原文由 NeoSoulXD 於 2008-1-4 02:03 發表
小弟有大略看過和翻譯了..但是真的是完全搞不懂...
這是麻省理工學院的材料系的課外閱讀參考文獻
麻煩大家了~
第一篇
Abstract
Although it is well known that thin metal films exhibit mechanical properties very different from those of their bulk counterparts, knowledge of the underlying mechanisms is incomplete. In this study of plasticity in unpassivated Cu thin
films, thermal cycling experiments were performed using both wafer curvature equipment and in situ transmission electron
microscopy. It was found that the room temperature flow stress increases with decreasing film thickness, but exhibits a plateau for films 400 nm and thinner. It was also observed that a new type of dislocation motion becomes operative in this plateau region. The unexpected glide of dislocations on a (1 1 1) plane parallel to the film/substrate interface, which we have termed parallel glide, completely replaces threading dislocation motion as the dominant mechanism in films 200 nm and thinner. Parallel glide appears to be a consequence of constrained diffusional creep, which involves a diffusive exchange of atoms between the unpassivated film surface and the grain boundaries at high temperatures. This process is reversible during heating versus cooling, and is highly repeatable from one thermal cycle to the next. The observed populations of parallel glide dislocations fully account for the plastic strain measured in wafer curvature experiments.
第二篇
We use massively parallel molecular dynamics simulations of polycrystal plasticity to elucidate the intricate dislocation dynamics that evolves during the process of deformation of columnar nanocrystalline Al microstructures of grain size between 30 and 100 nm. We analyze in detail the mechanisms of dislocation-dislocation and dislocation-twin boundary reactions that take place under sufficiently high stress. These reactions are shown to lead to the formation of complex twin networks, i.e. structures of coherent twin boundaries connected by stair-rod dislocations. Consistent with recent experimental observations, these twin networks may cause dislocation pile-ups and thus give rise to strain hardening
第三篇
Complementary large scale molecular-dynamics simulations and experiments have been carried out to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe{110}, {100}, and {111}. The defect formation and motion causes the complex mechanisms of plastic and elastic deformation which is reflected in the pileup patterns. The experimental results show distinct patterns of pileup material which are dependent on the individual crystal faces and
the superposition of the stress field of the indenter. The highest pileup around the indenter hole occurs on the {100} surface and the shallowest on {111}. The least symmetric surface is {110} which produces an experimental pileup pattern displaying only twofold symmetry with the axially symmetric indenter. The pyramidal indenter produces an asymmetric pattern which changes as the crystal is rotated with respect to the tip but repeats with threefold rotational symmetry.
Material displacement occurs primarily in planes of the {110} family. Pileup is formed by cross slip between planes of the same family which intersect in 〈111〉 directions. For the {110} surface, dislocation loops propagate in the four in-plane 〈111〉 directions and the two inclined 〈111〉 directions. The loops that propagate in the in-plane directions are terminated by edge dislocations at the surface. These transport material away from the tip but cannot produce pileup. The
loops that propagate in the inclined direction cross slip and cause the observed pileup. The {100} surface has fourfold rotational symmetry and all the 〈111〉 directions are inclined. The dislocation loops propagate in these directions and cross slip readily occurs, leading to a large pileup. The {111} face shows the least pileup which is more spread out over the surface. In this case the dislocation loops propagate in shallow slip planes and do not readily cross slip. Experimentally determined force-depth curves show distinct “pop-ins” which correspond to the formation of dislocations. The contact pressure (nanohardness) is not a constant and increases with decreasing indentation depth. It
also changes with crystal face. Calculated force-depth curves match the experimental trend but give estimates of the nanohardness and Young’s modulus higher than those values experimentally determined.
我用Dr.eye 8.0 pro幫妳翻譯的結果如下:如果不準請見諒
第一篇
摘要
雖然眾所周知薄的金屬電影展覽非常不同於他們的體積極相似的物的的機械特性，但是基礎的機製的知識是不完全的。 在在薄unpassivated銅裡的塑性的這項研究過程中
騎單車的電影，上升熱氣團實驗被使用維夫餅乾彎曲設備和在原處輸送電子作秀
顯微術。 發現室溫流動重音與減少電影濃度一起增加，但是展覽給電影的一高原和瘦的400納米。 也觀察一新型混亂運動在這個高原地區生效。 在(1 1 1)上的混亂的想不到的滑動 我們已經稱平行的滑動的與電影/ 底層界面平行的飛機， 完全在電影接替穿過混亂運動充當聳立機製和瘦的200納米。 平行滑動看起來是一個強製的diffusional的結果爬去， 在高溫下與一次在unpassivated 電影表面和糧食邊界之間的原子的散播的交換有關。 這個過程在加熱與冷卻期間是可逆的，並且從一個熱循環到下一個非常重複。 平行的滑動混亂的被觀察的人口完全解釋在維夫餅乾彎曲實驗裡測量的塑性應變。
第二篇
我們大量地使用多晶體塑性的平行的分子力學類比闡明逐步形成的錯綜複雜的混亂力學， 在在30 和100納米之間的粒度的專欄的nanocrystalline艾爾微視架構的變形的過程期間。 我們詳細分析混亂混亂的機製和在足夠高的壓力下發生的混亂雙晶界回應。 這些回應被顯示導致複雜的雙胞胎網路的形成， 即 前後一致的雙晶界的架構因為樓梯杆混亂被連結。 和新近的實驗報告一致，這些雙胞胎網路可能引起混亂堆積如山，因此引起應變硬化
第三篇
補充的大規模分子力學的類比和實驗已經被進行在Fe單晶裡確定nanoindentation 過程的原子的機製 {110 },{100 },並且 {111 }. 缺陷形成和運動引起被反映在pileup 圖案上的塑膠和彈性變形的複雜的機製。 實驗結果顯示倚賴個別的水晶表面的pileup 材料的清楚的模型和
indenter的壓力領域的重疊。 在周遭那些最高的pileup那些indenter 挖洞發生對 {100 } 表面和最淺的在上 {111 }. 最不勻稱表面是 {110 } 生產一種實驗pileup 圖案(只展示用沿軸方向勻稱的indenter的雙重的對稱性)。 金字塔的indenter 生產改變的一種非對稱的圖案，當水晶被關於訊息旋轉時，但是有三倍的旋轉的對稱性重複。
物質替代發生主要在方面飛機 {110 } 家庭。 Pileup 煩惱成立在相同的家庭的飛機之間滑過在q111 r 指示的相交。 為 {110 } 表面，位錯環用4 個在飛機的q111 r 指示和兩個傾斜的q111 r 指示繁殖。 在在飛機的方向傳播的環在表面因為邊緣混亂被結束。 距離訊息的這些種運輸材料但是不能產生pileup。
繁殖的環朝著被傾斜的方向穿過滑過並且引起被觀察的pileup。 {100 } 表面有四褶層旋轉的對稱性和全部q111壓縮比方向傾向於。 位錯環在這些指示內繁殖並且穿過滑過容易發生，導致大的pileup。 {111 } 臉顯示被更在表面上方展開的最小pileup。 這樣的話，位錯環在淺滑動飛機內繁殖並且不容易穿過滑過。 實驗上確定力量深度曲線讓不同的‥pop-ins〃看哪個相當於混亂的形成。 聯繫壓力(nanohardness) 不是常量並且有減少凹口深度增加。 它
此外隨水晶表面而變。 計算力量深度曲線比得上實驗趨勢但是給nanohardness 和Young s高那些價值實驗上確定的模數的估計。 |
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