李福安
,
松林
,
包黎红
,
哈斯朝鲁
,
特古斯
,
黄焦宏
金属学报
使用电弧熔炼法制备了LaFe11.9-xCoxSi1.1B0.2( x=0.7, 0.8, 0.9)系列化合物。室温下XRD分析表明该系列化合物所成的相基本上都是NaZn13型立方结构单相，除了含有极少量的α-Fe杂相，空间群为Fm-3c。晶格常数(a/Å)随着Co含量的增加而增大，分别为11.487、11.496、11.498 Å；磁性测量发现该系列化合物的居里温度在室温附近，并且也随着Co含量的增加而增加，分别为270,290,300 K。在外场变化ΔB=1.5 T 时，该系列化合物的最大磁熵变达到金属Gd的两倍，相对制冷能力与金属Gd的相对制冷能力基本相同。
关键词:
磁熵变
,
Intermetallic compound
,
Relative cooling power
Huaqing LI
,
Shuisheng XIE
,
Xujun MI
,
Pengyue WU
材料科学技术（英）
Phases of Cu-(0.4%–2.0%) Cr-(0.05%–0.16%) Zr alloys were analyzed in both as cast and deformed state. Solute-rich clusters of Cr, which was supposed to form during aging treatment, were observed in as cast state; along with the morphology character, corresponding preferential orientation of Cr phase in as cast state was also investigated. Precipitates were observed to distribute in the matrix with a bimodal distribution, viz. coarse precipitates with dimension larger than several hundred nanometers and fine precipitates with size of 2– 10 nm. Three types of intermetallics, the common compound of Cu51Zr14, correspondingly infrequent Cu5Zr and rare Cu8Zr3, were characterized in different samples.
关键词:
Cu-Cr-Zr alloy
,
null
,
null
,
null
Hongtao CHEN
材料科学技术（英）
The influence of thermal cycling on the microstructure and joint strength of Sn3.5Ag0.75Cu (SAC) and Sn63Pb37 (SnPb) solder joints was investigated. SAC and SnPb solder balls were soldered on 0.1 and 0.9 μm Au finished metallization, respectively. After 1000 thermal cycles between -40℃ and 125℃, a very thin intermetallic compound (IMC) layer containing Au, Sn, Ni, and Cu formed at the interface between SAC solder joints and underneath metallization with 0.1 μm Au finish, and (Au, Ni, Cu)Sn4 and a very thin Au-Sn-Ni-Cu IMC layer formed between SAC solder joints and underneath metallization with 0.9 μm Au finish. For SnPb solder joints with 0.1 μm Au finish, a thin (Ni, Cu, Au)3Sn4 IMC layer and a Pb-rich layer formed below and above the (Au, Ni)Sn4 IMC, respectively. Cu diffused through Ni layer and was involved into the IMC formation process. Similar interfacial microstructure was also found for SnPb solder joints with 0.9 μm Au finish. The results of shear test show that the shear strength of SAC solder joints is consistently higher than that of SnPb eutectic solder joints during thermal cycling.
关键词:
Sn3.5Ag0.75Cu
,
solder
,
joint
,
Au
,
metallizat
D. Chen
,
G.X. Li
,
D.L. Zhang
,
T. Gao
金属学报(英文版)
The equilibrium structures and electronic structure of LaNi 5-x Ga x (x=0, 0.5, 1.0) compounds have been investigated by all-electron calculations. Based on the full geometry optimization, the densities of states and electron densities of LaNi 5-x Ga x are plotted and analyzed. It is clear that the substitution of Ga at the Ni site leads to a progressive filling of the Ni-d bands, the ionic interaction between Ni and Ni, with Ga plays a dominant role in the stability of LaNi 5-x Ga x compounds. The smaller the shift of E F toward higher energy region, the more stable thecompounds will be. The increased contribution of the Ni-d-Ga-d interactions near E F and the low energy metal-gallium bonding bands indicate that the compounds become more stable. The results are compared with experimental data and discussed in light
of previous studies.
关键词:
FLAPW and GGA
,
null
,
null
,
null
G.S.Cho
,
J.H.Yang
,
K.H.Choe
,
K.W.Lee
,
A.Ikenaga
材料科学技术（英）
We focused on the surface reinforcement of ligth weight casting alloys with Ni-Al intermetallic compounds by in-situ combustion reaction to improve the surface properties of non-ferrous casting components. In our previous works, green compact of elemental Ni and Al powders were reacted to form Ni3Al intermetallic compound by SHS (Self-propagating high temperature synthesis) reaction with the heat of molten Al alloy and simultaneously bonded with Al casting alloy. But some defects such as tiny cracks and porosities were remained in the reacted compact. So we applied pressure to prevent thermal cracks and fill up the pores with liquid Al alloy by squeeze casting process. The compressed Al alloy bonded with the Ni3Al intermetallic compound was sectioned and observed by optical microscopy and scanning electron microscopy (SEM). The stoichiometric compositions of the intermetallics formed around the bonded interface and in the reacted compact were identified by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). Si rich layer was formed on the Al alloy side near the bonded interface by the sequential solidification of Al alloy. The porosities observed in the reacted Ni3Al compact were filled up with the liquid Al alloy. The Si particles from the molten Al alloy were detected in the pores of reacted Ni3Al intermetallic compact. The Al casting alloy and Ni3Al intermetallic compound were joined very soundly by applying pressure to the liquid Al alloy.
关键词:
Joining
,
null
,
null
,
null
,
null
