Friction stir welding of dissimilar Al/Mg thick plates still faces severe challenges, such as poor formability, formation of thick intermetallic compounds, and low joint strength. In this work, two joint configuration...Friction stir welding of dissimilar Al/Mg thick plates still faces severe challenges, such as poor formability, formation of thick intermetallic compounds, and low joint strength. In this work, two joint configurations, namely inclined butt(conventional butt) and serrated interlocking(innovative butt), are proposed for improving weld formation and joint quality. The results show that a continuous and straight intermetallic compound layer appears at the Mg side interface in conventional butt joint, and the maximum average thickness reaches about 60.1 μm.Additionally, the Mg side interface also partially melts, forming a eutectic structure composed of Mg solid solution and Al_(12)Mg_(17) phase.For the innovative butt joint, the Mg side interface presents the curved interlocking feature, and intermetallic compounds can be reduced to less than 10 μm. The joint strength of innovative butt joint is more than three times that of conventional butt joint. This is due to the interlocking effect and thin intermetallic compounds in the innovative joint.展开更多
An eight year national program aiming at the development of high temperature intermetallics was started by the Agency of Industrial Science and Technology of the Ministry of International Trade and Industry (AIST MITI...An eight year national program aiming at the development of high temperature intermetallics was started by the Agency of Industrial Science and Technology of the Ministry of International Trade and Industry (AIST MITI) in 1989 and almost successfully ended in 1997. This national program with emphasis on basic aspects of the properties and processing of high temperature intermetallics, Ti Al and Nb Al, have given a considerable impetus to intermetallics research in Japan. This is an overview of the results of the program and implications of the program for the future development of high temperature intermetallics compounds for structural applications. Alloy design, evaluation of fundamental mechanical properties, fabrication processing and surface modification have been investigated using these two alloy systems. Based on the obtained results, the concept of alloy design was established, and new technologies, were developed for metal injection moding, casting, rheocasting, sheet casting and rolling, superplastic forming, heat treatment, melting and investment casting, gas atomization, direct rolling of alloyed powders, near net shaping by HIPing alloyed powders and oxidation resistant surface coating. Some of suggested intermetallics alloys are expected to be basics for ultra high temperature structural materials in the next generation because of the extremely high strengths at high temperature, 1 100 ℃ and 1 800 ℃, beyond conventional Ni base superalloys.展开更多
Recent work on Ti_3Al base alloy,TAC-1, developed in CISRI, including investigations of effects of modification in alloying and TMP on microstructural characteristics and mechanical behaviour,indicates that alloy TAC ...Recent work on Ti_3Al base alloy,TAC-1, developed in CISRI, including investigations of effects of modification in alloying and TMP on microstructural characteristics and mechanical behaviour,indicates that alloy TAC -1 is very promising structural material for a number of elevated temperature applications. Stuody dealing with a reverse relation between RT ductility and toughness found on TiA base alloy, TAC-2, led to development of a special heat treatment technique for producing a fine filly lamellar microstructure (FFL), which gives a high and balancing ductility and toughness. This is also of significance for promoting engineering applications of this alloy.展开更多
The microstructures and mechanical properties of Al matrix composites reinforced by different volume fractions of Al-Ni-Co intermetallic particles were investigated.Three different volume fractions of Al-Ni-Co particl...The microstructures and mechanical properties of Al matrix composites reinforced by different volume fractions of Al-Ni-Co intermetallic particles were investigated.Three different volume fractions of Al-Ni-Co particles were added to pure Al matrix using a stir-casting method.Microstructural analysis shows that with the increasing of the reinforcement volume fraction,the matrix grain size decreases and the porosity increases.The mechanical properties of the composites are improved over the matrix materials,except for the decreasing of the ductility.Fracture surface examination indicates that there is a good interfacial bonding between the Al matrix and the Al-Ni-Co particles and the fracture initiation does not occur at the particle-matrix interface.展开更多
A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld mi...A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.展开更多
Research on high temperature wear mechanism shows that the oxidation and corrosion resistance, high temperature hardness, thermal fatigue resistance and structure stability are main control factors for Ni_3Al based al...Research on high temperature wear mechanism shows that the oxidation and corrosion resistance, high temperature hardness, thermal fatigue resistance and structure stability are main control factors for Ni_3Al based alloys. Some important workpieces have been produced in mass quantity such as the guide shoe used in wire hot rolling. Ni_3Al based alloys could be used as cavitation erosion resistant materials mainly because of their high temperature mechanical properties, high work hardening ability and fatigue resistance. The weld electrode of Ni_3Al based alloy has been fabricated and used in the protection against cavitation erosion of big blade of hydraulic turbine in Sanmenxia Hydropower Station. Ni_3Al based alloys exhibit superproperties in the situation of high temperature over 1200℃, for example, in the work condition of flame tube of jet. Some of rivets used in combustor of jet are fabricated and tested.展开更多
In-situ alloy development during surface processing allows for a limitless materials selection to protect components exposed to severe service conditions. In fact surface alloying offers the possibility to strengthen ...In-situ alloy development during surface processing allows for a limitless materials selection to protect components exposed to severe service conditions. In fact surface alloying offers the possibility to strengthen surface components with alloys that would not be possible to process otherwise. This work used Plasma transferred arc (PTA) hardfacing for surface alloying. Different amounts of aluminium powder, 5-25%, were added to a Ni based superalloy, from Hastealloy C family, in the atomized form. The mixture was homogeneized in a ball mill and PTA deposited on carbon steel substrate. The influence of different processing parameters on the final surface alloy was evaluated as current intensity and depositing velocity were varied. Coatings were characterized by optical and scanning electronic microscopy, X-ray diffraction and Vickers microhardness profiles, under a 500g load. Results showed that PTA hardfacing is an adequate surface alloying. For the conditions tested increasing hardness was obtained by solid solution for the lower amounts of Al added and due to the new intermetallic phases for the richer Al mixture.展开更多
基金supported by the National Natural Science Foundation of China (No.51874179,52005240 and 52164045)the Young Talent Program of Major Disciplines of Academic and Technical Leaders in Jiangxi Province (No.20212BCJ23028)。
文摘Friction stir welding of dissimilar Al/Mg thick plates still faces severe challenges, such as poor formability, formation of thick intermetallic compounds, and low joint strength. In this work, two joint configurations, namely inclined butt(conventional butt) and serrated interlocking(innovative butt), are proposed for improving weld formation and joint quality. The results show that a continuous and straight intermetallic compound layer appears at the Mg side interface in conventional butt joint, and the maximum average thickness reaches about 60.1 μm.Additionally, the Mg side interface also partially melts, forming a eutectic structure composed of Mg solid solution and Al_(12)Mg_(17) phase.For the innovative butt joint, the Mg side interface presents the curved interlocking feature, and intermetallic compounds can be reduced to less than 10 μm. The joint strength of innovative butt joint is more than three times that of conventional butt joint. This is due to the interlocking effect and thin intermetallic compounds in the innovative joint.
文摘An eight year national program aiming at the development of high temperature intermetallics was started by the Agency of Industrial Science and Technology of the Ministry of International Trade and Industry (AIST MITI) in 1989 and almost successfully ended in 1997. This national program with emphasis on basic aspects of the properties and processing of high temperature intermetallics, Ti Al and Nb Al, have given a considerable impetus to intermetallics research in Japan. This is an overview of the results of the program and implications of the program for the future development of high temperature intermetallics compounds for structural applications. Alloy design, evaluation of fundamental mechanical properties, fabrication processing and surface modification have been investigated using these two alloy systems. Based on the obtained results, the concept of alloy design was established, and new technologies, were developed for metal injection moding, casting, rheocasting, sheet casting and rolling, superplastic forming, heat treatment, melting and investment casting, gas atomization, direct rolling of alloyed powders, near net shaping by HIPing alloyed powders and oxidation resistant surface coating. Some of suggested intermetallics alloys are expected to be basics for ultra high temperature structural materials in the next generation because of the extremely high strengths at high temperature, 1 100 ℃ and 1 800 ℃, beyond conventional Ni base superalloys.
文摘Recent work on Ti_3Al base alloy,TAC-1, developed in CISRI, including investigations of effects of modification in alloying and TMP on microstructural characteristics and mechanical behaviour,indicates that alloy TAC -1 is very promising structural material for a number of elevated temperature applications. Stuody dealing with a reverse relation between RT ductility and toughness found on TiA base alloy, TAC-2, led to development of a special heat treatment technique for producing a fine filly lamellar microstructure (FFL), which gives a high and balancing ductility and toughness. This is also of significance for promoting engineering applications of this alloy.
基金Project(50571081)supported by the National Natural Science Foundation of ChinaProject(04G53024)supported by the Aviation Foundation of China
文摘The microstructures and mechanical properties of Al matrix composites reinforced by different volume fractions of Al-Ni-Co intermetallic particles were investigated.Three different volume fractions of Al-Ni-Co particles were added to pure Al matrix using a stir-casting method.Microstructural analysis shows that with the increasing of the reinforcement volume fraction,the matrix grain size decreases and the porosity increases.The mechanical properties of the composites are improved over the matrix materials,except for the decreasing of the ductility.Fracture surface examination indicates that there is a good interfacial bonding between the Al matrix and the Al-Ni-Co particles and the fracture initiation does not occur at the particle-matrix interface.
基金Supported by National Natural Science Foundation of China(Grant Nos.52275349,52035005)Key Research and Development Program of Shandong Province of China(Grant No.2021ZLGX01)Qilu Young Scholar Program of Shandong University of China.
文摘A novel double side friction stir Z shape lap-butt welding(DS-FSZW)process was proposed to achieve excellent mechanical properties of Al/Cu medium-thick dissimilar joints.The influence of welding parameters on weld microstructure and properties of DS-FSZW joint were systematically investigated.It indicated that defect-free medium-thick Al/Cu DS-FSZW joint could be achieved under an optimal welding parameter.DS-FSZW joint was prone to form void defects in the bottom of the second-pass weld.The recrystallization mechanisms at the top and middle of the weld nugget zone(WNZ)were continuous dynamic recrystallization(CDRX)and geometric dynamic recrystallization(GDRX).While the major recrystallization mechanism at the bottom of the WNZ was GDRX.DS-FSZW joint of the optimal welding condition with 850 r/min-400 mm/min was produced with a continuous thin and crack-free IMCs layer at the Al/Cu interface,and the maximum tensile strength of this joint is 160.57 MPa,which is equivalent to 65.54%of pure Cu base material.Moreover,the corrosion resistance of Al/Cu DS-FSZW joints also achieved its maximum value at the optimal welding parameter of 850 r/min-400 mm/min.It demonstrates that the DS-FSZW process can simultaneously produce medium-thick Al/Cu joints with excellent mechanical performance and corrosion resistance.
基金financially supported by the Russian Science Foundation(No.20-19-00746)(SEM,DSC,thermodynamic calculations)the federal academic leadership program Priority 2030 of NUST MISIS(DFT,XRD)。
基金the High Technology Research and Development Programme of China
文摘Research on high temperature wear mechanism shows that the oxidation and corrosion resistance, high temperature hardness, thermal fatigue resistance and structure stability are main control factors for Ni_3Al based alloys. Some important workpieces have been produced in mass quantity such as the guide shoe used in wire hot rolling. Ni_3Al based alloys could be used as cavitation erosion resistant materials mainly because of their high temperature mechanical properties, high work hardening ability and fatigue resistance. The weld electrode of Ni_3Al based alloy has been fabricated and used in the protection against cavitation erosion of big blade of hydraulic turbine in Sanmenxia Hydropower Station. Ni_3Al based alloys exhibit superproperties in the situation of high temperature over 1200℃, for example, in the work condition of flame tube of jet. Some of rivets used in combustor of jet are fabricated and tested.
文摘In-situ alloy development during surface processing allows for a limitless materials selection to protect components exposed to severe service conditions. In fact surface alloying offers the possibility to strengthen surface components with alloys that would not be possible to process otherwise. This work used Plasma transferred arc (PTA) hardfacing for surface alloying. Different amounts of aluminium powder, 5-25%, were added to a Ni based superalloy, from Hastealloy C family, in the atomized form. The mixture was homogeneized in a ball mill and PTA deposited on carbon steel substrate. The influence of different processing parameters on the final surface alloy was evaluated as current intensity and depositing velocity were varied. Coatings were characterized by optical and scanning electronic microscopy, X-ray diffraction and Vickers microhardness profiles, under a 500g load. Results showed that PTA hardfacing is an adequate surface alloying. For the conditions tested increasing hardness was obtained by solid solution for the lower amounts of Al added and due to the new intermetallic phases for the richer Al mixture.
