Ti−1Al−8V−5Fe(Ti-185)alloy with different iron contents was additively manufactured by electron beam powder bed fusion(EB-PBF),and its microstructure and mechanical properties were investigated.The results show that i...Ti−1Al−8V−5Fe(Ti-185)alloy with different iron contents was additively manufactured by electron beam powder bed fusion(EB-PBF),and its microstructure and mechanical properties were investigated.The results show that increasing the Fe powder content from 4.56 wt.%to 5.98 wt.%(within the specification range)converted coarse columnar prior-βgrains in as-printed alloy into fine equiaxed ones((54.2±32.4)μm)by EB-PBF.However,due to subsequent in-situ precipitation,a micron-thick low-solute weakα-phase became prevalent along each equiaxed grain boundary(GB).This drastically decreased the tensile deformation energy of Ti-185 from 6.2×10^(7)J/m^(3)(columnar grains)to 4.8×10^(7)J/m^(3)(equiaxed grains),despite a mild increase in strength.Fracture characteristics unveiled that the weak GBα-phase is the main crack initiation site and propagation path.展开更多
The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isotherma...The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isothermal aging with considering the influence of alloying elements was investigated.The results show that the coarsening rate of L1_(2)-Ni_(3)Al precipitates increases with co-additions of Ni and Cu,and especially,the increase of Cu content promotes the nucleation of L1_(2)-Ni_(3)Al precipitates.A dynamic competition exists between Lifshitz-Slyozov-Wagner theory and transient interface diffusion-controlled theory for coarsening behavior of L1_(2)-Ni_(3)Al precipitates with duration of isothermal aging.Additionally,the transition from L1_(2)-Ni_(3)Al precipitates to B2-NiAl precipitates during isothermal aging results in the formation of a depleted zone of L1_(2)-Ni_(3)Al precipitates around B2-NiAl precipitates,which inhibits the growth of L1_(2)-Ni_(3)Al precipitates.The coarsening of L1_(2)-Ni_(3)Al precipitates significantly contributes to the yield strength of AFA steels.展开更多
Mg-14Li-1Al （LA141）, LA141-0.3Y, LA141-0.3Sr, and LA141-0.3Y-0.3Sr alloys were prepared in an induction furnace in the argon atmosphere. The microstructures of these alloys were investigated through scanning electro...Mg-14Li-1Al （LA141）, LA141-0.3Y, LA141-0.3Sr, and LA141-0.3Y-0.3Sr alloys were prepared in an induction furnace in the argon atmosphere. The microstructures of these alloys were investigated through scanning electron microscope （SEM）, X-ray diffractometer （XRD） and energy dispersive spectrometer （EDS）. The results show that yttrium and/or strontium additions produce a strong grain refining effect in LA141 alloy. The mean grain sizes of the alloys with addition of Y and/or Sr are reduced remarkably from 600 to 500, 260, 230 μm, respectively. Al 2 Y, Al 4 Sr and Mg 17 Sr 2 phases with different morphologies are verified and exist inside the grain or at the grain boundaries, thus possibly act as heterogeneous nucleation sites and pin up grain boundaries, which restrain the grain growth.展开更多
基金supported by the National Natural Science Foundation of China(No.51829401)the Australian Research Council(No.DP220103407).
文摘Ti−1Al−8V−5Fe(Ti-185)alloy with different iron contents was additively manufactured by electron beam powder bed fusion(EB-PBF),and its microstructure and mechanical properties were investigated.The results show that increasing the Fe powder content from 4.56 wt.%to 5.98 wt.%(within the specification range)converted coarse columnar prior-βgrains in as-printed alloy into fine equiaxed ones((54.2±32.4)μm)by EB-PBF.However,due to subsequent in-situ precipitation,a micron-thick low-solute weakα-phase became prevalent along each equiaxed grain boundary(GB).This drastically decreased the tensile deformation energy of Ti-185 from 6.2×10^(7)J/m^(3)(columnar grains)to 4.8×10^(7)J/m^(3)(equiaxed grains),despite a mild increase in strength.Fracture characteristics unveiled that the weak GBα-phase is the main crack initiation site and propagation path.
基金financial supports from the National Natural Science Foundation of China(Nos.52471004,52171107,52201203)the Industry-University-Research Cooperation Project of Hebei Based Universities and Shijiazhuang City(No.241791237A)the Fundamental Research Funds for the Central Universities(No.N2423030)。
文摘The nano-scale L1_(2)-Ni_(3)Al precipitates significantly contribute to thermal stability of alumina-forming austenitic(AFA)steels.The coarsening behavior of L1_(2)-Ni_(3)Al precipitates in AFA steels during isothermal aging with considering the influence of alloying elements was investigated.The results show that the coarsening rate of L1_(2)-Ni_(3)Al precipitates increases with co-additions of Ni and Cu,and especially,the increase of Cu content promotes the nucleation of L1_(2)-Ni_(3)Al precipitates.A dynamic competition exists between Lifshitz-Slyozov-Wagner theory and transient interface diffusion-controlled theory for coarsening behavior of L1_(2)-Ni_(3)Al precipitates with duration of isothermal aging.Additionally,the transition from L1_(2)-Ni_(3)Al precipitates to B2-NiAl precipitates during isothermal aging results in the formation of a depleted zone of L1_(2)-Ni_(3)Al precipitates around B2-NiAl precipitates,which inhibits the growth of L1_(2)-Ni_(3)Al precipitates.The coarsening of L1_(2)-Ni_(3)Al precipitates significantly contributes to the yield strength of AFA steels.
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2010CSTC-BJLKR)supported by Chongqing Science and Technology Commission, ChinaProject(CDJXS10132203)supported by the Fundamental Research Funds for the Central Universities,China
文摘Mg-14Li-1Al （LA141）, LA141-0.3Y, LA141-0.3Sr, and LA141-0.3Y-0.3Sr alloys were prepared in an induction furnace in the argon atmosphere. The microstructures of these alloys were investigated through scanning electron microscope （SEM）, X-ray diffractometer （XRD） and energy dispersive spectrometer （EDS）. The results show that yttrium and/or strontium additions produce a strong grain refining effect in LA141 alloy. The mean grain sizes of the alloys with addition of Y and/or Sr are reduced remarkably from 600 to 500, 260, 230 μm, respectively. Al 2 Y, Al 4 Sr and Mg 17 Sr 2 phases with different morphologies are verified and exist inside the grain or at the grain boundaries, thus possibly act as heterogeneous nucleation sites and pin up grain boundaries, which restrain the grain growth.
