X.Y. Pang Z.Q. Liu S.Q. Wang J.K. Shang
材料科学技术（英）
Density functional theory was employed to investigate the bismuth segregation at Cu/Cu3Sn(010) interface. Five initial constructions were introduced by adopting the adhesion energy criterion. Among them, the so-called "between-Cu" construction in which the interface Cu atoms of Cu slab locate along Cu-Cu bond direction in Cu3Sn slab was found to be the most energy-favored at an adhesion energy of 1.96 J/m2. Based on this construction, five possible segregation sites were examined, and the most likely segregation site was determined with adhesion energy as low as 1.06 J/m2, which was almost half of the initial one. Comparing with other sites' adhesion energies, it was concluded that size effect took a large part in embrittlement. The analyses of atomic structure and electronic density revealed that the slabs shifted away from interfaces due to bismuth segregation, and the atoms around Bi atom were pressed away. This calculated work agreed qualitatively with reported experimental results.
关键词:
First-principles calculation
,
segregation
,
Bismuth
,
interface
,
SnBi solder.
Zhuang Li Di Wu
材料科学技术（英）
The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe. The experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels. The conventional austenitic stainless steel 1Cr18Ni9Ti (steel A) and the free cutting austenitic stainless steel (steel B) were prepared. The results have shown that machinable inclusions were composed of MnS and CuO, and they might be also Ti4C2S2. The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis (EPMA), which might be one of the most important factors to improve the machinability of austenitic stainless steels. The cutting forces for steel B were lower than those of steel A at various cutting speeds; the abrasion depth of theflank of the tool for steel B was less than that of the steel A under the same cutting conditions. The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives, such as S, Cu and Bi. Ultimate tensile, yield strength, and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.
关键词:
Austenitic stainless steel
,
free-cutting additives
,
bismuth
,
machining characteristics
,
the mechanical properties.
Zhuang Li Di Wu
材料科学技术（英）
The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe. The experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels. The conventional austenitic stainless steel 1Cr18Ni9Ti (steel A) and the free cutting austenitic stainless steel (steel B) were prepared. The results have shown that machinable inclusions were composed of MnS and CuO, and they might be also Ti4C2S2. The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis (EPMA), which might be one of the most important factors to improve the machinability of austenitic stainless steels. The cutting forces for steel B were lower than those of steel A at various cutting speeds; the abrasion depth of theflank of the tool for steel B was less than that of the steel A under the same cutting conditions. The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives, such as S, Cu and Bi. Ultimate tensile, yield strength, and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.
关键词:
Austenitic stainless steel
,
free-cutting additives
,
bismuth
,
machining characteristics
,
the mechanical properties.
