文章信息/Info

Title:

Serrated flow dynamics in bulk metallic glasses

作者:

喬珺威; 李嬌嬌; 王重

材料科學(xué)與工程學(xué)院，太原理工大學(xué)

Author(s):

Qiao Junwei; Jiaojiao Li;  Zhong Wang

College of Materials Science and Engineering, Taiyuan University of Technology

關(guān)鍵詞:

非晶合金;  鋸齒流變;  剪切帶;  本征結(jié)構(gòu);  試樣尺寸;  加載條件

Keywords:

Amorphous alloys;  Serrated flows;  Shear bands;  Intrinsic structure;  Sample size;  Testing condition

DOI:

10.7502/j.issn.1674-3962.2017.03.07

文獻(xiàn)標(biāo)志碼:

A

摘要:

非晶合金在外力場(chǎng)的作用下會(huì)出現(xiàn)間接性的鋸齒流, 鋸齒具有空間和時(shí)間的無(wú)序分布性, 能夠反映塑性變形過(guò)程中剪切帶的演化過(guò)程。 借助于混沌理論、自組織臨界理論、統(tǒng)計(jì)分析、分形和平均場(chǎng)理論等數(shù)學(xué)方法進(jìn)行了鋸齒動(dòng)力學(xué)分析。發(fā)現(xiàn)非晶合金的塑性流變行為與材料的本征結(jié)構(gòu)、試樣尺寸、加載試驗(yàn)機(jī)的剛度、溫度和應(yīng)變速率等密切相關(guān)，揭示了非晶合金的塑性變形過(guò)程中剪切帶滑移不穩(wěn)定性的演化特點(diǎn)。 試樣尺寸小、低溫或高應(yīng)變速率下加載的的韌性非晶試樣的塑性流變動(dòng)力學(xué)呈現(xiàn)類自組織臨界狀態(tài),鋸齒的幅值分布具有無(wú)標(biāo)度性特點(diǎn)，剪切帶之間的交互作用強(qiáng)，剪切帶過(guò)程相對(duì)穩(wěn)定。低溫下大的分形維數(shù)說(shuō)明剪切帶分叉速率快，觸發(fā)了剪切帶之間的交互作用。簡(jiǎn)單的平均場(chǎng)理論證實(shí)了非晶的塑性可受應(yīng)變速率調(diào)控。這些結(jié)論為進(jìn)一步探索非晶合金的塑性提供了思路。

Abstract:

Intermittent serrated flows reflecting the evolution of shear bands, which is characterized by spatiotemporal disordered distribution, can be seen during compressive plastic deformation in amorphous alloys. Chaotic, self-organized criticality（SOC）, classical statistical analysis, fractal, and mean-filed theory model are used to investigate the dynamics of plastic flows in response to variant conditions. It is found that the serration dynamics significantly depends on intrinsic structural properties, sample size, stiffness of loading machine, temperature, and strain rate, which revealing the evolution of shear-band instability. SOC-like state can be obtained in ductile materials with small sample size under low temperatures or high strain rates. It hints about shear bands move in a scale-free intermittent fashion and the great interaction of shear bands. The largest shear-banding rate is indicated by the largest fractal dimension at low temperature, which shows an enhanced fractal behavior. Simple mean-filed theory model (MFT) verifies that plasticity can be tuned by imposed strain rates. These are of great implication for the exploration of plasticity in amorphous alloys.