當(dāng)晶體發(fā)生變形時(shí),，有兩個(gè)主要機(jī)制在發(fā)揮作用：普通脫位彈性和形變孿晶,。雖然前者已知依賴(lài)于晶體尺寸,、因而在納米尺度影響樣本強(qiáng)度，但后者的尺寸依賴(lài)性迄今尚未被研究過(guò),。
現(xiàn)在,，Ju Li及其同事利用微壓縮和納米壓痕實(shí)驗(yàn)發(fā)現(xiàn),，形變孿晶在尺寸小于一微米的晶體中被完全抑制，從而使得普通脫位彈性成為惟一形變模式,。這也許是因?yàn)樾巫儗\晶是一個(gè)集體現(xiàn)象,，對(duì)于小尺寸晶體不能發(fā)生。這一發(fā)現(xiàn)為在微觀尺度操縱材料機(jī)械性質(zhì)的新方法鋪平了道路,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 463, 335-338 (21 January 2010) | doi:10.1038/nature08692
Strong crystal size effect on deformation twinning
Qian Yu1, Zhi-Wei Shan1,2, Ju Li3, Xiaoxu Huang4, Lin Xiao1, Jun Sun1 & Evan Ma1,5
1 Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049, China
2 Hysitron Incorporated, 10025 Valley View Road, Minneapolis, Minnesota 55344, USA
3 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
4 Danish-Chinese Center for Nanometals, Materials Research Division, Ris? National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde, Denmark
5 Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
Deformation twinning1, 2, 3, 4, 5, 6 in crystals is a highly coherent inelastic shearing process that controls the mechanical behaviour of many materials, but its origin and spatio-temporal features are shrouded in mystery. Using micro-compression and in situ nano-compression experiments, here we find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal7, 8, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation plasticity. Accompanying the transition in deformation mechanism, the maximum flow stress of the submicrometre-sized pillars was observed to saturate at a value close to titanium’s ideal strength9, 10. We develop a ‘stimulated slip’ model to explain the strong size dependence of deformation twinning. The sample size in transition is relatively large and easily accessible in experiments, making our understanding of size dependence11, 12, 13, 14, 15, 16, 17 relevant for applications.
