Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The nature and growth of the interaction layers between solid Nb and liquid Al has been studied by carrying out the tests on Nb(s)-Al(l) and Nb(s)-Al(l)-Ni(s) reaction couples isothermally reacted between 700°C and 900°C for different time intervals. It has been found that the interaction layer between Nb and Al contains two parts: a thin continuous layer of NbAl3 adjacent to the Nb surface and a two-phase zone constituted of NbAl3 particles dispersed in an Al matrix. Although the nature and growth of interaction layers follows the four-stage mechanism, a typical cruciform pattern does not occur in Nb(s)-Al(l) reaction couples. However, a cruciform pattern was observed in Nb(s)-Al(l)-Ni(s) reaction couples. The movement of NbAl3 particles is important to the production of cruciform pattern in the reaction couples.
关键词:
Wetting
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null
,
null
Fengxiang QIN
,
Haifeng ZHANG
,
Aimin WANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The effect of Pd addition on the glass-forming ability and thermal stability of the Zr55Al10Cu30Ni5-xPdx (x=0, 1, 3, 5 at. pct) alloys upon copper-mold casting has been investigated. The structure, thermal stability and microstructure were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. It was identified that a new bulk amorphous alloy with the larger supercooled liquid region △Tx of 100 K is obtained with substituting Ni by 1 at. pct Pd. However, the addition of 3 at. pct Pd causes a little increase of thermal stability and an evident decrease of the GFA. The full substitution Ni by 5 at. Pct Pd induces the thermal stability and GFA to decrease simultaneously. It indicates that the thermal stability increases and the GFA decreases with the increasing of Pd content.
关键词:
Bulk Amorphous Alloy
,
null
,
null
Jia ZHANG
,
Keqiang QIU
,
Aimin WANG
,
Haifeng ZHANG
,
Mingxiu QUAN
,
Zhuangqi HU
材料科学技术（英文）
The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2～5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffraction, transmission electron microscope and electron probe microanalysis. Experimental results show that the pressure has a great influence on the solidification microstructure of the Mg65Cu25Y10. At ambient pressure, the solidification products are Mg2(Cu,Y) and a very small amount of Y2O3 inclusion. As the pressure is above 2 GPa, a new Cu2(Y,Mg) phase appears, while Y2O3 is not observed at the pressure of 3, 4 and 5 GPa. When the pressure increases from 2 GPa to 5 GPa, the grain sizes of Mg2(Cu,Y) and Cu2(Y,Mg) decrease from 125, 96 nm to 80, 7 nm, respectively. The mechanisms for the effects of the pressure on the phase evolution and microstructure during solidification process of Mg65Cu25Y10 alloy have been discussed.
关键词:
Mg65Cu25Y10 alloy
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null
,
null
Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The wetting behavior of molten Bi on polycrystalline Cu substrate and single crystal Cu substrate was studied by the sessile drop method in the temperature range from 673 to 873K. At low temperature the wetting behaviors of molten Bi on both types of Cu substrate were similar. However, at high temperature, the equilibrium contact angle of polycrystalline Cu substrate was lower than that of single crystal Cu substrate, because the preferred dissolution of grain boundaries leads to a smaller liquid/solid interfacial energy for polycrystalline Cu substrate. The formation mechanism of arrow-shaped Cu grains at the Bi/single crystal Cu interface is also discussed.
关键词:
Wettability
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null
,
null
,
null
Qingsheng ZHANG
,
Shiding WU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition were investigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiation occurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallite near the surface. The average striation spacing on amorphous area is much larger than that on the crystallite. Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformation condition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared on the surface of specimen with fine crystallites under cyclic loading.
关键词:
Bulk amorphous alloy
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null
,
null
Xianfeng PAN
,
Haifeng ZHANG
,
Aimin WANG
,
Bingzhe DING
,
Keqiang QIU
,
Zhuangqi HU
材料科学技术（英文）
This paper reviewed the trend and development of semi-solid metal technique. The processes and mechanisms for producing slurry of SSM and its industrial applications have been summarized and discussed. Discussions on the basic rheological theory are presented for more applications. Further consideration of the development and application of SSM technique is also proposed.
关键词:
Hao WANG
,
Xiaoping SONG
,
Xiangdong YAO
,
Haifeng ZHANG
,
Zhuangqi HU
材料科学技术（英文）
The crystallization behavior and crystallization kinetics of (Cu60Zr30Ti10)99Sn1 bulk metallic glass was studied by X-ray diffractometry and differential scanning calorimetry. It was found that a two-stage crystallization took place during continuous heating of the bulk metallic glass. Both the glass transition temperature Tg and the crystallization peak temperatures Tp displayed a strong dependence on the heating rate. The activation energy was determined by the Kissinger analysis method. In the first-stage of the crystallization, the transformation of the bulk metallic glass to the phase one occurred with an activation energy of 386 kJ/mol; in the second-stage, the formation of the phase two took place at an activation energy of 381 kJ/mol.
关键词:
Bulk metallic glasses
,
null
,
null
Keqiang QIU
,
Qingsheng ZHANG
,
Aimin WANG
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85mm×35mm×4mm and a complicated plate were fabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper as raw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence on the oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding time resulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallic glass plates are higher than that reported in the literature and crystallization temperature is lower for the one with higher oxygen content at the same heating rate. The extension of the undercooled liquid region ΔTX reaching about 87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct for the one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significant influence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlation between high glass forming ability and large ΔTX is only valid for a well-defined low oxygen concentration or has to be reconsidered by incorporating oxygen as an additional alloying element.
关键词:
Zr-base amorphous alloy
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null
,
null
Jianjun LIU
,
Keqiang QIU
,
Aimin WANG
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different under different pressure. At ambient pressure, the crystallization products consisted of NiZr2 and CuZr2, while at pressure of 1 GPa and 3 GPa, the alloys crystallized into NiZr2 and Cu10Zr7, respectively. The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 GPa. DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.
关键词:
Bulk metallic glan
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null
,
null
