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1 INTRODUCTIONAsoneofthelighteststructurematerials ,mag nesiumalloysofferlightmass(ρ<2 g·cm- 3) ,specif icstrength (higherthanthatofthealuminumalloysandsteels) ,specificstiffness ,excellentmachinabili ty ,superiordampingandmagneticshieldingcapaci ties,whichleadstoagrowinginterestinmagnesiumanditsalloys .Inrecentyears ,magnesiumalloyshavebeenwidelyusedinaviation ,spaceflight,automobileandelectronicsindustries[1] .Since 1990 stheirappli cationhassteadilyextendedanditispredictedthatitwill… 相似文献
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Structure evolution of AZ61 magnesium alloy in SIMA process 总被引:1,自引:0,他引:1
The effect of prior compressive deformation, isothermal temperature and holding time on the structure of AZ61 magnesium alloy fabricated by strain-induced melt activation(SIMA) processing was investigated. The specimens were subjected under deformation ratios of 0%, 22% and 40% and various heat treatment time and temperature regions. The results indicate that the ideal technological parameters of semi-solid AZ61 alloy produced with non-dendrites are recommended as 22% (prior compressive deformation), 595℃ (heat treatment temperature) and 40 min(time). The as-cast AZ61 magnesium alloy isn‘t fit for semi-solid forming. 相似文献
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Effects of holding temperature and time on semi-solid isothermal heat-treated microstructure of ZA84 magnesium alloy 总被引:1,自引:0,他引:1
The feasibility of fabricating ZA84 magnesium alloy with non-dendritic microstructure by a semi-solid isothermal heat treatment process and the effects of holding temperature and time on the semi-solid isothermal heat-treated microstructure of the alloy were investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by suitable semi-solid isothermal heat treatment. After being treated at 560-575℃ for 120min, ZA84 magnesium alloy can obtain a non-dendritic microstructure with 14.2%-25.6% liquid fraction and an average size of 56-65μm of the unmelted primary solid particles. With the increasing holding time from 30 to 120min or holding temperature from 560 to 575℃, the average size of unmelted primary solid particles decreases and globular tendency becomes more obvious. Under the experimental condition, the microstructural evolution of ZA84 alloy during semi-solid isothermal treatment is mainly composed of three stages of initial coarsening. structulseparation and spheroidization. The subsequent coarsening of spheroidal grains is not observed. 相似文献
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采用施加超声场来实现AZ80镁合金熔体净化,研究不同功率、不同处理时间及不同静置时间对AZ80镁合金净化的影响。结果表明:超声处理镁合金熔体可以加速熔体中夹杂物的分离,实现熔体的净化。当镁合金熔体在650℃经超声功率80W,处理时间60s及静置时间100s时熔体净化效果最好。铸锭中夹杂物越多电导率越小,电导率可以表征铸锭的净化程度。 相似文献
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新SIMA制备坯料触变挤压AZ61镁合金零件的组织与性能(英文) 总被引:1,自引:0,他引:1
新应变诱导熔化激活法被用来制备高质量的AZ61镁合金半固态坯料。利用光学显微镜和拉伸实验,研究触变挤压成形零件的微观组织与力学性能。结果表明:当施加的压力为784MPa,保压时间为90s,模具温度为450℃时,半固态坯料能够完全充填模具型腔。与半固态等温处理方法相比,新SIMA法制备的半固态坯料触变挤压成形零件的抗拉强度和伸长率分别为300.5MPa和22%;并且成形零件的微观组织晶粒细小、组织均匀。随着等温处理温度的升高和保温时间的延长,成形零件的抗拉强度和伸长率先增加后降低。当挤压道次从1增加至4时,成形零件的抗拉强度和伸长率明显增加。 相似文献
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It was attempted to enhance and accelerate the separation of oxidation inclusions from magnesium alloy melt by virtue of ultrasonic agglomeration technology. In order to investigate the feasibility and effectiveness of standing waves for ultrasonic purification of magnesium alloy melt, numerical simulation and relevant experiment were carried out. The numerical simulation was broken into two main aspects. On one hand, the ultrasonic field propagations within the cells with various shapes were characterized by numerical solutions of the wave equation and with a careful choice of geometry a nearly idealized standing wave field was finally obtained. On the other hand, within such a standing wave field the agglomeration behavior of oxidation inclusions in magnesium alloy melt was analyzed and discussed. The agglomeration time and agglomeration position of oxidation inclusions were predicted with numerical simulation method. The results show that the oxidation inclusions whose apparent densities are close to the density of the melt can agglomerate at wave nodes in a short time which to a great extent enhances and accelerates the separation of oxidation inclusions from magnesium alloy melt. 相似文献
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Cracks and ruptures always occur during wire drawing process of 42% nickel-iron expansive alloy. In order to study the reasons of these phenomena, a method of metallographic observation in combination with sample electrolysis was used to characterize the non-metallic inclusions in the alloy wire. The results indicate that the inclusions in the alloy are oxidation products during the process of melting. There are single or complex phase inclusions composed of elements such as Al, Si, Ca, Ti, Fe, and O2. Among them, the macro-inclusions are TiO2 compound inclusions formed by the adhesion of Al and Si oxides on them. These inclusions are fragile ones with a low strain rate, as well as a rather high hardness, so that they are the main reason that leads to the surface cracks and ruptures in the alloy wires. The analysis has educed that the key point to enhance the product quality is to promote the cleanliness of the melt, control the types and quantity of non-metal inclusions in the alloy. 相似文献
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The semisolid slurry of the A356 aluminum alloy was prepared by self-inoculation method (SIM), the effects of melt treatment temperatures and isothermal holding parameters on water-quenched microstructures of A356 aluminum alloy semisolid slurry were investigated, and the solidification behavior of the remaining liquid phase (secondary solidification) was analyzed. The results indicate that the melt treatment temperature has significant effects on the final semisolid microstructures. The semisolid slurry which is suitable for the rheological forming can be produced when the melt treatment temperature is between 680 and 690 °C. During the isothermal holding process, the growth rate of the primary particles conforms to the dynamic equation of Dt3–D03=Kt, and the coarsening rate of the primary particles is the fastest when the isothermal holding temperature is 600 °C. Additionally, the isothermal holding time also has obvious effect on the secondary solidification microstructures. The secondary particles are the smallest and roundest when the isothermal holding time is 3 min. The amount of the secondary particles gradually increases with the increase of isothermal holding temperature, and the eutectic reaction therefore is confined into small intergranular areas, contributing to the compactness of the final solidified eutectic structures. 相似文献
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Non-flux purification behavior of AZ91 magnesium alloy 总被引:1,自引:0,他引:1
The effects of non-flux purification techniques on the mechanical properties and microstructure of AZ91 magnesium alloy were investigated by ICP,OM,XRD and SEM.The results show that Ar spraying with high flow rate could remove non-metallic inclusions and improve the mechanical properties of AZ91.The alloy obtains the best properties after argon spraying for 30 min at the melt temperature of 740 °C.The ceramic foam filter(CFF) could effectively improve the ultimate tensile strength and elongation of AZ91 alloy,especially the elongation,which increase with increasing pores per inch(ppi) and the thickness of CFF.Non-flux purification does not change the microstructure of AZ91 alloy.However,filtration has a certain effect on the fracture pattern of AZ91 alloy.To improve the mechanical properties effectively,both filtration and gas spraying should be utilized together. 相似文献
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H. Mohammadi M. Ketabchi A. Kalaki 《Journal of Materials Engineering and Performance》2011,20(7):1256-1263
Microstructural evolution of semi-solid 7075 Al alloy manufactured by strain-induced melt activation (SIMA) process was investigated.
The effects of different processing parameters, such as isothermal temperature and holding time on the semi-solid microstructures
(the liquid volume fraction, average grain size, and degree of spheroidization of the solid particles) during partial remelting
have been investigated on 7075 Al alloy that was extruded by an extrusion ratio of 20 before remelting. Experiments of remelting
were carried out in the range of 560-610 °C for 10, 20, and 30 min holding time and then the specimens were quenched in cold
water. Microstructure of quenched samples were observed under optical microscope and then analyzed via image analysis. The
results showed that high semi-solid isothermal temperature would increase the liquid volume fraction and accelerate the spherical
processing of the solid particles. Furthermore at long holding time, the globular grains coarsened slightly and the average
grains size are increased. The experimental results showed that the optimum process parameters, should be chosen at isothermal
temperature of 580 °C with the holding time, <30 min. 相似文献
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Purification technology of AZ91 magnesium alloy wastes 总被引:7,自引:0,他引:7
1 INTRODUCTIONBecausemagnesiumalloyhastheadvantagesoflowdensity ,highspecificstrengthandrigidity ,ex cellentdampingeffect,goodtolerancetoimpact ,ex cellentmachinabilityandpolishingability[1,2 ] ,itiswidelyusedinthefieldsofautomobilemanufactur ing ,aviationandspaceflight,communication ,opticinstrumentsandcomputermanufacturing[35] .How ever ,theyieldofmagnesiumalloyislowinthepro ductionofdiecasting .Atpresent ,theutilizationra tiocanonlybeabout 30 % 5 0 % .Intheprocessofdiecasting ,alargeq… 相似文献
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The feasibility of fabricating ZL104 aluminum alloy with non-dendritic microstructure by semi-solid isothermal heat treatment process and the effects of holding temperature and time on the semi-solid isothermal heat-treated microstructure of the alloy, are investigated. The research results indicate that it is possible to produce ZL104 alloy with non-dendritic microstructure by a suitable semi-solid isothermal heat treatment. After treated at 580 ℃ for 120 min, the ZL104 alloy can obtain a non-dendritic mic... 相似文献
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自孕育法制备AZ31镁合金半固态流变成形组织(英文) 总被引:1,自引:0,他引:1
采用新型自孕育流变铸造技术对变形镁合金半固态组织进行控制。该工艺过程为将合金熔体与一定量的合金固体颗粒(自孕育剂)混合,然后将混合金属通过一个多流股导流器浇入铸型或收集器。结果表明:采用自孕育工艺,合金熔体处理温度690~710℃,孕育剂的加入量为3%~7%时能有效将AZ31镁合金传统铸造中的粗大枝晶组织转变为细小、近球状的非枝晶组织;当合金熔体处理温度较高时,增加孕育剂的加入量或减小导流器的倾斜角度有利于获得非枝晶组织。自孕育工艺制备的AZ31镁合金半固态浆料在620℃等温保温30s后能有效改善初生α-Mg颗粒的圆整度;延长保温时间有助于减小颗粒的圆整度,但同时颗粒发生粗化。利用Lifshitz-Slyozov-Wagner(LSW)理论对初生相颗粒在等温保温过程中的组织圆整、粗化过程进行了分析。 相似文献
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等温热处理工艺参数对Mg-8%Al-1%Si合金半固态显微组织的影响(英文) 总被引:1,自引:0,他引:1
采用等温热处理工艺制备具有半固态显微组织的Mg-8%Al-1%Si合金,研究等温热处理工艺参数(等温温度和等温时间)对Mg-8%Al-1%Si合金显微组织的影响。结果表明:通过等温热处理工艺可以得到具有非枝晶组织的Mg-8%Al-1%Si合金。随着等温温度从560°C升高至575°C或等温时间从5min延长至30min,半固态组织中的液相体积分数增加,α-Mg晶粒尺寸变大并且其球化趋势明显。此外,在半固态组织中的共晶Mg2Si相从汉字状转变成为颗粒状。研究等温热处理Mg-8%Al-1%Si合金中的共晶Mg2Si相的形貌转变机制。 相似文献
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研究了铸造Al-7Si-4Cu合金在半固态等温处理过程中组织、性能的变化。结果表明,通过调整等温处理时间、温度不仅可以改善铸造铝硅铜合金的组织,而且提高了合金的力学性能。在一定的冷却速率下,适当延长等温处理时间、提高等温处理温度有利于硅相的圆整化、细化。在半固态温度下进行保温,当保温时间为5min时,可获得弥散相,保温温度高,弥散相多;延长保温时间至10min,未发现弥散相析出,而硅相圆整、细小,分布均匀,弥散相多,合金硬度就高。 相似文献
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半固态LY11铝合金的组织演变研究 总被引:9,自引:1,他引:9
对LY11合金的应变诱发熔化激活法(SIMA)制备工艺进行了研究,定量分析了变形量(ε)、等温温度(Ti)、保温时间(t)等工艺参数和预处理技术对晶粒尺寸、分形维数和晶粒尺寸分布等的影响,讨论了晶粒的大小、形状、尺寸分布的演变规律。结果表明:变形量对晶粒大小、形状的变化影响极大,要获得细小、近球形的晶粒需足够的变形程度;升高等温温度和延长保温时间会促使晶粒长大、球化;所有试样的晶粒尺寸呈正态分布,随着变形量的减小、等温温度的升高和保温时间的延长,峰值点附近晶粒的数目逐渐减小,尺寸逐渐增加;冷、热变形预处理条件对组织演变产生一定的影响,给试样施加变形是SIMA工艺的必要步骤。 相似文献