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1.
采用喷射成形技术制备了过共晶Al-Si耐磨合会,分析了合金的显微组织结构,利用M200磨损试验机对喷射成形和铸造Al-Si合金的耐磨性和磨损失效形式进行了分析比较。结果表明:喷射成形能够显著改变过共晶Al-Si合金中初晶Si相的形态和尺寸,细化合金的基体组织;与普通铸造合金相比,具有更好的耐磨性能。  相似文献   

2.
本文即针对喷射成形共晶铝硅合金成形性进行研究 ,采用Gleeble15 0 0实验机进行压缩比实验 ,并同时量测流动应力。本研究以涡卷式压缩机用之涡卷转子为载具 ,进行共晶铝硅合金锻件的开发分析。试锻结果确认喷射成形共晶铝硅合金具有近似于 60 61及 40 3 2的成形性 ,在相同锻造条件下 ,涡卷端面平面度与 60 61及 40 3 2并无显著差异  相似文献   

3.
The microstructure evolution of an extruded Mg-8.57Gd-3.72Y-0.54Zr (mass fraction, %, GW94) alloy during reheating into the semisolid state was investigated using optical microscopy (OM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). Typical semisolid microstructure with globular solid particles distributed in the liquid matrix is obtained over 600 °C. The solid content of (Gd+Y) in the primary a-Mg particles decreases with increasing the semisolid temperature. With the prolongation of isothermal holding time, the liquid fraction does not change significantly, while the grains grow up and spheroidize. Three methods used to determine the liquid fraction as a function of temperature, namely quantitative metallography on quenched microstructures, cooling curve thermal analysis, and thermodynamic calculations were further compared.  相似文献   

4.
Mechanical properties of hypereutectic Al-Si alloy by semisolid processing   总被引:3,自引:1,他引:2  
1 INTRODUCTIONHypereutecticAl Sialloysownexcellentwearresistance .However ,thesizeandmicrostructureofprimarysiliconhave greateffectonits properties ,thenthepresentstudiesmainlyfocusontheimprove mentoftheprimarysiliconsizeandmicrostructurebymeansofmodifica…  相似文献   

5.
The hypereutectic Al-Si alloy was fabricated by hot extrusion process after solidified under electromagnetic stirring,and the microstructure and mechanical properties of the alloy were studied.The results show that the ultimate tensile strength and elongation of the alloy reached 229.5 MPa and 4.6%,respectively with the extrusion ratio of 10,and 263.2 MPa and 5.4%,respectively with extrusion ratio of 20.This indicates that the mechanical properties of the alloy are obviously improved with the increase of extrusion ratio.After hot extruded,the primary Si,eutectic Si,Mg2Si,AlNi,Al7Cu4Ni and Al-Si-Mn-Fe-Cr-Mo phases are refined to different extent,and the efficiency of refinement is obvious more and more with the increase of extrusion ratio.After T6 heat treatment,the sharp corners of these phases become passivated and roundish,and the mechanical properties are improved.The ultimate tensile strength of the extruded alloy after T6 heat treatment reaches 335.3 MPa with extrusion ratio of 10 and 353.6 MPa with extrusion ratio of 20.  相似文献   

6.
The microstructure and mechanical properties of Al-14.6Si castings modified by Cu-P master alloy under different conditions were studied with optical microscope(OM) and mechanical testing and simulation(MTS).The results indicate that the Cu-P master alloy possesses not only obvious modification effect,but also longevity effect with more than 8 h on the hypereutectic Al-Si alloy.It is shown from thermal calculation,scanning electron microscope(SEM),and energy dispersive analysis of X-rays(EDAX) that the modification mechanism of Cu-P on primary silicon in the castings is heterogeneous nucleation around AlP particles.The Cu-P master alloy has no or little modifying effect on eutectic silicon,even though it has obvious modification on primary silicon in the castings.This may be because of the fast transformation of eutectic silicon at a very narrow temperature,which will notably weaken the role of AlP particles as heterogeneous nuclei for eutectic silicon.  相似文献   

7.
The effects of vibration and grain refiner on the microstructure of semisolid slurry of hypoeutectic Al-Si alloy were studied. The impact of vibration on the convection of liquid was conducted by using a system of water-particle tracer. The 356 melt at temperature of 630-660 ℃ with or without grain refiner Al-5%Ti-1%B was poured into a metal cup as the vibrating vessel, then it was cooled to 590-610 ℃ in the semisolid zone and kept for some time, subsequently vibration with different frequencies was applied. The results show that the primary a(Al) particles become finer and rounder with the increase of vibration frequency. The slurry with primary a(Al) equivalent particle diameter(EPD) of about 90μm and average shape coefficient(ASC) of about 0.5 can be prepared under vibration of 20 Hz. With the combined action of vibration and grain refiner Al-5Ti-B, even smaller and rounder spheroids with EPD of about 85μm and ASC of about 0.6 are obtained.  相似文献   

8.
The numerical simulation for microstructure evolution of Al-Si alloy in solidification process is carried out with phase field model. The phase field model, solution algorithm and the program of dendrite growth are introduced. The definition of initial condition, boundary condition and the stability condition of differential format are all included. The simulation results show that the evolution of dendrite morphology is as follows: the initial circle nucleus transforms to the rectangle one firstly, then its corners develop to the four trunks and from which the secondary side branches are generated and even the third side branches are produced from secondary ones. The dendrite tip radius decreases quickly at the initial stage and changes slowly at the late stage, which is mainly due to the fact that more and more side branches appear and grow up. The comparisons of dendrite morphology between simulated results and investigations by others are also presented. It is proved that the dendrite morphologies are similar in trunks and arms growth, so the developed phase field program is accurate.  相似文献   

9.
喷射成形Mg-9Al-xZn合金的微观组织演变   总被引:1,自引:0,他引:1  
利用喷射成形技术制备AZ91、AZ92和AZ93镁合金沉积柱坯,并对其微观组织演变进行观察.结果表明:铸态普通凝固AZ91合金的晶粒粗大,脆性β-Mg17Al12相连续分布成网状结构;而喷射成形AZ91、AZ92和AZ93合金的组织均匀,晶粒被充分细化,β-Mg17Al12相的网状结构被打破;喷射沉积快速凝固条件下高的冷却速率促进了过饱和α-Mg固溶体组织的形成,使得偏析相减少,形态改善;Zn含量的增加降低了Al在Mg中的溶解极限,促进了β-Mg17Al12相在晶界的析出及α-Mg+β-Mg17Al12离异共晶组织的形成;Zn元素的偏析倾向为激活成分过冷区内的形核质点提供了驱动力,从而阻碍了晶粒长大.  相似文献   

10.
11.
1 INTRODUCTIONThemicrostructureofhypereutecticAl Sialloys ,preparedbyconventionalcastingroutines ,usuallyconsistsofcoarseSicrystals[112 ] ,leadingtothepoorextrudability ,machinability ,strengthandductili ty[1315] .Therefore ,structuralmodificationmustbedonethroughtwo generalways :1)alloyingaddi tions ,and /or ;2 )syntheticalternatives .Accordingtothedimensionalconditionofaneffectivemodifier ,theradiusratiooftheagenttoSishouldbeabout1.6 5 [16 ] ,La ,withtheratioof 1.5 9,ispossiblycon sid…  相似文献   

12.
综述了为改善过共晶铝-硅合金的性能,目前所采用的控制合金中初晶硅尺寸、形态和分布的各种处理方法及其机制,它们包括细化变质、合金熔体过热处理、半固态搅拌、快速凝固、电磁场作用、电脉冲孕育处理等方法。从合金中初晶硅尺寸、形态和分布等方面比较了各种处理方法的优缺点。  相似文献   

13.
Rapidly solidified hypereutectic Al-Si alloys were prepared by powder hot extrusion.By eliminating vacuum degassing procedure.the fabrication routine was simplified.The tensile fracture mechanisms at room temperature and elevated temperature were investigated by SEM fractography.Compared with KS282 casting material,the tensile strength of rapidly solidified Al-Si alloy is greatly improved due to silicon particles refining while its density and coefficient of thermal expansion are lower.than those of KS282.The wear resistance of RS AlSi is better than that of KS282.  相似文献   

14.
过共晶Al-Si合金变质处理研究进展   总被引:1,自引:0,他引:1  
综述了目前常用过共晶Al-Si合金变质处理方法和特点,介绍了各变质处理方法的发展概况及新的研究成果,指出低成本、高效、无污染、多功能化的复合变质是变质处理的发展趋势.  相似文献   

15.
A new modifying agent, ZnS, was used as a refiner to modify primary silicon in hypereutectic AlSi alloy. The factors affecting the modification results, including addition level of ZnS and holding time, were investigated. The results showed that the average size of the most effectively modified primary silicon was 28.5 μm when the ZnS mixed powder addition was 0.15 wt.% with a holding time of 10 min. More important, the average size of primary silicon could remain below 40 μm despite the holding time extending to 120 min, which means ZnS is a promising modifying agent of primarySi in industrial applications.  相似文献   

16.
对不同的工艺条件下制做的铝-硅基复合材料中硅相组织进行了研究。结果表明,冷却速度增大,热处理保温时间适当增长都会使基体组织中的硅相形态由块状向粒子状转变,促使硅相细化;另外,提高热处理温度使复合材料出现新相(α-Al);凹曲面的增强相表面形态有利于细化复合材料组织。  相似文献   

17.
A self-made single-roll stirring (SRS) machine was used to manufacture semisolid A2017 alloy, the mechanismof A2017 alloy formation was investigated. It was shown that A2017 dendrites growing on the rough roll surface arecrashed into fragments by the roll, which move and grow freely then contribute the formation of finer spherical microstruc-ture. When casting at 710-750 ℃, fine and homogeneous spherical or elliptical grains of A2017 alloy were obtained. Ex-tending forming mould has been designed and was installed at the exit of roll-shoe gap. A2017 alloy was formed by ex-tending continuously at the semisolid state on SRS machine. Through controlling pouring temperature, semisolid formingand extending extrusion was combined organically. A2017 product with fine surface and rectangular transection of 14mmx25 mm was obtained. By contrast to the national standard, the fracture strength and elongation of A2017 products pro-duced from extending semisolid extrusion have been improved with an increase of 100 MP  相似文献   

18.
1 INTRODUCTIONThe phasediagramsofimmisciblealloysarecharacterizedbythepresenceofamiscibilitygap—aregioninwhichtwoliquidphasesco e  相似文献   

19.
综述了挤压温度、挤压比对喷射沉积高Si铝合金微观组织和力学性能的影响。比较了不同合金成分的高Si铝合金的力学性能。  相似文献   

20.
A two-step reheating process was proposed and applied to perform reheating experiments on the semi-solid 2024 alloy billet. In this process, the semi-solid billet was firstly heated over liquidus temperature and then isothermally held at solid-liquid zone temperature. Microstructure evolution of the semi-solid billet during two-step reheating was studied by optical microscope and compared with that during isothermal reheating. The results show that the remelting rate of the semi-solid billet during two-step reheating is faster than that during isothermal reheating. Under the same reheating time, the grains of the semi-solid billet reheated by two-step reheating process are finer and rounder than those by isothermal reheating process. The present experimental results indicate that accelerating the formation of liquid phase during the two-step reheating process can restrain the coalescence of grains to a certain extent, and thus refine the grain size and promote the grain spheroidization.  相似文献   

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