and isothermal holding were investigated in a Ru-containing Ti Al alloy. The fine τ 1/γ active eutectoid nodules precipitated at α grain boundary and interior during water quenching. The active eutectoid microstructure evolved from sheaf-like, granular to bulky net-like sluggish eutectoid morphology gradually with the decrease in quenching/holding temperatures. The active eutectoid reaction occurs from 1220 to 1290 ℃, while the beginning temperature of sluggish eutectoid locates at 1305 ± 5 ℃. The combination of the intact τ_(1) phase and immature nano-sized γ laths suggests a short incubation period of τ_(1) phase in the active type. Furtherly, the semiquantitative estimation shows that the growth velocity of active eutectoid is about ninety times higher than sluggish type. In addition, a representative feature of γ phase abruptly ripening along {111} crystallographic plane was also observed in the active eutectoid.展开更多
Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloy...Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloys was improved by hot deformation.The different deformation behaviors of reinforcements from traditional alloys,including the eutectoid decomposition ofβ-Nb_(5)Si_(3),and the stacking faults(SFs)and reorientation-induced plasticity(RIP)effect of Nb_(4)FeSi,are revealed.During hot deformation,theβ-Nb_(5)Si_(3)phase undergoes the eutectoid decomposition to obtain theα-Nb_(5)Si_(3)and niobium-based solid solutions(Nbss)phases,whichα-Nb_(5)Si_(3)and Nbss satisfy the relationship{110}_(α)//{110}_(Nbss).The[110]SFs and lath-like reoriented variants are formed in the Nb_(4)FeSi phase,where the matrix and variants follow[001]_(m)//[111]v,(110)_(m)//(110)v.Furthermore,the interface between matrix and variant isΣ33c symmetrical tilt boundaries,manifested as(110)/60°.The fracture toughness of the deformed alloy reaches 18.31 MPa·m1/2 at 1300℃/0.005 s^(-1)/0.7,which is 49%higher than the initial alloy.展开更多
Thermohydrogen treatment （THT） is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with di...Thermohydrogen treatment （THT） is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with different hydrogen contents and processed solution aging. Accordingly, the microstructure evolution and phase transformation were analyzed. Results show that during solution aging, eutectoid decomposition occurs and the product is a mixture of coarse primaryα, fine eutectoid product and undecomposed βH. The size of primary α is closely dependent on the hydrogen content, and large primary α can be obtained at medium hydrogen content. Further, the influence of hydrogen content on the growth of primary α phase was revealed. The primary α is much fine, and the eutectoid product is relatively homo- geneous with 0.984 wt% H. After THT, the ultimate strength is beyond 1,100 MPa that has increased by 23.15% compared with that in as-cast state.展开更多
The eutectoid decomposition reaction that occurred in RECo5 phases（RE=Dy and Gd ） at low temperature was discussed and confirmed by X-ray powder diffraction（XRD）, differential thermal analysis, and scanning electr...The eutectoid decomposition reaction that occurred in RECo5 phases（RE=Dy and Gd ） at low temperature was discussed and confirmed by X-ray powder diffraction（XRD）, differential thermal analysis, and scanning electron microscopy.The decomposition temperature of the GdCo5 and DyCo5 were identified as 805.8 and 900 °C, respectively.The GdCo5 and DyCo5 phases could not be found in the isothermal section of Gd-Dy-Co ternary system at 800 K.Reasons for the absence of the RE2Co7 phase in the XRD patterns were discussed in detail.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51774238)the 2018 joint Foundation of Ministry of Education for Equipment Preresearch(No.6141A020332)。
文摘The active eutectoid decomposition and its morphological evolution during slow cooling and isothermal holding were investigated in a Ru-containing Ti Al alloy. The fine τ 1/γ active eutectoid nodules precipitated at α grain boundary and interior during water quenching. The active eutectoid microstructure evolved from sheaf-like, granular to bulky net-like sluggish eutectoid morphology gradually with the decrease in quenching/holding temperatures. The active eutectoid reaction occurs from 1220 to 1290 ℃, while the beginning temperature of sluggish eutectoid locates at 1305 ± 5 ℃. The combination of the intact τ_(1) phase and immature nano-sized γ laths suggests a short incubation period of τ_(1) phase in the active type. Furtherly, the semiquantitative estimation shows that the growth velocity of active eutectoid is about ninety times higher than sluggish type. In addition, a representative feature of γ phase abruptly ripening along {111} crystallographic plane was also observed in the active eutectoid.
基金supported by the National Natural Science Foundation of China(Nos.52425401 and 52374384)the Foundation of National Key Laboratory for Precision Hot Processing of Metals(No.JCKYS2021603C001)the Fundamental Research Funds for the Central Universities(No.2023FRFK06014).
文摘Nb-Si-based in situ composites are receiving attention as a substitute for Ni-based alloys in aerospace,while poor toughness limits its application.In this work,the toughness of Nb_(4)FeSi-containing Nb-Si-based alloys was improved by hot deformation.The different deformation behaviors of reinforcements from traditional alloys,including the eutectoid decomposition ofβ-Nb_(5)Si_(3),and the stacking faults(SFs)and reorientation-induced plasticity(RIP)effect of Nb_(4)FeSi,are revealed.During hot deformation,theβ-Nb_(5)Si_(3)phase undergoes the eutectoid decomposition to obtain theα-Nb_(5)Si_(3)and niobium-based solid solutions(Nbss)phases,whichα-Nb_(5)Si_(3)and Nbss satisfy the relationship{110}_(α)//{110}_(Nbss).The[110]SFs and lath-like reoriented variants are formed in the Nb_(4)FeSi phase,where the matrix and variants follow[001]_(m)//[111]v,(110)_(m)//(110)v.Furthermore,the interface between matrix and variant isΣ33c symmetrical tilt boundaries,manifested as(110)/60°.The fracture toughness of the deformed alloy reaches 18.31 MPa·m1/2 at 1300℃/0.005 s^(-1)/0.7,which is 49%higher than the initial alloy.
文摘Thermohydrogen treatment （THT） is an effective way to refine microstructure and improve the mechanical properties of the titanium alloys. In the current work, as-cast Ti-6.5Al-2Zr-Mo-V alloy was hydrogenated with different hydrogen contents and processed solution aging. Accordingly, the microstructure evolution and phase transformation were analyzed. Results show that during solution aging, eutectoid decomposition occurs and the product is a mixture of coarse primaryα, fine eutectoid product and undecomposed βH. The size of primary α is closely dependent on the hydrogen content, and large primary α can be obtained at medium hydrogen content. Further, the influence of hydrogen content on the growth of primary α phase was revealed. The primary α is much fine, and the eutectoid product is relatively homo- geneous with 0.984 wt% H. After THT, the ultimate strength is beyond 1,100 MPa that has increased by 23.15% compared with that in as-cast state.
基金supported by the National Natural Science Foundation of China (50471108)the Natural Science Foundation of Guangxi (0448022, 0540009, 0640040)Key Project of Guangxi University for Nationality (2007, 2008)
文摘The eutectoid decomposition reaction that occurred in RECo5 phases（RE=Dy and Gd ） at low temperature was discussed and confirmed by X-ray powder diffraction（XRD）, differential thermal analysis, and scanning electron microscopy.The decomposition temperature of the GdCo5 and DyCo5 were identified as 805.8 and 900 °C, respectively.The GdCo5 and DyCo5 phases could not be found in the isothermal section of Gd-Dy-Co ternary system at 800 K.Reasons for the absence of the RE2Co7 phase in the XRD patterns were discussed in detail.
