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ZA27合金250℃时效时间对阻尼性能的影响 总被引:5,自引:0,他引:5
研究了淬火态ZA2 7合金在 2 50℃下时效不同时间后的阻尼性能。结果表明 ,ZA2 7合金时效0 5h后 ,组织由细小层片状α相和 η相组成。随时效时间延长 ,相组成和相成分不变 ,但层片厚度和层片间距加大 ,层片长度先增加后缩短 ,组织不断粗化。时效 4h后 ,组织趋于稳定。与淬火态相比 ,时效使合金的阻尼性能提高 ,时效 4h后合金阻尼达到稳定值。其中室温下 32 0Hz时的阻尼为 1 2× 1 0 -3 ,0 1Hz时的阻尼为 6 2 1× 1 0 -3 。与铸态合金相比 ,时效使合金阻尼降低。研究发现 ,ZA2 7合金的阻尼随温度的升高单调增大 ,并与频率相关。当温度较高时 ,随着频率增大 ,阻尼值减小 相似文献
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稀土对ZA27合金阻尼性能的影响 总被引:5,自引:2,他引:5
谭银元 《特种铸造及有色合金》2002,(2):53-54
研究了稀土对ZA27合金阻尼性能的影响规律。结果表明:稀土变质可提高ZA27合金的阻尼性能,经稀土变质后的试样,其内耗是未变质的试样的1.4倍。ZA27合金为发挥其阻尼作用,在频率高于70Hz时,效果明显,且经稀土变质后的试样强迫振动衰减效果比未变质的试样强。 相似文献
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ZA27-4%Si合金的阻尼性能及阻尼机理 总被引:7,自引:0,他引:7
利用低频内耗测试技术研究了ZA27-4%Si合金的阻尼性能, 分析了合金的阻尼机理. 结果表明 ZA27-4%Si合金阻尼随频率增大而减小, 随温度升高而增大, 阻尼不随应变振幅的变化而变化ZA27-4%Si合金室温阻尼为5.83×10-3, 与ZA27合金阻尼相当ZA27-4%Si合金的阻尼是由合金内部的晶界和相界面滑动、位错振动以及各相的热膨胀系数和弹性模量间差造成的微塑性变形共同造成的. 硅合金化的ZA27合金具有良好耐磨减摩性能和减振性能. 相似文献
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ZA27合金的微观组织 总被引:35,自引:2,他引:35
用SEM和TEM对金属型铸造并经 18个月自然时效的ZA2 7合金的微观组织进行了观察。结果表明 :ZA2 7合金凝固的初生相为富Al的树枝状α′相 ,随后在α′相周围形成一层富Zn的包晶 β相 ,最后剩余液体发生共晶反应 ,共晶 β优先依附于包晶 β相形核、长大 ,而共晶 η则在包晶 β相间形成一层薄膜 ,在有些区域则形成棒状共晶组织 ;在随后的冷却及时效过程中 ,β发生胞状分解形成规则的共析α η层片组织或不规则的复杂形状组织 ,共析胞以共晶 η相为基形核 ,并向枝晶中心生长 ,使α′相也分解为层片α η组织 ,当其生长被α′中心的连续分解所阻挡时 ,致使其芯部形成细小的α η颗粒组织 ;富Cu的ε相存在于所有 η相中 相似文献
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通过对锌铝合金ZA27进行365℃固溶和250℃人工时效,在0.1、0.3、1.0Hz 3个振动频率下,测试了铸态和固溶时效态合金从室温到400℃的阻尼随温度、频率、应变振幅的变化规律,研究了阻尼行为与相应微观组织之间的关系。根据Al-Zn二元合金平衡相图,分析了ZA27合金在平衡和实际冷速下所结晶的铸态和固溶时效组织。结果表明:铸态ZA27合金阻尼的大小与频率有关、与应变振幅无关;在300℃附近阻尼-温度曲线出现的阻尼峰位不随频率的改变而移动,说明在此温度有一级固态相变;经固溶时效后,合金组织明显细化,阻尼特性基本不变,但阻尼峰值明显高于铸态合金,表明固溶时效不改变ZA27合金的阻尼特性,但显著提高了合金的阻尼。 相似文献
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通过OM、SEM和XRD对触变成形并经5年自然时效的ZA27合金的微观组织进行了观察。结果表明:经触变成形后的ZA27合金由球状初生粒子α′相、晶间的二次凝固组织及半固态成形时没有凝固完全的小液池组成。共晶方式主要为离异共晶及其中"蜂窝"状棒状共晶,部分区域出现不规则层片共晶。ZA27合金在后期的冷却和自然时效过程中,经过了一系列的相变,β相发生胞状分解,形成规则的共析α+η层片组织或不规则的复杂形状组织,从一些层片区域逐渐向低铝的α′相区域中心生长为粗大的层片组织,当其生长被α′中心的连续分解所阻挡时,在其芯部形成细小的α+η颗粒组织。 相似文献
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研究了CuAlBeX合金淬火及淬火时效态的阻尼性能,结果表明:该合金淬火后经300℃时效会产生一种新的马氏体,该马氏体的存在,严重影响了合金的阻尼性能。 相似文献
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The authors investigated the effects of the isothermal heat-treatment conditions on the microstructural evolution and composition
distribution of semisolid Al-4Cu-Mg alloy during isothermal heat treatment. The experimental results show that the microstructural
evolution and composition distribution of semisolid Al-4Cu-Mg alloy are controlled by atom diffusion during the isothermal
heat treatment process. Grain growth and spheroidization were promoted with the increase of the isothermal temperature and/or
the holding time. Moreover, the higher the isothermal temperature, or the longer the holding time, the more segregation constituent
elements occurred to the grain boundaries. The low melting structure at grain boundary is greatly affected by Cu. The microstructural
evolution in the isothermal heat-treatment process is as follows: recovery, recrystallization, fragmentation, spheroidization,
and coarsening. Such fragmentation, spheroidization, and grain growth of coalescence and Ostwald ripening are involved as
main mechanisms in the isothermal heat-treatment process. 相似文献
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Al-Zn-Mg-0.25Sc-Zr合金的热压缩变形行为和微观组织演化(英文) 总被引:1,自引:0,他引:1
采用等温轴对称热压缩实验对Al-Zn-Mg-0.25Sc-Zr合金的热变形行为和微观组织演化进行研究。变形温度为340~500°C,应变速率为0.001~10 s-1。结果表明:稳态流变应力随着应变速率的增加和变形温度的降低而增大,该合金的流变应力行为可用双曲正弦形式的本构方程来描述,其变形激活能为150.25 kJ/mol。在变形温度较高和应变速率较低(即Z参数较低)的条件下,动态再结晶更容易发生。随着Z参数的变小,合金的主要软化机制由动态回复转变为动态再结晶,合金中的位错密度降低,亚晶尺寸增大。 相似文献
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添加0.5%富铈混合稀土AZ91D镁合金半固态组织的形成 总被引:1,自引:1,他引:1
半固态浆料的固相颗粒尺寸、形态和分布主要取决于熔化过程中液相的形成与演化过程。采用添加0.5%富铈混合稀土来改善AZ91D镁合金的铸态组织,研究在半固态等温热处理中的组织演变以及非枝晶组织制备与控制的机理。结果表明:稀土合金化处理可促进初生相在等温热处理过程中由枝晶向粒状晶的转变,可获得更加细小、均匀的球状固相颗粒,并且其粗化速度较慢。半固态等温热处理过程中,整个系统处于熔化和结晶的动态平衡,铸态组织中枝晶根部高溶质浓度区或系统的温度、浓度起伏是固相颗粒内液相形成的内在和外在条件。 相似文献
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固溶处理及时效对镍钛形状记忆合金组织演化及力学性能的影响 总被引:1,自引:0,他引:1
将镍钛形状记忆合金Ni50.9Ti49.1(摩尔分数)在1123 K固溶处理2 h,然后分别在573、723和873 K时效2h。采用透射电镜、高分辨率透射电镜、扫描电镜和压缩实验,系统研究固溶处理和时效对镍钛合金组织演化及力学性能的影响。结果表明:固溶处理有助于消除原始镍钛样品中的Ti2Ni相,但不能消除TiC相。固溶处理导致镍钛合金中原子排列的有序畴界。在所有时效镍钛样品中,Ni4Ti3析出相、R相和B2奥氏体相共存于室温下的镍钛基体上,然而在873 K时效的镍钛样品中,可以观察到马氏体孪晶。在573和723 K时效的镍钛样品中,细小密集的Ni4Ti3相均匀分布在镍钛基体上,而且与B2基体保持共格关系。然而,在873 K时效的镍钛样品中, Ni4Ti3相尺寸非常不均匀,和B2基体保持共格、半共格和非共格关系。在723 K时效的条件下,细小均匀的Ni4Ti3相阻碍位错运动,导致最大的位错滑移临界分切应力,因此镍钛样品表现出最高的屈服强度。 相似文献
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The microstructural evolution of the A2017 semi-solid alloy billets provided with rheocasting and extruding/extending forming by shearing-cooling-rolling(SCR) technology during reheating in semi-solid state was investigated. The microstructural differences and their generation causes for both billets were also analyzed. The results show that during reheating, the grains of rheocasting billets grow up and spheroidize gradually with the prolongation of isothermal holding time, the eutectic liquid phase at low melting point forms mainly among the grains. However, the grains of the extruding/extending forming billets grow up abnormally through grain coalescence in the initial stage of the reheating, the entrapment of large amount of liquid within grains occurs, and the grain sizes in the reheating billets are coarse and inhomogeneous. Compared with extruding/extending forming billets, rheocasting billets have smaller and uniform grains in reheating microstructure and can rapidly form liquid phase among grains. Therefore, rheocasting billets are more suitable for the semi-solid forming than the extruding/extending forming billets. 相似文献
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The aging characteristics of as-quenched microstructures of ZA-27 alloy and SiCp/ZA-27 composite(ZMCp) were investigated using SEM, EDS and TEM. The structure, morphology and size of sub-grains in primary dendrite in ZMCp continuously change during aging process. Little tiny spherical Zn-rich η phase distributes in the dendrite. Amount of transitional a' phase, well coherent with equilibrium αf phase, in SiCp-neighboring dendrite edge zone is less than that in dendrite center zone. Both eutectic and peritectic β phase transform into lamellar a and η phases, obeying [2113] η//[ 110]α, and (002)α//(1 1 01)η In the like-eutecticum of ZMCp, less amount of β phase and decomposition products are found. The size of α phase decomposed from peritectic β phase in ZMCp is obviously larger than that in the monolithic alloy. The lamella decomposition of β phase beside SiCp is evidently more rapid than that in the alloy. SiC particulates strongly accelerate neighboring β phase decomposition in aging process. 相似文献
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Z.M. Zhang)* J.C. Wang) H.Z. Liu) X.F. Guo) ) School of Materials Science & Engineering Xi''''an University of Technology Xi''''an China ) State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi''''an China 《金属学报(英文版)》2006,19(5):379-384
1. Introduction Because ZA27 alloy possesses excellent mechanical properties and high damping capacities, it is widely used in industries. ZA27 alloy has good castability and can be easily cast into various castings by permanent mold casting. The solidification of ZA27 alloy in the permanent mold can be considered to be a nonequilibrium process, and thus the supersaturated aluminum-rich ! phase and unstable copper-rich phase may also be found in the solidified ingot. Those nonequilibrium pha… 相似文献