Al-Ti-B和Al-5%Sr中间合金对轮毂铝合金的晶粒细化和变质作用

采用不同处理状态的Al Ti B中间合金和Al 5 %Sr中间合金 ,对轮毂铝合金Al 7%Si 0 35 %Mg进行晶粒细化和变质处理。在Instron 85 0 2 - 3411型液压伺服疲劳试验机上测试被处理合金的抗拉强度和伸长率。结果表明 :Al Ti B中间合金可有效地细化Al 7%Si 0 35 %Mg合金 ,加入 0 0 6 %Ti即可使合金获得良好的细化效果 ;Al 5 %Sr中间合金可有效地对Al 7%Si 0 35 %Mg合金进行变质 ,加入 0 0 2 %Sr即可使合金获得良好的变质效果 ;快速凝固和热变形处理可有效地改善Al Ti B的晶粒细化效果和Al 5 %Sr的变质效果 ,在获得相同的晶粒细化和变质程度的情况下 ,使Al Ti B和Al 5 %Sr中间合金的加入量减少约 5 0 % ,并使Al 7%Si 0 35 %Mg合金的力学性能有所提高     

Effect of Si content on surface hardening of Al–Si alloy by shot peening treatment

The effect of Si content was investigated for Al–Si alloys (Al-7%, 11%, 18%Si) by shot peening process. The hardness increment by shot peening increased as the Si contents in Al–Si alloys increased. Finer Si particles and more dense distribution of those were observed in Al–18%Si than Al–7%Si. As Si contents of Al–Si alloys increased, grain size at the surface area of Al–Si alloy decreased. Higher hardness of Al–Si alloy with higher Si content could be attributable to more dense and refine Si particles and accelerated grain refinement during severe deformation.     

微量元素对快冷高硅铝合金粉末特性的影响

制备了含微量磷元素的Ａｌ２２Ｓｉ合金粉末。研究了粉末形貌、粒度大小与分布，以及粉末显微组织，并初步探讨了微量磷对合金粉末特性影响的机理。结果表明，微量磷元素降低了粉末氧含量。其中含０．０４％磷的快冷Ａｌ２２Ｓｉ合金粉末球形粉末较高，平均粒度最小，粉末中初晶硅得到了进一步细化。     

Si对Al—SiC系润湿性的影响

用座滴法测定了真空条件下Al－9％Si、Al－13％Si、Al－18％Si三种铝合金与SiC的润湿角。并运用XRD、SEM、EDS等方法分析和探讨了Si对改善Al－SiC润湿性的作用机理。     

Influence of Silicon and Aluminum Additions on the Oxidation Resistance of a Lean-Chromium Stainless Steel

The effect of Si and Al additions on the oxidation of austenitic stainless steels with a baseline composition of Fe–16Cr–16Ni–2Mn–1Mo (wt.%) has been studied. The combined Si and Al content of the alloys did not exceed 5 wt.%. Cyclic-oxidation tests were carried out in air at 700 and 800°C for a duration of 1000 hr. For comparison, conventional 18Cr–8Ni type-304 stainless steel specimens were also tested. The results showed that at 700°C, alloys containing Al and Si, and alloys with only Si additions showed weight gains about one half that of the conventional type-304 alloy. At 800°C, alloys that contained both Al and Si additions showed weight gains approximately two times greater than the type-304 alloy. However, alloys containing only Si additions showed weight gains four times less than the 304 stainless. Further, alloys with only Si additions preoxidized at 800°C, showed zero weight gain in subsequent testing for 1000 hr at 700°C. Clearly, the oxide-scale formation and rate-controlling mechanisms in the alloys with combined Si and Al additions at 800°C were different than the alloys with Si only. ESCA, SEM, and a bromide-etching technique were used to analyze the chemistry of the oxide films and the oxide–base-metal interface, in order to study the different oxide film-formation mechanisms in these alloys.     

Effect of a grain refiner cum modifier on mechanical properties of Al-7Si and Al-11Si alloys

This study evaluates the influence of grain refiners/modifiers on the mechanical properties of the Al-7Si and Al-11Si alloys with an experiment of quantitative and qualitative correlations with the microstructure. Modification of Al-Si alloys with strontium additions and grain refinement with Al-Ti, Al-B and Al-T-B master alloy additions are demonstrated to be efficient on Al-Si alloys. A single master alloy with combined additions of Sr and Ti and/or B was prepared and the microstructure and mechanical properties were studied. The results show that boron rich (Al-3B-Sr and Al-1Ti-3B-Sr) master alloys are more efficient than Ti rich (Al-3Ti-Sr and Al-5Ti-1B-Sr) master alloys considering their combined grain refinement and modification effect on Al-7Si and Al-11Si alloys. However, the presence of Sr does not influence the grain refinement. Similarly, presence of grain refiner does not influence the modification of eutectic Si.     

Microstructure and hot cracking susceptibility of high conductivity Al–Fe–Si alloys

Aluminium–silicon based casting alloys have been extensively utilised in various industrial applications, but their relatively low electrical and thermal conductivities make them unsuitable for high conductivity parts. In this research, Al–Fe–Si based high conductivity alloys containing limited silicon content were investigated. Al–0·5Fe–xSi alloys with silicon ranging from 0·5 to 2% showed significantly higher electrical conductivity than conventional Al–Si based alloys. The hot cracking susceptibility of Al–Fe–Si alloys became seriously high as the Si content increased up to 1·5%, then susceptibility rapidly reduced with the further increase in Si. The relationship between solidification characteristics and hot cracking susceptibility of Al–0·5Fe–xSi alloys was discussed based on the thermal and cooling curve analyses and microstructural observations.     

Effects of flow of liquid filler metal and base metal composition on erosion characteristics during aluminium brazing

When automotive heat exchangers such as radiators and condensers are manufactured, serious erosion caused by the molten filler metal from the header occasionally occurs on the tubes during brazing. In our previous study, we proposed a novel experimental method which consisted of using a feeder and a base plate on a gutter made for the flow of molten filler, and we quantitatively evaluated the relationship between the volume of flowing molten filler and the level of erosion.

We used Al–12%Si molten filler to investigate the effect of chemical composition, in particular, the Si content of the base plane, on the level of erosion. When Al–0–1.2%Si alloys that have a solidus temperature that is higher that their brazing temperature were used, the level was almost constant irrespective of the Si content of the base metal. However, when Al–0–2.0%Si alloys that have a solidus temperature that is lower than their brazing one are used, the level increases.     

Influence of the microstructure on the machinability of heat-treated Al–10.8% Si cast alloys: Role of copper-rich intermetallics

This study was conducted with the intention of investigating a new experimental alloy, namely the 396 alloy which belongs to the Al–Si near-eutectic cast alloy group and contains about 10.8%Si. In the light of the above, the main purpose of the work is to report on the changes observed in the mechanical and machinability criteria resulting from the effects of the presence of two levels of Cu, namely 2.25% and 3.5%; and of the effects of two levels of Mg, namely 0.3% and 0.6%. In addition to the preceding, the effects of Mg-free alloys and Sr-modification on these same alloys were also investigated.The results demonstrate that the increase in the levels of Cu and/or Mg in the 396-T6 alloy has a detrimental effect on drill life. Such an effect may be attributed to the formation of large amounts of the coarse blocklike Al₂Cu phase, together with the formation of thick plates of the Al–Si–Cu–Mg phase. The Mg-free experimental alloy displays the lowest cutting force and moment in addition to producing the highest number of holes in the alloys studied. This observation may be explained by the cooperative precipitation of the Al₂Cu, Mg₂Si, Al₂CuMg, and Al₅Si₆Cu₂Mg₈ hardening phases in Mg-containing alloys which confer greater strength on the alloy than would be the case with the precipitation of only the Al₂Cu phase in the Mg-free alloy. A comparison of the non-modified alloy and the Sr-modified alloy (containing the same level of Mg and Cu additions) in terms of the number of holes drilled, reveals that the morphology of Si particles has a noticeable effect in governing the tool life of near-eutectic Al–Si alloys. The chip breakability of the alloys containing the Al₂Cu phase is superior to that of the alloys containing Mg₂Si. Thus, combined additions of Cu and Mg are expected to further refine the size of the chips produced.     

Si、Cu和热处理工艺对Al-Si合金电导率的影响

通过电导率测量、金相观察、扫描电镜分析和X射线衍射分析,研究了Si含量、Cu含量和热处理工艺对Al-Si系铸造合金晶格常数和电性能的影响规律。结果表明:Si和Cu元素的添加会减小合金的电导率;当Si含量超过固溶极限后,Si含量的变化对晶格畸变程度影响不大,合金的电导率受Si相的体积百分数控制;而Cu在固溶极限内时,随其含量的增加,晶格畸变程度增大,合金的电导率可根据铝基体晶格常数的偏离量来评估;经过450℃,5 h+250,2 h热处理工艺,晶格畸变程度明显降低,合金的电导率有明显提高,增幅最高可达32%。     

钛硅共晶系合金的微观组织与断裂特征

钛硅共晶系合金的组织形态与传统铸造钛合金组织完全不同，随着Si含量的增多合金塑性变差；断口形貌显示，合金的断裂为明显的脆性断裂，但不同类型的合金断裂机制又不尽相同。试验测试了亚共晶Ti-7%Si合金的共晶Ti-8.5%Si合金的室温和高温拉伸性能。     

Modification effect of pure rare earth metal La on as-cast hypereutectic Al-17%Si alloys

1　INTRODUCTIONImprovedpropertiesandlightweightareincreas inglybecomingthemaingoalsofautomotiveandaerospaceindustries[1] .Forthesakeofachievingthesecharacteristics,manyeffortshavebeenfocusedonaluminumalloysandtheirpropertiesundersevereconditions.Applyingaluminumalloystoautomotivepartssuchaspistons ,cylinderliners ,engineblocksanddifferentpartsofthermalmotors ,combinativeimprovementofthestrengthtomassratio ,wearre sistance,heatresistance ,andlowheatexpansionisanimportantgoal[2 ] .Al Siallo…     

Influence of Si content and heat treatment on microstructure of Al-Fe-Si alloys

The effect of Si addition and heat treatment on the Al-5wt.%Fe al oy has been investigated by OM, SEM-EDS and XRD. The results show that the Si plays a significant role in refining the primary Al3Fe phase. It was found that the addition of 3.0wt.% Si made the al oy present the finest and wel -distributed primary Al3Fe phase, but the Al3Fe phase almost disappeared when 5wt.% Si was added. With further increase in the Si content, some Fe-rich phases appeared in the inter-grains and coarsened. In addition, the heat treatments exert a significant impact on the microstructural evolution of the Al-5wt.%Fe-5wt.%Si al oy. After heat treatment for 28 hours at 590 oC, the coarse platelet or blocky Fe-rich phase in Al-5wt.%Fe-5wt.%Si al oys was granulated; the phase transformation from metastable platelet Al3FeSi and blocky Al8Fe2Si to stable Al5FeSi had occurred. With the extension of heat treatment, the Si phase coarsened gradual y.     

Effect of Strontium on the Oxidation Behavior of Liquid Al–7Si Alloys

The oxidation behavior of small amounts of Al–7Si alloys containing strontium and magnesium has been investigated using thermal gravimetrical analysis (TGA). The results of TGA experiments showed that Sr-additions increase the oxidation rate of the Al–7Si alloys melt significantly. A noticeable content of SrO-containing mixed oxides was found, using scanning electron microscopy (SEM), on the oxidized surfaces after even short oxidation periods. The rapid rate of Sr-loss during the oxidation periods also showed that Sr was highly reactive in the small melts for oxidation. The oxidation of large Al–7Si melts was also studied by analyzing the surface layer at different periods. The surface oxide layers on the large melts consisted of Al₂O₃ and Al₂O₃ · MgO but were found to contain no detectable SrO. Also, in contrast with the small melts, the relatively slow rate of Sr-loss during the oxidation period showed that strontium has good stability in a large melt, revealing that in such cases the tendency of Sr for oxidation is not noticeable.     

Effect of strontium on crystallization of Mg2Si phase in Al—Si—Mg casting alloys

Otical microscope and SEM were used to observe the changes of the microstructure of Al-11.6%Si-0.4% Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg2Si phase was discussed.It is found that Mg2Si phase nucleastes on the the surfaces of the eutectic silicon flakes in the unfully modified alloys,growing as meshwork or bamboo-shoot shape,however,very few and fine Mg2Si particles phase are isolated at the boundaries of the eurectic cells in the fully modified alloys.Strontium has an important influence on the crystallization of Mg2Si phase in the Al-Si-Mg casting alloys and it is thought to be related to the increase of the amunt of dendritic αphase and the modifying degree of eutectic silicon phase.     

EFFECTS OF COMBINED ADDITIONS OF TUNGSTEN AND MOLYBDENUM ON THE CREEP PROPERLIES OF Fe_3Al-BASED ALLOYS

1. IntroductionIron aluminides based on Fe3AI have been interested since the 1930's when their excellent oxidation resistance was first .oted[1'2]. However, poor high--temperature creepresistance is one.of major deterrents to their development as structural materials. Recentdevelopmental efforts have indicated that the creep resistance can be improved by alloyingprocesses, and the effect of some elements such as Cr, Mo, W, Nb, or Zr on the creep resistance of Fe3AI has been investigated re…     

铸态亚共晶Al-Si合金中初生硅的生长机制(英文)

利用光学显微镜和电子背散射衍射技术观察亚共晶Al-10%Si合金的微观结构特征。结果表明,在亚共晶合金内很容易发现初生硅颗粒。研究亚共晶Al-10%Si合金溶液中初生硅析出过程中的晶核形成和生长机制,发现硅原子容易偏析并形成Si-Si簇,即使在共晶和亚共晶合金内,这一现象也会导致初生硅的形成。另外,由化学驱动力和较大的堆积碰撞或溶质的凝固偏析等原因引起的溶质再分配在初生硅的形成过程中也起着重要的作用,其中溶质再分配方程由Jackson-Chalmers方程推导而出。一旦硅溶质浓度超过共晶成分,在固/液界面的前端就会析出初生硅。     

Physical properties of selected brazing filler metals

Abstract

A suitable selection of the filler metal is vital for producing satisfactory brazed joints. The wettability of brazing alloys with base metals depends on physical properties such as surface tension, density, melting point, and viscosity. Thermal conductivity and electrical resistivity are also important since the filler metal is frequently required to have similar values to those of the base metal. In the present paper, the physical properties of liquid alloys relevant to brazing have been evaluated. Six different filler metal systems were analysed, comprising alloys based on Ag, Al, Au, Cu, Ni, and Ti. Results show that the viscosity values for most binary brazing filler alloys are of the order of 2–8 mPa s, with Cu and Al alloys exhibiting the lowest viscosities. The surface tensions of brazing alloys vary from 800 to 1800 mN m^-1, with the lowest surface tension values corresponding to the Ag and Al alloys. Thermal conductivity and electrical resistivity values fall in the range 10–200 W m^-1 K^-1 and 17–300 μΩ cm, respectively.     

Temperature-dependence of electrical resistivity of Cd-Sn, Bi-Sn, and Al-Si eutectic and Al-3wt.%Si hypoeutectic alloys

Cd-Sn, Bi-Cd, and Al-Si eutectic and Al-3wt.%Si hypoeutectic alloys of high-purity (99.99%) metals were produced in a vacuum atmosphere. Current-voltage (I-V) characteristics of these specimens were measured at various temperatures between 100 and 475 K. The electrical resistivity (ρ) and temperature coefficient (α) for each specimen, depending on the temperature, were calculated using results obtained from the I-V measurements. The electrical resistivities and the residual resistivity of the specimens increase with increasing temperature for each alloy system. These results are compared with literature results.