X.F. Zhang
材料科学技术（英文）
Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations. Usually, decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased. However, low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study. By direct tracking of the morphological evolution during phase transformation, it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite, whereas small austenite grain size leads to grain boundary nucleation of bainite. This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.
关键词:
In situ observation
X.F. Zhang
材料科学技术（英文）
Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prestrain, Bi interfacial segregation to the anode, a clear indication of electromigration damage in SnBi solder interconnect, was effectively prevented. Such an inhibiting effect is apparently contrary to the common notion that dislocations often act as fast diffusion paths. It is suggested that the dislocations introduced by plastic prestraining acted as sinks for vacancies in the early stage of the electromigration process, but as the vacancies accumulated at the dislocations, climb of those dislocations prompted recovery of the deformed samples under
current stressing, greatly decreasing the density of dislocation and vacancy in the solder, leading to slower diffusion of Bi atoms.
关键词:
Electromigration
X.F. Zhang
,
D.J. Wang
,
G. Xie
金属学报(英文版)
The Al/fly ash composites are fabricated by liquid reactive sintering P/M process withfly ash particles as intensifying phases. The reactivity and newly formed phases dur-ing liquid sintering process have been analyzed by combing Thermochemical data basecalculation and XRD characterization. The results show that some of constituents infly ash have reacted with liquid aluminum so that the elemental Si, Fe, Ti as well assome amount of intermetallic compounds occur. The properties of aluminum/fly ashcomposites have been improved. With the fraction of fly ash increase, the compositedensity decreases; the hardness and the modulus of the composite increases, and thecomposite wear resistance are significantly increased. The fly ash reinforced compos-ires represent a sort of low cost product with possible widespread applications in theautomotive, small engine, and electromechanical machinery sectors.
关键词:
aluminum/fly ash composite
,
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