Xing LU
,
Zuoxiang QIN
,
Yansheng ZHANG
,
Xingyu WANG
,
Fengxian LI
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英）
The effect of C content (0.014 similar to 0.39 wt pet) on the paramagnetic-antiferromagnetic transition and gamma --> epsilon martensitic transformation of Fe-24Mn alloys has been investigated by the resistivity, dilation, tensile properties measurement and microstructure examination. The results have shown that C decreases T-N, increases the thermal expansion coefficients both above and below the Tu, increases the resistivity above the TN and antiferromagnetic scattering resistivity below TN. It strongly depresses the gamma --> epsilon martensitic transformation and reduces the Ms of Fe-24Mn alloys. Moreover, it increases the lattice parameter of austenite, enhances the tensile ductility, but almost does not affect the tensile strength. With increasing C content from 0.014 to 0.19 wt pet, the yield strength of Fe-24Mn alloy decreases obviously arising from the decreasing of preexisting epsilon martensite, but it increases from 0.19 to 0.39 wt pet C due to the solution hardening of C.
关键词:
Wei JIN
,
Mingzhou GAO
,
Rui YANG
,
Zhuangqi HU
材料科学技术（英）
The recovery strain, stress and transformation temperature of different pre-strained specimens of Ti44Ni47Nb9 were investigated by tensile test and electrical resistance measurement. The results indicated that pre-strain increases the reverse martensitic transformation temperature (A ' (s)) and hysteresis (A(s) - M-s). The recovery strain and stress are higher if the specimens are pre-strained between M-s and A(s) temperature than outside this temperature range. There exists an optimal pre-strain value, about 10%, at which the specimen exhibits maximum recovery strain and stress.
关键词:
Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英）
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
,
null
,
null
Ping PENG
,
Caixing ZHENG
,
Shaochang HAN
,
Zhaohui JIN
,
Rui YANG
,
Zhuangqi HU
材料科学技术（英）
The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Al interface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was found that the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand, less than -0.6% negative lattice misfit can promote the binding strength of γ/ interface. On the other hand, the total bonding strength ofγ/ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must be carefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structural stability ofγ/ interface when one designs a new Ni-base single crystal superalloy.
关键词:
γ/ interface
,
null
,
null
,
null
Jia ZHANG
,
Wensheng SUN
,
Mingxiu QUAN
,
Zhuangqi HU
材料科学技术（英）
Microstructure and subsequent phase transformations on heating of the melt-spun Nd85Al15 alloy have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The melt-spun Nd85Al15 alloy shows two-stage transformation processes as follows: amorphous+72 nm supersaturated bcc-Nd(Al) solid solution→7 nm omega-like phase→AlNd3+hexagonal Nd. The activation energies for the first and second transformation were found to be 100 kJ/mol and 188 kJ/mol, respectively. The formation mechanism of nanoscale omega-like phase is discussed.
关键词:
Melt-spun Nd85Al15 alloy
,
null
,
null
Fengxiang QIN
,
Haifeng ZHANG
,
Aimin WANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英）
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）
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
,
null
,
null
Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英）
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
,
null
,
null
,
null
Qingsheng ZHANG
,
Shiding WU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英）
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
,
null
,
null
Xianfeng PAN
,
Haifeng ZHANG
,
Aimin WANG
,
Bingzhe DING
,
Keqiang QIU
,
Zhuangqi HU
材料科学技术（英）
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:
