AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys wer...AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys were studied by XRD,OM and microhardness testing techniques.The results show that when the addition level of Al5Ti1B master alloy is less than 0.5%(mass fraction),the average grain size of the alloys decreases with the increase of Al5Ti1B content at the same holding time.But the grain size increases somewhat with further addition of Al5Ti1B.The average grain size of the alloys decreases with the increase of the holding time as it is less than 30 min at the same addition level of Al5Ti1B.It is considered that TiB2 particles can serve as the heterogeneous nucleation sites ofα-Mg during solidification,and heterogeneous nucleation is the main reason for the grain refinement of AZ61 alloys.The microhardness of the refined AZ61 alloys with 1.0%Al5Ti1B addition is increased by about 8%.展开更多
Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master...Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.展开更多
Grain refinement can offer significant benefits to both continuous casting and cast to shape products, and Al5Ti1B master alloy containing mainly TiAl 3 and TiB 2 particles in Al matrix has been proven to perform well...Grain refinement can offer significant benefits to both continuous casting and cast to shape products, and Al5Ti1B master alloy containing mainly TiAl 3 and TiB 2 particles in Al matrix has been proven to perform well for giving the best refinement, but the working method of adding Al5Ti1B rod to the furnace during casting are often related to solid deformation, and melt vibration may help to reduce the size of TiAl 3 and improve the distribution of TiB 2. Therefore the effects of solid deformation and melt vibration on the structures and refinement performance of Al5Ti1B master alloys were studied. The experimental results show that both solid deformation and melt vibration can improve the distribution of TiB 2 in Al5Ti1B master alloys, increase the interface energy and nucleation activity of TiB 2 particles. In the meantime, solid deformation can store deformation energy and melt vibration can break fragile plate like TiAl 3 compounds. So both methods can improve the refinement effectiveness of Al5Ti1B master alloys.展开更多
The mechanical properties of castings depend on the grain size.There is evidence that titanium and boron(Al-5Ti-1B master alloy)affect the grain size of magnesium alloys.Here,the influence of the addition of 0-1 wt.%o...The mechanical properties of castings depend on the grain size.There is evidence that titanium and boron(Al-5Ti-1B master alloy)affect the grain size of magnesium alloys.Here,the influence of the addition of 0-1 wt.%of Al-5Ti-1B master alloy on the grain size of AZ91 magnesium alloy was investigated.Melting of the alloy was performed in steel and corundum crucibles.To study the effect of cooling rate on grain size,cylindrical samples were cast in steel and fireclay molds.The Al-5Ti-1B master alloy addition did not change the phase composition of the AZ91 alloy.This study demonstrates that the addition of Al-5Ti-1B did not contribute to the grain refinement of the AZ91 alloy,but rather led to its coarsening for samples cast in both the steel and fireclay molds.Increasing the holding time after the addition of the Al-5Ti-1B master alloy from 15 to 110 minutes also did not lead to significant grain coarsening.The mechanical properties of the AZ91 alloy samples slightly improved after Al-5Ti-1B addition.展开更多
A near eutectic Al−12.6Si alloy was developed with 0.0wt%,2.0wt%,4.0wt%,and 6.0wt%Al−5Ti−1B master alloy.The micro-structural morphology,hardness,tensile strength,elongation,and fracture behaviour of the alloys were s...A near eutectic Al−12.6Si alloy was developed with 0.0wt%,2.0wt%,4.0wt%,and 6.0wt%Al−5Ti−1B master alloy.The micro-structural morphology,hardness,tensile strength,elongation,and fracture behaviour of the alloys were studied.The unmodified Al−12.6Si al-loy has an irregular needle and plate-like eutectic silicon(ESi)and coarse polygonal primary silicon(PSi)particles in the matrix-likeα-Al phase.The P_(Si),E_(Si),andα-Al morphology and volume fraction were changed due to the addition of the Al−5Ti−1B master alloy.The hardness,UTS,and elongation improved due to the microstructural modification.Nano-sized in-situ Al3Ti particles and ex-situ TiB_(2)particles caused the mi-crostructural modification.The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time.The Al−5Ti−1B modified alloys have a more ductile mode of fracture and more dimples compared to the unmodified alloy.展开更多
In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechani...In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechanical and structural characteristics of commercially pure aluminium are examined.Results show that increasing the melt temperature as well as employing a gating system with higher heat transfer rate increases the ultimate tensile strength(UTS)of the pure aluminium by 7%.Also,the introduction of 2wt%Al–5Ti–1B grain refiner in bar form into the overheated melt enhances the UTS values by two times,while incorporating 2wt%Al–5Ti–1B grain refiner in micro-powder form leads to achieving 32%higher UTS compared to the samples with grain refiner in the bar form due to the elimination of Al3Ti brittle phase,as confirmed by XRD patterns and SEM fracture surface images.展开更多
基金Project(2010RFQXG117)supported by the Special Fund for Technological Innovation Program of Harbin,China
文摘AZ61 alloys with different levels of Al5Ti1B master alloy additions were prepared by conventional casting method.The effects of Al5Ti1B contents and holding time on microstructures and microhardness of AZ61 alloys were studied by XRD,OM and microhardness testing techniques.The results show that when the addition level of Al5Ti1B master alloy is less than 0.5%(mass fraction),the average grain size of the alloys decreases with the increase of Al5Ti1B content at the same holding time.But the grain size increases somewhat with further addition of Al5Ti1B.The average grain size of the alloys decreases with the increase of the holding time as it is less than 30 min at the same addition level of Al5Ti1B.It is considered that TiB2 particles can serve as the heterogeneous nucleation sites ofα-Mg during solidification,and heterogeneous nucleation is the main reason for the grain refinement of AZ61 alloys.The microhardness of the refined AZ61 alloys with 1.0%Al5Ti1B addition is increased by about 8%.
文摘Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.
文摘Grain refinement can offer significant benefits to both continuous casting and cast to shape products, and Al5Ti1B master alloy containing mainly TiAl 3 and TiB 2 particles in Al matrix has been proven to perform well for giving the best refinement, but the working method of adding Al5Ti1B rod to the furnace during casting are often related to solid deformation, and melt vibration may help to reduce the size of TiAl 3 and improve the distribution of TiB 2. Therefore the effects of solid deformation and melt vibration on the structures and refinement performance of Al5Ti1B master alloys were studied. The experimental results show that both solid deformation and melt vibration can improve the distribution of TiB 2 in Al5Ti1B master alloys, increase the interface energy and nucleation activity of TiB 2 particles. In the meantime, solid deformation can store deformation energy and melt vibration can break fragile plate like TiAl 3 compounds. So both methods can improve the refinement effectiveness of Al5Ti1B master alloys.
文摘The mechanical properties of castings depend on the grain size.There is evidence that titanium and boron(Al-5Ti-1B master alloy)affect the grain size of magnesium alloys.Here,the influence of the addition of 0-1 wt.%of Al-5Ti-1B master alloy on the grain size of AZ91 magnesium alloy was investigated.Melting of the alloy was performed in steel and corundum crucibles.To study the effect of cooling rate on grain size,cylindrical samples were cast in steel and fireclay molds.The Al-5Ti-1B master alloy addition did not change the phase composition of the AZ91 alloy.This study demonstrates that the addition of Al-5Ti-1B did not contribute to the grain refinement of the AZ91 alloy,but rather led to its coarsening for samples cast in both the steel and fireclay molds.Increasing the holding time after the addition of the Al-5Ti-1B master alloy from 15 to 110 minutes also did not lead to significant grain coarsening.The mechanical properties of the AZ91 alloy samples slightly improved after Al-5Ti-1B addition.
基金The authors would also like to thank NIT,Durgapur RIG#2 project for financial support and the Director of National In-stitute of Technology Durgapur,India,for his continuous en-couragement.
文摘A near eutectic Al−12.6Si alloy was developed with 0.0wt%,2.0wt%,4.0wt%,and 6.0wt%Al−5Ti−1B master alloy.The micro-structural morphology,hardness,tensile strength,elongation,and fracture behaviour of the alloys were studied.The unmodified Al−12.6Si al-loy has an irregular needle and plate-like eutectic silicon(ESi)and coarse polygonal primary silicon(PSi)particles in the matrix-likeα-Al phase.The P_(Si),E_(Si),andα-Al morphology and volume fraction were changed due to the addition of the Al−5Ti−1B master alloy.The hardness,UTS,and elongation improved due to the microstructural modification.Nano-sized in-situ Al3Ti particles and ex-situ TiB_(2)particles caused the mi-crostructural modification.The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time.The Al−5Ti−1B modified alloys have a more ductile mode of fracture and more dimples compared to the unmodified alloy.
文摘In current research,the interactive effects of different parameters such as melt overheating temperature,the location of gating system and incorporation of the grain refiner in bar and micro-powder form on the mechanical and structural characteristics of commercially pure aluminium are examined.Results show that increasing the melt temperature as well as employing a gating system with higher heat transfer rate increases the ultimate tensile strength(UTS)of the pure aluminium by 7%.Also,the introduction of 2wt%Al–5Ti–1B grain refiner in bar form into the overheated melt enhances the UTS values by two times,while incorporating 2wt%Al–5Ti–1B grain refiner in micro-powder form leads to achieving 32%higher UTS compared to the samples with grain refiner in the bar form due to the elimination of Al3Ti brittle phase,as confirmed by XRD patterns and SEM fracture surface images.
