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1.
The influence of Zirconium on the grain refinement performance of Al–Ti–C master alloys and the effect mechanism has been
studied in this paper. The experimental results show that Zr not only results in poisoning the Al–Ti–B master alloy, but also
poisons the Al–Ti–C master alloys. The poisoning effect is more obvious at higher melting temperature. When 0.12%Zr is added
into the melt, the grain refinement performance of Al–5Ti–0.4C refiner with 0.2% addition level absolutely disappears at 800 °C.
The experimental results also show that it is difficult to refine the commercial purity Al containing 0.15%Zr by Al–5Ti–0.4C
master alloy. Further experiments show that the Zr element can interact with both TiAl3 and TiC phases. If both of them are present, Zr preferentially reacts with TiAl3 phase. 相似文献
2.
The microstructures and dry sliding wear behavior of Al–7Si and Al–7Si–2.5Cu cast alloys were studied after various melt treatments
like grain refinement and modification. Results indicate that combined grain refined and modified Al–7Si–2.5Cu cast alloys
have microstructures consisting of uniformly distributed α-Al grains, eutectic Al– silicon and fine CuAl2 particles in the interdendritic region. These alloys exhibited better wear resistance in the cast condition compared with
the same alloy subjected to only grain refinement or modification. The improved wear resistances of Al–7Si–2.5Cu cast alloys
are related to the refinement of the aluminum grain size, uniform distribution of eutectic Al-silicon and fine CuAl2 particles in the interdendritic region resulting from combined refinement and modification. This paper attempts to investigate
the influence of the microstructural changes in the Al–7Si and Al–7Si–2.5Cu cast alloys by grain refinement, modification
and combined action of both on the sliding wear behavior. 相似文献
3.
Yucel Birol 《Journal of Materials Science》2007,42(13):5123-5128
Al–TiCp composites have been extensively studied in recent years not only because of their attributes as wear-resistant structural
materials but also on account of their potential as very efficient grain refiners. Al–Ti–C alloys of various compositions
have already been commercialized as grain refining master alloys and have long been in use in aluminium foundries world wide.
The present work was undertaken to investigate the possibility of manufacturing Al–TiCp grain refiner master alloy tablets by the mechanical alloying route. Carbon was mechanically alloyed into Al–Ti alloy powder
grains via high energy ball milling. The Al–Ti/C powder blend thus obtained was heat treated to promote the precipitation
of TiC. Al4C3 was the first phase to form inside the powder grains upon thermal exposure. The Al4C3 particles which were too small to be identified with the optical microscope until 750 °C, have grown until 850 °C where they
have started to react with Al3Ti to produce TiC. A very fine dispersion of TiC particles was thus generated inside the powder particles while the Al3Ti phase has almost vanished. 相似文献
4.
The structural examinations and tensile properties of thin-section Al castings (319 Al alloy) have been investigated by applying a pattern with different cross sections (2–12 mm). Al–5Ti–1B and Al–5Zr grain refiners were added to the molten Al alloy to produce different levels of Ti (0.01%, 0.05%, 0.1% and 0.15%) and Zr (0.05%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5%) in the castings. From macrostructural studies, it was found that Al–5Zr is less effective in grain refining of 319 alloy in comparison with Al–5Ti–1B master alloy. The optimum levels of grain refiners were selected for determination of tensile properties. T6 heat treatment was applied for selected specimens before tensile testing. Further structural results also showed that thinner sections are less affected by grain refiners. This observation was found to be in a good agreement with tensile test results, where tensile properties of the base and grain refined alloys did not show considerable differences in thinner sections (<6 mm). 相似文献
5.
The microstructures, machinability and surface characteristics of Al–7Si and Al–7Si–2.5Cu cast alloys were studied after various
melt treatments like grain refinement and modification. Results indicate that combined grain refined and modified Al–7Si–2.5Cu
cast alloys have microstructures consisting of uniformly distributed α-Al grains, eutectic Al–silicon and fine CuAl2 particles in the interdendritic region. These alloys exhibited better machinability and surface characteristics in the cast
condition compared with the same alloy subjected to only grain refinement or modification. Performances of the turning inserts
(Un-coated, PVD and Polished CVD diamond coated) were evaluated in machining Al–7Si and Al–7Si–2.5Cu cast alloys under dry
environment using a lathe. The Polished CVD diamond coated insert outperformed the Un-coated or PVD-coated cutting inserts
which suffered from sizeable edge buildup leading to higher cutting force and poor surface finish. The Polished CVD diamond
coated insert shows a very small steady wear without flaking of the diamond film during cutting. This paper attempts to investigate
the influence of grain refinement, modification and combined action of both on the microstrutural changes in the Al–7Si and
Al–7Si–2.5Cu cast alloys and their machinability and surface finish when different turning inserts used. 相似文献
6.
This study was undertaken to investigate the influence of Al–5Ti–1B and Al–5Zr master alloys on the structural characteristics and tensile properties of Al–12Zn–3 Mg–2.5Cu aluminum alloy. The optimum amount for Ti and Zr containing master alloys was selected as 1 wt.% and 6 wt.%, respectively. The results also showed that Ti containing master alloy is more effective in reducing average grain size of the alloy. T6 heat treatment was applied for all specimens before tensile testing. In heat treated condition, the average tensile strength of 505 MPa was found to be increased to 621 MPa for sample refined with 1 wt.% Al–5Ti–1B (0.05 wt.% Ti). SEM fractography of the fractured faces of several castings showed an overall macroscopically brittle appearance at low magnifications. At higher magnifications, unrefined specimens showed cracking along the grains, whereas Ti-refined specimens showed cracks in individual intermetallic compounds. 相似文献
7.
In the present investigation, the microstructural and mechanical properties study of A356 alloy have been discussed. The microstructural
aspect of cast A356 alloy employed in the present study is strongly dependent on the grain refinement (Ti and B) and modification
(Sr). The mechanical properties such as PS, UTS, %E, %R, YM and VHN have been investigated. This paper deals with the combined
effect of grain refinement and modification, which improves the overall mechanical properties of the alloy. It is also a well-known
fact that the mechanical properties of cast A356 alloy were improved by subjecting suitable melt treatment such as grain refinement,
modification and mould vibration, etc. The quality of castings and their properties can be achieved by refining of α-Al dendrites
in A356 alloy by means of the addition of elements such as Ti and B which reduces the size of α-Al dendrites, which otherwise
solidifies with coarse columnar α-Al dendritic structure. In addition, modification is normally adopted to achieve improved
mechanical properties. Metallographic studies reveal that the structure changes from coarse columnar dendrites to fine equiaxed
ones on the addition of grain refiner and further, plate like eutectic silicon to fine particles on addition of 0.20% of Al–10Sr
modifier. The present result shows that a reduction in the size of α-Al dendrites, modification of eutectic Si and improvement
in the mechanical properties were observed with the addition of grain refiner Al–3Ti, Al–3B and modifier Al–10Sr either individual
addition or in combination. The change in the microstructure from coarse columnar α-Al dendrites to fine equiaxed dendrites
and plate like eutectic silicon to rounded particles leads to improved mechanical properties. 相似文献
8.
The effect of TiAl3 particle size and distribution on their settling and dissolution behaviour in molten aluminium during grain refinement has
been studied. For this purpose Al–5Ti master alloys containing blocky TiAl3 particles of different size and distribution are synthesised at reaction temperatures 750, 800 and 850 °C for 60 min and
used for grain refinement. The extent of fading and the recovery due to stirring is calculated from the measured grain size
and used to judge the dissolution and settling behaviour of TiAl3 in molten Al, which is greatly attributed to its size and distribution in Al–5Ti master alloy. Fine TiAl3 particle dissolve faster in the melt and cause fading. Larger size TiAl3 particles exist for longer time in molten Al and act as a nucleating site even when added in hypoperitectic concentration
(0.05 wt% Ti). 相似文献
9.
It is very difficult to simultaneously refine and modify Si particles in hypereutectic Al–Si–Cu alloys to enhance their ductility.
This study investigates how nanoparticles affect Si particles during solidification in hypereutectic Al–Si–Cu alloys. 0.5
wt% γ-Al2O3 nanoparticles were added in hypereutectic Al–20Si–4.5Cu alloy melt and further dispersed through an ultrasonic-cavitation-based
technique. The as-cast Al–20Si–4.5Cu–Al2O3 nanocomposites showed marked enhancements in both ductility and strength. The ductility of Al2O3 nanocomposite was more than two times higher than that of the monolithic alloy without the nanoparticles. Microstructural
analysis with optical and scanning electron microscopy revealed that both the primary and eutectic Si particles were significantly
refined. The primary Si particles were refined from star shapes to polygon or blocky shapes, and their edges and corners were
much smoother. The large plate eutectic Si particles were also modified into the fine coralline-like ones. The porosity of
alloy was also reduced with the addition of γ-Al2O3 nanoparticles. Study suggests that γ-Al2O3 nanoparticles simultaneously refine and modify Si particles as well as reduce porosity in cast Al–20Si–4.5Cu, resulting in
unusual ductility enhancement that could have great potential for numerous applications. 相似文献
10.
Mingbo Yang Fusheng Pan Renju Cheng Aitao Tang 《Journal of Materials Science》2007,42(24):10074-10079
In the article, the effects of Al–10Sr and Mg–10Sr master alloys on the grain refinement of AZ31 magnesium alloy, are compared
and analyzed. The results indicate that adding Al–10Sr or Mg–10Sr master alloys to AZ31 magnesium alloy could effectively
reduce its grain size, but the refinement efficiency of Mg–10Sr master alloys is higher than that of the Al–10Sr master alloys.
In addition, for a given melt holding time, the refinement efficiency of the two master alloys respectively increase with
Sr adding amount increasing from 0 to 0.1 wt%, and the increasing laws are similar. For a given Sr adding amount, the refinement
efficiency of Al–10Sr mater alloy gradually increases with the melt holding time increasing from 20 to 80 min, but its changing
is not obvious for the Mg–10Sr mater alloy. The difference of refinement efficiency for the Al–10Sr and Mg–10Sr master alloys
might be related to the dissolution modes and rates of Al4Sr and Mg17Sr2 phases in the melt of AZ31 magnesium alloy. 相似文献
11.
Zhongwei CHEN Zhi HE Wanqi JIE 《材料科学技术学报》2007,23(5):619-622
Based on the assumption that the nucleation substrates are activated by constitutional undercooling generated by an adjacent grain growth and solute distribution during the initial solidification, a model for calculation of the grain size of aluminum alloys with the grain refinement is developed, where the nucleation is dominated by two parameters, i.e. growth restriction factor Q and the undercooling parameter P. The growth restriction factor Q is proportional to the initial rate of constitutional undercooling development and can be used directly as a criterion of the grain refinement in the alloys with strong potential nucleation particles. The undercooling parameter P can be regarded as the maximum of constitutional undercooling △Tc. For weak potential nucleation particles, the use of RGS would be more accurate. The experimental data of the grain refinement of pure aluminum and AlSi7 alloys are coincident predicted results with the model. 相似文献
12.
A. M. Nabawy A. M. Samuel F. H. Samuel H. W. Doty 《Journal of Materials Science》2012,47(9):4146-4158
This study was undertaken to investigate the effects of chemical composition and mold temperature (MT) on the hot-tearing
susceptibility (HTS) of an experimental Al–2% Cu–1% Si alloy using a constrained rod casting mold. The HTS results were then
compared with 206 (Al–5 wt% Cu) alloys containing the same additions. In general, the Al–2% Cu–1% Si based alloys exhibited
higher resistance to hot-tearing than did the 206-based alloys. It was found that an elevated MT is beneficial in reducing
the HTS of the Al–2% Cu–1% Si and 206 alloys in that the HTS value decreased from over 21 to less than 5, as the MT was increased
from 250 to 450 °C. Increasing the Si content reduced the HTS of the Al–2% Cu–1% Si alloy considerably; this reduction may
be attributed to an increase in the volume fraction of eutectic in the structure. The addition of Sr caused deterioration
in the hot-tearing resistance of the base alloy due to the formation of Sr-oxides and an extension of the freezing range of
the alloy. The refinement of the grain structure obtained with the Zr–Ti–B addition decreased the severity of hot-tearing
as a result of an increase in the number of intergranular liquid films per unit volume and a delay in reaching the coherency
point. It was also observed that α-Fe intermetallic particles may impede the propagation of hot-tearing cracks. The Al–2% Cu–1% Si alloy with 1 wt% Si addition
was judged to be the best composition in view of its low HTS. 相似文献
13.
Pennekamp PH Wimmer MA Eschbach L Burian B Koch P Kraft CN 《Journal of materials science. Materials in medicine》2007,18(10):2053-2060
Beta-titanium alloys such as Ti–15Mo are increasingly utilized for orthopaedic implant applications because of their excellent
corrosion resistance and low elastic modulus. Particularly in osteosynthesis, where the biomaterial stands in direct contact
to soft tissue, undesirable biologic reactions may have severe consequences especially in the vulnerable state of trauma and
added iatrogenic damage to the microvascular system. In a comparative study we therefore assessed in vivo nutritive perfusion
and leukocytic response of striated muscle to the biomaterials Ti–15Mo, Ti–6Al–4V and Ti–6Al–7Nb, thereby drawing conclusions
on their short term inflammatory potential. Utilizing the well established skinfold chamber preparation in the hamster and
intravital fluorescence microscopy, we could not demonstrate any significant discrepancies between the three alloys. All metals
induced an initial moderate inflammatory response in skeletal muscle microcirculation. While recuperation of animals treated
with Ti–15Mo and Ti–6Al–7Nb was prompt, we documented a slightly more sluggish recovery of Ti–6Al–4V treated animals. A gross
toxicity was not observed for any of the alloys. Conclusively, Ti–15Mo, Ti–6Al–4V and Ti–6Al–7Nb induce an only transient
inflammatory answer of the striated muscle microvascular system. Our results indicate that on the microvascular level the
tested bulk Ti-alloys do not cause enduring biologic impairment in muscle.
No benefit of any kind has or will be received either directly or indirectly by the authors. 相似文献
14.
Kim TN Balakrishnan A Lee BC Kim WS Dvorankova B Smetana K Park JK Panigrahi BB 《Journal of materials science. Materials in medicine》2008,19(2):553-557
The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained titanium [produced by a severe
plastic deformation (SPD) process] has been studied in this work. SPD Ti showed much higher strength than the coarse grained
Ti and equivalent to that of Ti–6Al–4V alloy. Better cell proliferation was observed on SPD Ti compared to conventional Ti
and Ti–6Al–4V alloy. This could be attributed to the increased surface free energy by reduction in the grain size and possibly
the presence of a large number of nano size grooves at the triple point junctions in SPD Ti sample. There was no significant
difference in the results of cytotoxicity tests of fine and coarse grained materials. 相似文献
15.
A melt encasement (fluxing) technique has been used to systematically study the velocity-undercooling relationship in samples of Cu and Cu-O and Cu-3 wt% Sn at undercoolings up to 250 K. In pure Cu the solidification velocity increased smoothly with undercooling up to a maximum of 97 m s-1. No evidence of grain refinement was found in any of the as-solidified samples. However, in Cu doped with >200 ppm O we found that samples undercooled by more than 190 K had a grain refined microstructure and that this corresponded with a clear discontinuity in the velocity-undercooling curve. Microstructural evidence in these samples is indicative of dendritic fragmentation having occurred. In Cu-Sn grain refinement was observed at the highest undercoolings (greater than 190 K in Cu-3 wt% Sn) but without the spherical substructure seen to accompany grain refinement in Cu-O alloys. Microstructural analysis using light microscopy, texture analysis and microhardness measurements reveals that recrystallisation accompanies the grain refinement at high undercoolings. Furthermore, at undercoolings between 110 K and 190 K, a high density of subgrains are seen within the microstructure which indicate the occurrence of recovery, a phenomenon previously unreported in samples solidified from highly undercooled melts. 相似文献
16.
The deformation behavior of spray-formed hypereutectic aluminum–silicon alloys—AlSix (x = 18, 25, and 35 wt%)—has been studied by means of compression test at various temperatures and strain rates. The flow stress
of the spray-formed Al–Si alloys increases with decreasing compression temperature and increasing strain rate. Higher silicon
content in the alloys also leads to higher flow stress during deformation. The flow curves determined from the compression
tests exhibit that the deformation of the materials is controlled by two competing mechanisms: strain hardening, and flow
softening. Particle damage during the deformation may have an influence on the flow curves of the alloys with large silicon
particles. Based on the flow curves obtained from the compression tests and knowledge of aluminum extrusion, the spray-formed
hypereutectic Al–Si alloy billets have been hot extruded into wires with a high area reduction ratio around 189. Since primary
silicon particles were greatly refined and uniformly distributed in the spray-formed materials, the heavy deformations of
the spray-formed Al–Si alloys containing high amount of silicon were successfully performed. 相似文献
17.
Shengyin Zhou Rui Hu Li Jiang Jinshan Li Hongchao Kou Hui Chang Lian Zhou 《Journal of Materials Science》2011,46(16):5495-5502
High undercooling has been achieved in Co80Pd20 melts by employing the method of molten glass denucleating combined with cyclic superheating, and the microstructure evolution
with undercooling was systematically investigated. Within the achieved range of undercooling, 0–415 K, two kinds of grain
refinements have been observed in the solidification microstructures. The three critical undercoolings are 72, 95, and 142 K,
respectively. When undercooling is less than 72 K, the coarse dendritic morphology is formed, which is similar to the conventional
as-cast microstructure. The first grain refinement occured in the range of undercooling, 72–95 K can be attributed to the
breakup of dendrite-skeleton owing to remelting. When undercooling locates within 95–142 K, highly developed directional fine
dendrite can be obtained because the severe solute trapping weakens the effect of solute diffusion during the dendrite growth.
The second grain refinement occurred when undercooling exceeds the critical undercooling (∆T* = 142 K), the formation of fined equiaxed microstructure can be ascribed to the stress that originates from the extremely
rapid solidification process, which resulted in the dendrite fragmentation finally. 相似文献
18.
Mariusz Andrzejczuk Małgorzata Lewandowska Jerzy Latuch Krzysztof Jan Kurzydłowski 《Journal of Materials Science》2011,46(16):5454-5459
Properties of engineering metallic alloys (e.g., fracture toughness, corrosion resistance) are often limited by the presence
of primary intermetallic particles which form during conventional solidification. Rapid solidification brings about much more
homogenous amorphous and/or nanocrystalline structure with reduced density of primary particles. Rapidly solidified thin ribbons
obtained by melt spinning are usually considered as intrinsically homogenous. However, due to different cooling conditions
at the wheel surface and on the side exposed to the ambient environment, structure of such ribbons may vary significantly
across its thickness. The materials studied in this study were 30–40 μm thickness ribbons of nanocrystalline hyper- and hypo-eutectic
Al–Si–Zr alloys produced by melt-spinning method. Transmission electron microscopy and high resolution scanning transmission
electron microscopy were used to characterize the structure homogeneity across the ribbons. Thin foils for transmission observations
were prepared by focused ion beam system. Microstructural observations confirmed nanocrystalline character of Al–Si–Zr alloys.
However, these observations revealed inhomogeneity of the structure across the ribbon width. 相似文献
19.
V. C. Srivastava G. B. Rudrakshi V. Uhlenwinkel S. N. Ojha 《Journal of Materials Science》2009,44(9):2288-2299
In the present investigation, different Al based alloys such as Al–Si–Pb, Al–Si, Al–Si–Fe and 2014Al + SiC composites have
been produced by spray forming process. The microstructural features of monolithic alloys and composite materials have been
examined and their wear characteristics have been evaluated at different loads and sliding velocities. The microstructural
features invariably showed a significant refinement of the primary phases and also modification of secondary phases in Al-alloys.
The Pb particles in Al–Si–Pb alloy were observed to be uniformly distributed in the matrix phase besides decorating the grain
boundaries. The spray formed composites showed uniform distribution of SiC particles in the matrix. It was observed that wear
resistance of Al–Si alloy increases with increase in Pb content; however, there is not much improvement after addition of
Pb more than 20%. The coefficient of friction reduced to 0.2 for the alloy containing 20%Pb. A sliding velocity of 1 ms−1 was observed to be optimum for high wear resistance of these materials. Alloying elements such as Fe and Cu in Al–Si alloy
lead to improved wear resistance compared to that of the base alloy. The addition of SiC in 2014Al alloy gave rise to considerable
improvement in wear resistance but primarily in the low pressure regime. The wear rate seemed to decrease with increase in
sliding velocity. The wear response of the materials has been discussed in light of their microstructural features and topographical
observation of worn surfaces. 相似文献
20.
Yu Xiang Ni Bo Feng Jianxin Wang Xiong Lu Shuxin Qu Jie Weng 《Journal of Materials Science》2009,44(15):4031-4039
Titanium and its alloys have been applied in orthopedics due to their biocompatibility, mechanical, and physical properties.
Here we use decyl bis phosphonate (DBP) and collagen I to modify Ti–6Al–4V through layer-by-layer technique in order to improve
its bioactivity. The abilities of bovine serum albumin (BSA) adsorption and biomimetic mineralization of different sample
surfaces were studied. X-ray photoelectron spectroscopy (XPS) and water contact angle data showed that DBP and collagen I
were assembled on substrates successfully. The absorbance of BSA solution acquired from ultraviolet spectrophotometer (UV)
indicated that samples of Ti–6Al–4V/DBP/Collagen and Ti–6Al–4V/DBP/Collagen/DBP adsorbed BSA most, followed by Ti–6Al–4V/DBP
and Ti–6Al–4V. Scanning electron microscope (SEM) photos and X-ray diffraction (XRD) data showed that sample of Ti–6Al–4V/DBP/Collagen
had better bioactivity in inducing HA formation than other samples tested in this investigation. 相似文献