文章信息/Info

Title:

 Intermittent Plastic Flow of Mg-based Metallic Glass under Nanoindentation

作者:

卞西磊; 李潔; 王剛

上海大學(xué)微結(jié)構(gòu)重點實驗室，上海 200444

Author(s):

Bian Xi Lei;  Li Jie;  Wang Gang

Laboratory for Microstructures, Shanghai University, Shanghai 200444, China

關(guān)鍵詞:

非晶合金; 納米壓痕; 應(yīng)變突變; 遍歷處理; 應(yīng)變速率敏感指數(shù); 剪切轉(zhuǎn)變區(qū)

DOI:

10.7502/j.issn.1674-3962.2014.05.02

文獻標志碼:

A

摘要:

鎂基非晶合金通常表現(xiàn)出顯著的宏觀脆性，因此用常規(guī)拉伸、壓縮等方法對該合金的變形行為進行研究具有很大困難。本研究利用具有高時間分辨率和高空間分辨率的納米壓痕技術(shù)觀察了不同加載速率下鎂基非晶合金的鋸齒流變行為。結(jié)果表明，低加載速率促進鋸齒的形成，而高加載速率則抑制鋸齒的形成。其原因是在低加載速率下，單一剪切帶足以耗散外加應(yīng)變；而在高加載速率條件下，由于單一剪切帶不能將應(yīng)變耗散掉，因此更多的剪切帶參與變形。為了進一步解釋這一鋸齒流變行為，本研究對每個鋸齒的應(yīng)變突變進行了統(tǒng)計分析。結(jié)果表明，在不同的加載速率下，小的應(yīng)變突變服從冪律分布，且冪指數(shù)為1.45；而大的應(yīng)變突變則呈現(xiàn)指數(shù)衰減規(guī)律。最后，借助硬度對應(yīng)變速率的敏感性，估算了鎂基非晶合金在納米壓入條件下剪切轉(zhuǎn)變區(qū)的體積。

Abstract:

Mg-based bulk metallic glass under tension test or compression test will show significant brittleness in macroscope, leading to the difficult to study the plastic deformation behavior. With high spatial and temporal resolution instrumented nanoindentation, an experimental investigation into the serrated flow that is created during the plastic deformation at different loading rate was conducted. The results showed that low loading rate promote conspicuous pop-in events and high loading rate suppress pop-in behavior. The reason is that a single shear band is sufficient to render the plastic strain at low loading rate but multiple shear bands is required at high loading rate. To gain a better understanding of the mechanism despite the characteristic lack of periodicity in the intermittent pop-in events. Ergodically processing is introduced to demonstrate the statistic distributions of the strain burst size. The results showed that the smaller strain bursts are more probable and follow a power-law distribution and the exponent is constant about 1.45 at all experimental loading rates. For a given loading rate, with increasing the strain burst size, the distributions of the strain burst sizes do not follow a power-law distribution but decrease exponentially in probability. Finally, based on the strain rate sensitivity of hardness, we estimated the volume of the shear transformation zone.

Keywords: Metallic glass; Nanoindentation; Strain bursts; Ergodically processing; Strain rate sensitivity; shear transformation zone