Tungsten-rhenium(W-Re)alloys with high-Re contents are the preferred refractory metal materials in many applications because of the improved ductility and processability over pure W and low-Re tung-sten alloys.However...Tungsten-rhenium(W-Re)alloys with high-Re contents are the preferred refractory metal materials in many applications because of the improved ductility and processability over pure W and low-Re tung-sten alloys.However,the sintering concurrently becomes increasingly more difficult with increasing Re contents.Here we proposed that the sintering conundrum is caused by the lowered crystal symmetry and the wider dihedral angle distribution when body-center-cubic(BCC)W is alloyed with more hexagonal-close-packed(HCP)Re,which results in inefficient pore removal in the final stage sintering.We showed that the conundrum can be resolved by pressureless two-step sintering(TSS)which suppresses acceler-ating final-stage grain growth,and our proposal is supported by the data of the critical densityρc that is required to start the second step for successful TSS at different W-Re compositions.Dense ultrafine-grained W-Re alloys with∼300 nm average grain size and up to 25 wt%Re were successfully produced.Our work demonstrates the unique opportunities offered by two-step sintering to advance the scientific understanding and technological practices in powder metallurgy and related fields.展开更多
Warm compression deformation of Fe-13.5%Cr-4.7%Al-2.0%Mo-0.70%Nb-0.40Ta(wt%)(FeCrAl)and Fe-13.5%Cr-4.7%Al-2.0%Mo-0.45%Nb-0.40Ta-0.11Zr(wt%)(FeCrAl-Zr)ferritic stainless steel was performed by a thermal simulation mach...Warm compression deformation of Fe-13.5%Cr-4.7%Al-2.0%Mo-0.70%Nb-0.40Ta(wt%)(FeCrAl)and Fe-13.5%Cr-4.7%Al-2.0%Mo-0.45%Nb-0.40Ta-0.11Zr(wt%)(FeCrAl-Zr)ferritic stainless steel was performed by a thermal simulation machine Gleeble 3800 at 600°C and strain rates of 0.01-10 s^(-1).Before deformation,all the samples were solution-annealed for 2 h at 1150°C for FeCrAl alloy and 1250°C for FeCrAl-Zr alloy.The strain rate has little or no effect on peak stress,and the precipitates in matrix or grain boundary precipitates(GBPs)have no difference in the samples deformed at the strain rate 0.01 s^(-1)and 1 s^(-1)both in FeCrAl and FeCrAl-Zr alloys.The addition of Zr increased the proportion of low-angle grain boundaries(LAGBs).The Laves phase in FeCrAl alloy precipitated uniform in the matrix,while in FeCrAl-Zr alloy Laves phase precipitated at grain boundary and formed GBP.The LAGBs andΣ3 coincident site lattice(CSL)grain boundary both increased in FeCrAl-Zr alloy,which possessed some beneficial properties such as high-temperature creep resistance to the Fe-Cr-Al alloy.More interesting,twins were created by warm deformation,which was difficult in typical bcc ferrite alloy.These results could be expected to provide guidance for subsequent warm working processes for the alloy.展开更多
基金This work is financially supported by National Key R&D Pro-gram of China(no.2022YFB3700075)Natural Science Foundation of China(nos.52074032,51974029,52071013,52130407)+3 种基金Beijing Natural Science Foundation(no.2232084)Guangdong Basic and Applied Basic Research Foundation(no.2021B1515120033)Basic and Applied Basic Research Fund of Guangdong Province(no.BK20BE015)111 Project(no.B170003).
文摘Tungsten-rhenium(W-Re)alloys with high-Re contents are the preferred refractory metal materials in many applications because of the improved ductility and processability over pure W and low-Re tung-sten alloys.However,the sintering concurrently becomes increasingly more difficult with increasing Re contents.Here we proposed that the sintering conundrum is caused by the lowered crystal symmetry and the wider dihedral angle distribution when body-center-cubic(BCC)W is alloyed with more hexagonal-close-packed(HCP)Re,which results in inefficient pore removal in the final stage sintering.We showed that the conundrum can be resolved by pressureless two-step sintering(TSS)which suppresses acceler-ating final-stage grain growth,and our proposal is supported by the data of the critical densityρc that is required to start the second step for successful TSS at different W-Re compositions.Dense ultrafine-grained W-Re alloys with∼300 nm average grain size and up to 25 wt%Re were successfully produced.Our work demonstrates the unique opportunities offered by two-step sintering to advance the scientific understanding and technological practices in powder metallurgy and related fields.
基金This work was financially supported by the National Natural Science Foundation of China(No.U1867201)the Key Project of Nuclear Safety and Advanced Nuclear Technology(No.2019YFB1901002)"the Project supported by State Key Laboratory of Powder Metallurgy",Central South University,Changsha.China.
文摘Warm compression deformation of Fe-13.5%Cr-4.7%Al-2.0%Mo-0.70%Nb-0.40Ta(wt%)(FeCrAl)and Fe-13.5%Cr-4.7%Al-2.0%Mo-0.45%Nb-0.40Ta-0.11Zr(wt%)(FeCrAl-Zr)ferritic stainless steel was performed by a thermal simulation machine Gleeble 3800 at 600°C and strain rates of 0.01-10 s^(-1).Before deformation,all the samples were solution-annealed for 2 h at 1150°C for FeCrAl alloy and 1250°C for FeCrAl-Zr alloy.The strain rate has little or no effect on peak stress,and the precipitates in matrix or grain boundary precipitates(GBPs)have no difference in the samples deformed at the strain rate 0.01 s^(-1)and 1 s^(-1)both in FeCrAl and FeCrAl-Zr alloys.The addition of Zr increased the proportion of low-angle grain boundaries(LAGBs).The Laves phase in FeCrAl alloy precipitated uniform in the matrix,while in FeCrAl-Zr alloy Laves phase precipitated at grain boundary and formed GBP.The LAGBs andΣ3 coincident site lattice(CSL)grain boundary both increased in FeCrAl-Zr alloy,which possessed some beneficial properties such as high-temperature creep resistance to the Fe-Cr-Al alloy.More interesting,twins were created by warm deformation,which was difficult in typical bcc ferrite alloy.These results could be expected to provide guidance for subsequent warm working processes for the alloy.
