J.C. Wang
,
Z.M. Zhang
,
Y.L. Lu
,
G.S. Song and G.C. Yang (State Key Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China)
金属学报(英文版)
To improve the damping capacities of metals and alloys, the microstructures and damping capacities of ZA27 alloy modified by Zr were studied, and the damping capacities at room tempemture were measured by using cantilever beam techniques. The experiment results show that Zr can refine the Al-rich primary phase and improve the damping Capacities saliently. Compared with the un-modified one, the damping capacity of ZA27 alloy modified by 0.3wt%Zr received 90 percent increment. The high damping capacities are attributed primarily to grain ablement and the increasing of phase interfaces.
关键词:
ZA27 alloy
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null
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null
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null
Tijun CHEN
,
Yuan HAO
,
Jun SUN
材料科学技术（英文）
The investigations were performed into the formation processes of liquid pools entrapped within solid grains of three ZA27 alloys, produced respectively by either grain refinement, or traditional permanent casting or mechanical stirring, during partial remelting at semisolid temperature of 460°C. The results show that the rapid coalescence of primary grains due to merging of secondary arms during the initial stage of partial remelting is the main cause for the formation of the entrapped liquid pools. This coalescence resulted in that a high quality of eutectics, especially the h phase, was entrapped within the grains, and then remelted to form liquid pools during the subsequent heating. In addition, the growth of the h phase decomposed from the primary a' phase and b phase and the subsequent remelting is another cause for the refined and permanent mould casting alloys. Furthermore, the agglomeration of the solid grains also resulted in the entrapment of liquid in the interior of grains.
关键词:
Thixoforming
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null
,
null
,
null
null
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null
,
null
,
null
金属学报(英文版)
ZA27 alloy was prepared by casting with permanent mold and then annealed at 250℃ for 1-4h. The damping capacity of the alloy was measured using a testing apparatus based on the cantilever beam technique. It was found that the as-cast ZA27 alloy possesses high damping capacity with the value of 1.3 × 10-3 at 320Hz. After annealed at 250℃ for 1h, the damping capacity decreases to 1.1 × 10-3 and then remains constant even when the annealing time is increased to 4h. The microstructure of the as-cast ZA27 alloy consists of large dendrites of Al-rich primary α-phases, eutectoid (α + η) and nonequilibrium eutectic phases (α + η + ε). After annealing at 250℃ for 1h, the ε phase disappears due to dissolution into the matrix, and the spacing between the flakes of eutectoid increases. The further increase in the annealing time has little effect on the spacing. The damping mechanism of the alloy was discussed considering the thermoelastic damping and defect damping. The value of thermoelastic damping accounts only for 7%-8% in the overall damping in cantilever beam damping measurements and the damping capacity of the ZA27 alloy came mainly from defect damping.
关键词:
damping capacity
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null
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null
李红英
,
刘洋
,
胡继东
,
武岳
材料热处理学报
采用扫描电镜（SEM）、X射线衍射（XRD）和力学性能测试等手段研究了固溶处理对ZA27合金组织和性能的影响。在300～380℃范围,合金经不同温度固溶处理1 h,水淬后进行相同的时效（160℃×8 h）处理。分析了在不同温度固溶处理的淬火态和时效态合金的显微组织及力学性能。结果表明,在365℃固溶处理能够使溶质原子充分溶入基体,时效析出相数量多、尺寸小、分布均匀,时效强化效果最好。ZA27合金的优选固溶工艺为365℃×1 h。
关键词:
ZA27合金
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固溶温度
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组织
,
性能
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析出相
刘占勇
,
左孝青
,
钟子龙
,
李威威
材料工程
doi:10.11868/j.issn.1001-4381.2015.000920
通过与常规铸造方法的比较,研究半固态触变挤压对ZA27合金变质、热处理组织和力学性能的影响.结果表明:半固态挤压态合金的密度较铸态合金提高了3%,合金经Sc变质或者半固态挤压都获得了细小而均匀的近似球状组织,而Sc变质结合半固态挤压的球状组织具有最高的圆整度;经T6热处理的半固态挤压合金由细小的初生α相和共析(α+η)组织组成,说明半固态挤压可促进ε相溶解、减少三元共晶(β+η+ε)组织的含量.力学性能测试表明,ZA27合金经半固态挤压+Sc变质+T6热处理后其抗拉强度,伸长率和布氏硬度分别达到586.01MPa,17.57%及171HB.
关键词:
ZA27合金
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Sc变质
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半固态触变挤压
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微观组织
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力学性能
邱谨
,
李元东
,
李明
,
张继渊
,
管仁国
,
陈体军
中国有色金属学报
采用自孕育法制备ZA27半固态浆料,研究流变压铸成形过程中的显微组织及凝固行为.结果表明:ZA27半固态浆料在480℃等温保温3 min,能够制备出细小、圆整、分布均匀的初生α(Al)晶粒,平均晶粒尺寸52.32 μm.浆料在成形过程中发生液相偏析,在受力较大部位,二次颗粒长成“蠕虫状”.剩余液相在铸件不同部位的凝固方式不同,但都没有粗大的树枝晶存在.在冷却速率较小的部位,二次凝固方式主要为依附初生晶粒生长,在共晶组织中有包晶β相析出.在冷却速率较大部位主要为形核凝固,二次晶粒数目多,共晶组织细小.二次晶粒既能够以富Zn的α(Al)相形核,也可以直接以β相形核生长.Cu富集在共品η相中.
关键词:
自孕育法
,
二次凝固
,
半固态
,
包晶
,
共晶
,
ZA27合金
