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1.
用熔融玻璃净化与循环过热相结合的方法,研究了亚偏晶Cu-25%Pb合金,Cu-37.4%Pb偏晶合金和过偏晶Cu-40%Pb(质量分数)合金过冷熔体凝固行为和凝固组织的演化规律,以及Cu-37.4%Pb偏晶合金的过冷度对磨损率的影响.研究表明:在过冷亚偏晶Cu 25%Pb合金熔体凝固过程中先形成α(Cu)初生相,随着过冷度的增大,凝固组织经历粗大枝晶重熔形成的细化枝晶向准球状晶粒演化的过程;在过冷Cu-37.4%Pb偏晶合金熔体凝固过程中初生相为L2相,当过冷度在20~150 K区间时,得到第二相S(Pb)弥散在α(Cu)枝晶间的凝固组织,并且在该过冷区间内随着过冷度的增加,材料的磨损率也逐渐降低;在过冷过偏晶Cu-40%Pb合金熔体凝固过程中初生相为L2相,在过冷度区间42~80 K时,得到以偏晶胞形式分布的凝固组织. 相似文献
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本文通过净化法使 Ni-32.5wt-%Sn 共晶合金液获得深过冷,对该合金液在不同过冷条件下的凝固机制和组织进行了研究。结果表明:当过冷度小于约10K 时,该合金液凝固生成 Ni_3Sn相和 Ni(α)相层片共晶。在深过冷条件下,由于 Ni_3Sn 枝晶的自由生长速度远大于 Ni(α)枝晶的自由生长速度,再辉过程中,Ni_3Sn 相和 Ni(α)相不能以匹配方式生长,而由 Ni_3Sn 相作为领先相以枝晶簇方式生长。再辉过程中形成的枝晶簇,其内部 Ni_3Sn 枝晶进一步熔断粗化及 Ni(α)相在Ni_3Sn 枝晶间形成生长,最后形成非规则共晶组织。当过冷度小于130K 时,再辉之后,枝晶簇间存留有较大体积的成分仍为 Ni-32.5wt-%Sn 的合金液,这部分合金液在共晶平台阶段以层片共晶方式凝固,所以试样内部的组织由非规则共晶区和层片共晶区组成。 相似文献
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深过冷Ni80.3B19.7合金的再辉和非规则共晶的形成 总被引:3,自引:0,他引:3
采用熔融玻璃净化结合气体保护的方法,使Ni80 3B19 7过共晶合金获得了407 K的大过冷度,研究了其在不同过冷度下快速凝固过程中的再辉行为.结果表明,Ni80 3B19.7过共晶合金在0~112 K过冷度范围内无明显再辉,在112~323 K过冷度范围内,其再辉曲线表现为两个再辉峰,而在323~407 K过冷度范围内,其再辉曲线为一个再辉峰.初生固相含量的随着过冷度的增大而增大,导致一次再辉度随着过冷度的增大而增大.深过冷Ni80 3B19.7合金凝固组织中非规则共晶的形成,归因于共晶两相在快速凝固阶段以自由枝晶的形式进行的非耦合生长和再辉后的慢速凝固阶段两相枝晶所发生的形态上的转变. 相似文献
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制备了定向凝固Cu-1.0%Cr亚共晶自生复合材料,研究了初生α相生长对共晶生长的影响机制,探讨了亚共晶合金中共晶的生长规律.研究结果表明,Cu-1.0%Cr合金定向凝固时,在初生α相间生长的共晶受到初生相生长的影响,在热场不定向和生长空间受限的双重作用下,共晶无定向地杂乱生长.初生α相的生长引起枝晶间液相溶质分布的变化,随着凝固速度的增大,初生α枝晶间液相溶质的浓度分布趋于平缓,成分趋近于CE.Cu-1.0%Cr合金在快速凝固条件下,初生α相生长改变了共晶的生长环境,致使形成非平衡凝固组织--离异共晶. 相似文献
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采用玻璃包覆法(fluxing)提纯和在不同温度下保温,获得了Fe40Ni40P14B6合金熔体的凝固组织,研究了过冷度对凝固组织的影响.结果表明,随着过冷度的增大,Fe40Ni40P14B6的凝固组织从亚共晶转变为共晶组织,晶粒尺寸明显减小.当过冷度超过某一临界值时,合金熔体发生Spinodal分解,形成网状结构的凝固组织并使晶粒显著细化,达到纳米尺度.在深过冷条件下,可获得块体纳米晶凝固组织. 相似文献
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为了消除粗大针状富铁相对Al-Fe合金组织和性能的不良影响,在金属型铸造共晶Al-2?合金中添加了质量分数为0.2%一0.8%的合金元素Mg,利用光学显微镜和电子探针研究了Mg对共晶合金组织以及富铁相形态的影响.研究结果表明:共晶Al-2?合金组织为针状Al3Fe相与(α-Al)相所组成的非规则共晶组织;添加Mg后,合金组织转变为由树枝状初生(α-Al)和枝晶间网状分布共晶体所组成的亚共晶组织,富铁相尺寸显著降低;随着Mg添加量的增加,初生(α-Al)枝晶二次枝晶间距增大,一次枝晶出现熔断. 相似文献
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强脉冲磁场中Al-Cu共晶定向凝固组织的演变 总被引:9,自引:0,他引:9
脉冲磁场作用于Al Cu共晶凝固的界面,研究了定向凝固组织的演变.随着脉冲磁场强度的提高,Al-Cu共晶定向凝固组织经历了由规则柱晶到破碎枝晶、粗化枝晶到重新规则化柱晶三个演化阶段;在重新规则化柱晶试样中,共晶片层间距减小,晶团间富铜相析出明显.将感生电势场与溶质扩散场相耦合,分析了脉冲磁场对凝固界面稳定性的影响,发现强脉冲磁场在金属熔体引起感生电势场效应,在凝固界面前沿诱发具有振荡特征的电致迁移,从而促进晶间扩散和减小成分过冷区域. 相似文献
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Mg对共晶Al-2%Fe合金显微组织的影响 总被引:1,自引:0,他引:1
为了消除粗大针状富铁相对Al-Fe合金组织和性能的不良影响,在金属型铸造共晶Al-2%Fe合金中添加了质量分数为0.2%~0.8%的合金元素Mg,利用光学显微镜和电子探针研究了Mg对共晶合金组织以及富铁相形态的影响.研究结果表明:共晶Al-2%Fe合金组织为针状Al3Fe相与(α-Al)相所组成的非规则共晶组织;添加Mg后,合金组织转变为由树枝状初生(α-Al)和枝晶间网状分布共晶体所组成的亚共晶组织,富铁相尺寸显著降低;随着Mg添加量的增加,初生(α-Al)枝晶二次枝晶间距增大,一次枝晶出现熔断。 相似文献
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超音速电弧喷射Ag—Cu共晶熔滴的快速凝固 总被引:1,自引:0,他引:1
采用超音速电弧喷射雾化制备Ag-40%(原子分数)Cu共晶合金粉末,用X射线衍射、扫描电镜等对其凝固行为进行研究。结果表明:粉末为球形颗粒,粒径分布90%集中在15~60μm之间、平均粒径为35gm;冷却速率在10^5~10^7K/s范围,最大过冷度不小于232K;粉末富Ag相的平均点阵参数为0.401877nm,Cu的平均扩展固溶度为20.15%(原子分数),直径≤50μm时,点阵参数为0.39252nm,Cu的固溶度达到40%(原子分数),凝固组织为单相亚稳固溶体;对快速凝固行为进行了分析讨论。 相似文献
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A method of determining a fixed point using a metal-carbon eutectic from the experimental melting curve, taking into account
the heat expended on heating the ampoule, is proposed.
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Translated from Izmeritel’naya Tekhnika, No. 6, pp. 55–56, June, 2007. 相似文献
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采用实时观测装置和定向凝固系统研究了SCN-Cam(Succinonitrile-wt%Camphor,wt%为质量分数)模型合金的凝固过程.实验结果表明,SCN-23.6%Cam共晶合金在常规条件下形成规则的共晶组织,共晶间距随界面推移速度的增大而减小;加入超声振动时,共晶合金生长出初生相;SCN-21%Cam亚共晶... 相似文献
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An array of lamellar SnSe-SnSe2 structure is obtained by unidirectional solidification, in which SnSe and SnSe2 are, respectively,p andn type semiconductors. Their structural morphology was examined with use of transmission and scanning electron microscopes.
It was found that the ordering of the alternative layers of the phases could be accomplished by a suitable choice of freezing
rates, although several kinds of structural defects such as terminations, misfit lamellae and colony structure were observed.
The mechanisms of these defect formations were considered in terms of the constitutional supercooling. Furthermore, the crystallographic
relationship between the two phases in the solidified state was determined. 相似文献
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Anisotropic elastic constants of Pb-Sn eutectic composites with layered structure have been measured by the pulse-echo method.
The magnitude of the elastic constants was found to vary considerably depending upon the crystallographic directions as well
as the directions relative to the plate-like eutectic constituents. The elastic constants of Pb-Sn eutectic bicrystal were
determined taking thex1 andx3 axes, respectively, as the directions parallel to and normal to the growth direction of the eutectics. The interfacial energy
of Pb-Sn layers was also determined. In addition, the anisotropy of the eutectics was confirmed by resistivity measurements. 相似文献
18.
Effect of isothermal extrusion parameters on mechanical properties of Al-Si eutectic alloy 总被引:1,自引:0,他引:1
Lei DengXinyun Wang Juchen XiaJianjun Li 《Materials Science and Engineering: A》2011,528(21):6504-6509
In this paper, mechanical properties of a deformed Al-Si eutectic alloy processed by isothermal extrusion at temperature from 573 K to 773 K with reduction ratio from 25% to 85% were investigated at ambient temperature. The results showed that a banded structure composed of matrix region and accumulation region of second phase particles was formed and a few cracks were generated in particles and evolved to voids among particles. The tensile strength of test specimens ranged from 250 MPa to 400 MPa and was directly related with temperature from 623 K to 773 K. The elongation of test specimens ranged from 2.8% to 13.1%, and had a peak value at 673 K under each section reduction ratio. A reduction in elongation occurred at section reduction ratio larger than 75% because of particle bands splitting aluminum matrix severely. The effect of temperature on mechanical properties was more significant than that of section reduction ratio. Excellent balance between strength and ductility can be obtained by extrusion at temperature 623-723 K and section reduction ratio 40-70%. 相似文献
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研究了氧化铝/锌合金复合材料的凝固组织及其共晶转变模式,结果表明,在复合材料中纤维与基体间存在致密界面层;合金元素通过适当的化学反应可改善纤维与基体间的结合;在凝固过程中,纤维/基体界面上的硅在共晶本的共生生长过程中起领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变两者组成。 相似文献
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N. A. Parfent’ev 《Measurement Techniques》2007,50(6):662-665
A model to describe the phase transition of a material enclosed in a cylindrical vessel is constructed. Different methods
of determining the phase-transition temperature are compared. The method of determining the temperature at a point situated
at the end of the linear part of the temperature-time graph has the highest accuracy.
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Translated from Izmeritel’naya Tekhnika, No. 6, pp. 53–55, June, 2007. 相似文献