Research and development efforts are still very active on 718-type alloys although two major members of this widely used family, 718 and 625, were invented almost a half-century ago. Emphasis in this type of work at A...Research and development efforts are still very active on 718-type alloys although two major members of this widely used family, 718 and 625, were invented almost a half-century ago. Emphasis in this type of work at ATI Allvac is directed at improving existing alloys and developing new alloys to meet ever-increasing industrial demands. The improvement of existing alloys is exemplified by addition of minor elements P and B in alloy 718. The discovery of the beneficial effect of P and B in wrought alloy 718 led to development of a new, modified alloy, AllvacH 718 ERR. A large effort has also been directed at studying the effects of major element modifications in 718-type alloys, and a new alloy, AllvacR 718PlusTM, has been developed. The new alloy has much better high temperature capability, especially thermal stability, approaching the level of Waspaloy but retains excellent processing characteristics, similar to alloy 718. Alloy 718PlusTM should be useful in any 718-type application requiring a higher working temperature. The properties and processing of this alloy are introduced in this paper.展开更多
Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. Th...Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. The result shows that the DRZ, the mixture of TiAl3 and Al, grows layer by layer along their chemical equilibrium zone. In the course, the growth interface moves toward the aluminum side. TiAl3 is the only new phase which forms earliest in the course of heat-treatment. The growth mechanism of the DRZ changes after the phase transition of titanium. Before the phase transition of titanium, the growth of the DRZ is controlled by the dissolution speed of the titanium to the molten aluminum, while after the phase transition of titanium, the growth is controlled by the chemical reaction speed of Al and Ti atoms, and consequently, its growth rate is greatly increased.展开更多
Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-S...Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.展开更多
Friction stir welding(FSW)was performed to produce Al/Ti lap joints under various welding conditions.More heat was generated when rotational rate increased or traversing rate decreased.Two types of Al/Ti interfaces–m...Friction stir welding(FSW)was performed to produce Al/Ti lap joints under various welding conditions.More heat was generated when rotational rate increased or traversing rate decreased.Two types of Al/Ti interfaces–mixed interface and diffusive interface–were formed under different welding conditions.The diffusive interface was formed with low heat input,and the mixed interface was formed more heat.The grains at the mixed interface were larger than those at the diffusive interface because of the higher heat input.Moreover,the microstructure of the mixed interface had a lower texture intensity compared with that of the diffusive interface,which was attributed to the enhanced continuous dynamic recrystallization(CDRX).TiAl3 was formed at the diffusive interface.When the interface varied to the mixed interface as heat input increased,TiAl was fomed within the Al/Ti mixture following the formation of TiAl3.In addition,TiAl3 precipitates were observed in the diffusion layer.The hardness value of the mixed interface was higher than 350 HV,due to the larger amount of intermetallic compounds(IMCs).The lap shear strength reached a maximum value of 147 MPa with medium heat input and an interface that exits in a critical state between diffusive and mixed interfaces.All the specimens fractured at the interface,which was attributed to the presence of IMCs.展开更多
Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist ...Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist high-speed impact. It is concluded that different microstructures of Al-Sc and Al-Ti alloys, including different grain sizes and secondary particles precipitated in the matrix, result in their greatly different capabilities of resisting impact. Furthermore, the effect of the size range ofnanoscale A13Sc precipitate in A1-Sc alloy on the resistance of high-speed impact was investigated. In addition, computer simulations and validation of these simulations were developed which fairly accurately represented residual crater shapes/geometries. Validated computer simulations allowed representative extrapolations of impact craters well beyond the laboratory where melt and solidification occurred at the crater wall, especially for hypervelocity impact （〉5 km/s）.展开更多
The structural stability of the intermetallics AlTi3, Al2Ti, Al3Ti4 and Al3Ti in the Al-Ti system has been investigated using density functional theory （DFT） and density functional perturbation theory （DFPT）. The ...The structural stability of the intermetallics AlTi3, Al2Ti, Al3Ti4 and Al3Ti in the Al-Ti system has been investigated using density functional theory （DFT） and density functional perturbation theory （DFPT）. The calculated ground-state convex hull is in agreement with the experimental researches. Al3Ti4 （hP7） is metastable at 0 K and may be stabilized as the temperature increases due to the effects of the vibration entropy. For Al2Ti, r-Al2Ti is stable at 0 K and h-Al2Ti is stabilized by the vibration entropy at high temperatures. Al3Ti （tI16） is unstable considering vibration effects and Al3Ti （tI8） is the most stable structure at 0 K.展开更多
The Al?Ti composite oxide films with high dielectric constant were prepared by hydrolysis precipitation and anodizing. The growth, structure and electrical properties of the Al?Ti composite oxide films formed at diffe...The Al?Ti composite oxide films with high dielectric constant were prepared by hydrolysis precipitation and anodizing. The growth, structure and electrical properties of the Al?Ti composite oxide films formed at different anodizing temperatures from 25°C to 85°C have been studied by dissolution of anodic oxide films, Auger electron spectroscopy (AES), and electrical measurements. With the anodizing temperature increasing, the film growth rate increases, the structure of two layers in the Al?Ti composite oxide film converts into three layers, I–V characteristics change evidently, and the specific capacitance achieves a peak value at about 75°C. The local breakdown in the composite oxide films formed at 50°C occurs obviously, which may be contributed to the lowest leakage current and the highest withstanding voltage.展开更多
The present study focuses on interface microstructure and joint formation.AA6061 aluminum alloy(Al)and commercial pure titanium(Ti)joints were welded by ultrasonic spot welding(USW).The welding energy was 1100-3200 J....The present study focuses on interface microstructure and joint formation.AA6061 aluminum alloy(Al)and commercial pure titanium(Ti)joints were welded by ultrasonic spot welding(USW).The welding energy was 1100-3200 J.The Al-Ti joint appearance and interface microstructure were observed mainly via optical microscopy and field emission scanning electron microscopy.Results indicated that a good joint can be achieved only with proper welding energy of 2150 J.No significant intermetallic compound(IMC)was found under all conditions.The high energy barriers of Al-Ti and difficulties in diffusion were the main reasons for the absence of IMC according to kinetic analysis.The heat input is crucial for the material plastic flow and bonding area,which plays an important role in the joint formation.展开更多
Dry sliding wear behaviors of the Al 10Ti alloy prepared by mechanical alloying (MA) were investigated and compared with those of the alloy obtained by the rapid solidification (RS) process. The results show that, und...Dry sliding wear behaviors of the Al 10Ti alloy prepared by mechanical alloying (MA) were investigated and compared with those of the alloy obtained by the rapid solidification (RS) process. The results show that, under low sliding velocity of 0.66 m/s and low applied load, the predominant wear mechanism of Al 10Ti alloy against carbon steel is adhesion. The fine dispersing reinforcement in the alloy promotes the nucleation and propagation of cracks on the subsurface, leading to a higher wear rate of MA Al 10Ti alloy, compared with that of RS Al 10Ti alloy. With increasing normal load, the formation and spallation of transfer layers on the worn surface become the predominant wear mechanism. Therefore, the wear resistance of the alloy obtained by MA surpasses that achieved by RS due to the higher strength at both ambient and elevated temperature. The wear transfer layer of the MA Al 10Ti alloy is determined to be consisted mainly of Fe 2O 3 and metal Fe. [展开更多
mploying pure aluminum for address lines of TFT-LCDs has a severe problem of hillock formation at elevated temperature. However, in the case of large TFT-LCDs more than 254 mm, it is impossible to use refractory metal...mploying pure aluminum for address lines of TFT-LCDs has a severe problem of hillock formation at elevated temperature. However, in the case of large TFT-LCDs more than 254 mm, it is impossible to use refractory metals for address lines because of their high resistivity. The Al-Ti alloy films for address lines of TFT-LCDs were studied and it was found that Al-Ti alloy film has excellent resistance of Al-Ti alloy to hillocks. The effect of Ti content on properties of Al-Ti alloy film was investigated.展开更多
Titanium is an excellent grain refiner for aluminium and aluminium alloys, and the addition is normal-ly made by melt inoculation with aluminium-titanium master alloys typically containing 2.5% and 5%titaniurn. The pa...Titanium is an excellent grain refiner for aluminium and aluminium alloys, and the addition is normal-ly made by melt inoculation with aluminium-titanium master alloys typically containing 2.5% and 5%titaniurn. The paper describes a process for the production of Al-2.5% Ti and Al-5% Ti master alloys by di-rect alloying of the metals, and presents the results obtained from the heats taken under different processconditions. Alloying efficiencies as high as 96%, computed on the basis of titanium recovery. have been ob-tained in the case of 2.5% Ti master alloy as against 900/0 for the 5% Ti master alloy, al operation temperatures of 1050℃ and 1200℃ respectively. The lower efficiency in the case of higher titanium master alloy isattributed to incomplete dissolution of titanium and the significant oxidation losses occurring at the highertemperature of operation.展开更多
文摘Research and development efforts are still very active on 718-type alloys although two major members of this widely used family, 718 and 625, were invented almost a half-century ago. Emphasis in this type of work at ATI Allvac is directed at improving existing alloys and developing new alloys to meet ever-increasing industrial demands. The improvement of existing alloys is exemplified by addition of minor elements P and B in alloy 718. The discovery of the beneficial effect of P and B in wrought alloy 718 led to development of a new, modified alloy, AllvacH 718 ERR. A large effort has also been directed at studying the effects of major element modifications in 718-type alloys, and a new alloy, AllvacR 718PlusTM, has been developed. The new alloy has much better high temperature capability, especially thermal stability, approaching the level of Waspaloy but retains excellent processing characteristics, similar to alloy 718. Alloy 718PlusTM should be useful in any 718-type application requiring a higher working temperature. The properties and processing of this alloy are introduced in this paper.
基金Project (ZR2011EL023) supported by the Natural Science Foundation of Shandong Province,ChinaProject (12CX04057A) supported by the Fundamental Research Funds for the Central Universities,China
文摘Al-Ti diffusion couples were made by embedded technology and treated at the temperature between the melting points of Al and Ti. The microstructure evolution and growth mechanism of the Al-Ti DRZ were investigated. The result shows that the DRZ, the mixture of TiAl3 and Al, grows layer by layer along their chemical equilibrium zone. In the course, the growth interface moves toward the aluminum side. TiAl3 is the only new phase which forms earliest in the course of heat-treatment. The growth mechanism of the DRZ changes after the phase transition of titanium. Before the phase transition of titanium, the growth of the DRZ is controlled by the dissolution speed of the titanium to the molten aluminum, while after the phase transition of titanium, the growth is controlled by the chemical reaction speed of Al and Ti atoms, and consequently, its growth rate is greatly increased.
文摘Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.
基金financial support of the project from Shandong Provincial Natural Science Foundation, China (No. ZR2016EEM43)
文摘Friction stir welding(FSW)was performed to produce Al/Ti lap joints under various welding conditions.More heat was generated when rotational rate increased or traversing rate decreased.Two types of Al/Ti interfaces–mixed interface and diffusive interface–were formed under different welding conditions.The diffusive interface was formed with low heat input,and the mixed interface was formed more heat.The grains at the mixed interface were larger than those at the diffusive interface because of the higher heat input.Moreover,the microstructure of the mixed interface had a lower texture intensity compared with that of the diffusive interface,which was attributed to the enhanced continuous dynamic recrystallization(CDRX).TiAl3 was formed at the diffusive interface.When the interface varied to the mixed interface as heat input increased,TiAl was fomed within the Al/Ti mixture following the formation of TiAl3.In addition,TiAl3 precipitates were observed in the diffusion layer.The hardness value of the mixed interface was higher than 350 HV,due to the larger amount of intermetallic compounds(IMCs).The lap shear strength reached a maximum value of 147 MPa with medium heat input and an interface that exits in a critical state between diffusive and mixed interfaces.All the specimens fractured at the interface,which was attributed to the presence of IMCs.
文摘Al-Sc and Al-Ti semi-infinite targets were impacted by high-speed projectiles at velocities of 0.8, 1.0, 1.2 and 1.5 km/s, respectively. It is found that the Al-Sc targets demonstrate more excellent ability to resist high-speed impact. It is concluded that different microstructures of Al-Sc and Al-Ti alloys, including different grain sizes and secondary particles precipitated in the matrix, result in their greatly different capabilities of resisting impact. Furthermore, the effect of the size range ofnanoscale A13Sc precipitate in A1-Sc alloy on the resistance of high-speed impact was investigated. In addition, computer simulations and validation of these simulations were developed which fairly accurately represented residual crater shapes/geometries. Validated computer simulations allowed representative extrapolations of impact craters well beyond the laboratory where melt and solidification occurred at the crater wall, especially for hypervelocity impact （〉5 km/s）.
基金supported by the National Basic Research Program of China (No.2006CB605103)the National Natural Science Foundation of China (No.50971119)
文摘The structural stability of the intermetallics AlTi3, Al2Ti, Al3Ti4 and Al3Ti in the Al-Ti system has been investigated using density functional theory （DFT） and density functional perturbation theory （DFPT）. The calculated ground-state convex hull is in agreement with the experimental researches. Al3Ti4 （hP7） is metastable at 0 K and may be stabilized as the temperature increases due to the effects of the vibration entropy. For Al2Ti, r-Al2Ti is stable at 0 K and h-Al2Ti is stabilized by the vibration entropy at high temperatures. Al3Ti （tI16） is unstable considering vibration effects and Al3Ti （tI8） is the most stable structure at 0 K.
基金This work was supported by the Science and Technology Foundation of UESTC of Young Scholars(Grant No.L0801301JX04018).
文摘The Al?Ti composite oxide films with high dielectric constant were prepared by hydrolysis precipitation and anodizing. The growth, structure and electrical properties of the Al?Ti composite oxide films formed at different anodizing temperatures from 25°C to 85°C have been studied by dissolution of anodic oxide films, Auger electron spectroscopy (AES), and electrical measurements. With the anodizing temperature increasing, the film growth rate increases, the structure of two layers in the Al?Ti composite oxide film converts into three layers, I–V characteristics change evidently, and the specific capacitance achieves a peak value at about 75°C. The local breakdown in the composite oxide films formed at 50°C occurs obviously, which may be contributed to the lowest leakage current and the highest withstanding voltage.
基金We are grateful for the financial support provided by the National Natural Science Foundation of China(Nos.51974100 and 51605117).
文摘The present study focuses on interface microstructure and joint formation.AA6061 aluminum alloy(Al)and commercial pure titanium(Ti)joints were welded by ultrasonic spot welding(USW).The welding energy was 1100-3200 J.The Al-Ti joint appearance and interface microstructure were observed mainly via optical microscopy and field emission scanning electron microscopy.Results indicated that a good joint can be achieved only with proper welding energy of 2150 J.No significant intermetallic compound(IMC)was found under all conditions.The high energy barriers of Al-Ti and difficulties in diffusion were the main reasons for the absence of IMC according to kinetic analysis.The heat input is crucial for the material plastic flow and bonding area,which plays an important role in the joint formation.
文摘Dry sliding wear behaviors of the Al 10Ti alloy prepared by mechanical alloying (MA) were investigated and compared with those of the alloy obtained by the rapid solidification (RS) process. The results show that, under low sliding velocity of 0.66 m/s and low applied load, the predominant wear mechanism of Al 10Ti alloy against carbon steel is adhesion. The fine dispersing reinforcement in the alloy promotes the nucleation and propagation of cracks on the subsurface, leading to a higher wear rate of MA Al 10Ti alloy, compared with that of RS Al 10Ti alloy. With increasing normal load, the formation and spallation of transfer layers on the worn surface become the predominant wear mechanism. Therefore, the wear resistance of the alloy obtained by MA surpasses that achieved by RS due to the higher strength at both ambient and elevated temperature. The wear transfer layer of the MA Al 10Ti alloy is determined to be consisted mainly of Fe 2O 3 and metal Fe. [
文摘mploying pure aluminum for address lines of TFT-LCDs has a severe problem of hillock formation at elevated temperature. However, in the case of large TFT-LCDs more than 254 mm, it is impossible to use refractory metals for address lines because of their high resistivity. The Al-Ti alloy films for address lines of TFT-LCDs were studied and it was found that Al-Ti alloy film has excellent resistance of Al-Ti alloy to hillocks. The effect of Ti content on properties of Al-Ti alloy film was investigated.
文摘Titanium is an excellent grain refiner for aluminium and aluminium alloys, and the addition is normal-ly made by melt inoculation with aluminium-titanium master alloys typically containing 2.5% and 5%titaniurn. The paper describes a process for the production of Al-2.5% Ti and Al-5% Ti master alloys by di-rect alloying of the metals, and presents the results obtained from the heats taken under different processconditions. Alloying efficiencies as high as 96%, computed on the basis of titanium recovery. have been ob-tained in the case of 2.5% Ti master alloy as against 900/0 for the 5% Ti master alloy, al operation temperatures of 1050℃ and 1200℃ respectively. The lower efficiency in the case of higher titanium master alloy isattributed to incomplete dissolution of titanium and the significant oxidation losses occurring at the highertemperature of operation.
