新聞資訊
擠壓態(tài)ZK60鎂合金室溫拉-壓不對(duì)稱性研究
發(fā)布人：上海艾荔艾金屬材料有限公司www.85978597.cn
更新時(shí)間：2015-12-23
基于室溫軸向拉伸和壓縮實(shí)驗(yàn)研究了擠壓態(tài) ZK60 鎂合金的拉-壓不對(duì)稱性。通過(guò)修正黏塑性自洽模型，建立了耦合滑移和孿生的晶體塑性力學(xué)模型，模擬了擠壓態(tài) ZK60 鎂合金軸向拉、壓力學(xué)行為，分析了基面、柱面、錐面滑移及{1012}1011拉伸孿生和{1011}1012壓縮孿生在塑性變形過(guò)程中的激活及演變情況。結(jié)合實(shí)驗(yàn)與模擬，從微觀塑性變形機(jī)制角度分析了具有初始擠壓態(tài)絲織構(gòu)的鎂合金產(chǎn)生拉-壓不對(duì)稱性的機(jī)理。
擠壓態(tài)ZK60鎂合金室溫拉-壓不對(duì)稱性研究RESEARCH ON THE TENSION-COMPRESSION ASYMMETRY OF?AS-EXTRUDED ZK60 MAGNESIUM ALLOYS AT ROOM TEMPERATURE
基于室溫軸向拉伸和壓縮實(shí)驗(yàn)研究了擠壓態(tài) ZK60 鎂合金的拉-壓不對(duì)稱性。通過(guò)修正黏塑性自洽模型，建立了耦合滑移和孿生的晶體塑性力學(xué)模型，模擬了擠壓態(tài) ZK60 鎂合金軸向拉、壓力學(xué)行為，分析了基面、柱面、錐面滑移及{1012}1011 ? ?拉伸孿生和{1011}1012 ? ?壓縮孿生在塑性變形過(guò)程中的激活及演變情況。結(jié)合實(shí)驗(yàn)與模擬，從微觀塑性變形機(jī)制角度分析了具有初始擠壓態(tài)絲織構(gòu)的鎂合金產(chǎn)生拉-壓不對(duì)稱性的機(jī)理。結(jié)果表明：軸向拉伸過(guò)程中拉伸孿生和壓縮孿生都較難激活，變形初期以基面滑移為主，由于基面滑移取向因子較低，導(dǎo)致屈服應(yīng)力較高；隨著晶粒轉(zhuǎn)動(dòng)，基面滑移分切應(yīng)力降低，應(yīng)力逐步升高，變形機(jī)制轉(zhuǎn)為以柱面滑移為主，輔以錐面<c+a>滑移，應(yīng)變硬化率較低，應(yīng)力-應(yīng)變曲線較平穩(wěn)。軸向壓縮前期，臨界剪切應(yīng)力較低的拉伸孿生大量激活，導(dǎo)致屈服應(yīng)力較低；應(yīng)變達(dá)到 6.0%后拉伸孿生逐漸飽和，相對(duì)活動(dòng)量快速降低，硬化率迅速提高，由于大量孿晶界對(duì)位錯(cuò)滑移形成阻礙，滑移機(jī)制未出現(xiàn)大量激活；軸向壓縮后期，隨著應(yīng)力的持續(xù)升高，壓縮孿生啟動(dòng)，相對(duì)活動(dòng)量迅速上升，塑性變形積累的應(yīng)力得以釋放，硬化率降低。因此，擠壓絲織構(gòu)狀態(tài)決定了鎂合金在室溫軸向拉、壓變形過(guò)程中的變形機(jī)制存在明顯區(qū)別，從而導(dǎo)致擠壓鎂合金產(chǎn)生顯著軸向拉-壓不對(duì)稱。?
Most wrought magnesium alloys exhibit a significant tension-compression asymmetry in yield?and work hardening behavior. To some extent, the widespread implementation of wrought magnesium alloys is?
hindered due to this disadvantage in some special conditions. In order to quantitatively analyze the effects of the?deformation mechanisms on the tension-compression asymmetry of wrought Mg alloy, in this paper, the plastic?deformation behavior of the as-extruded ZK60 magnesium alloy under uniaxial tension and compression at room?temperature was investigated by the crystal plasticity simulation and experimental methods. The crystal plasticity?constitutive model which includes slip and twinning mechanism was established by modifying the viscoplastic?self-consistent (VPSC) model. With this model, the activation and evolution of basal slip, prismatic slip,?pyramidal slip, {1012}1011 ? ? tensile twinning and {1011}1012 ? ? compression twinning are quantitatively studied?during the process of uniaxial tension and compression deformation. Tensile-compression asymmetry of the?as-extruded ZK60 alloy which has initial extruded fiber texture is analyzed from the microscopic plastic?deformation mechanism. The results show that the tension and compression twinning in the axial?tension-compression process are difficult to active, basal slip is the main deformation mode in the early stage of?deformation, but the orientation factor of basal slip is low and has a hard orientation resulting higher yield stress.?With the rotation of grains, the critical shear stress of basal slip reduced, stress continues increasing and prismatic?slip became the main deformation mechanism, pyramidal<c+a> slip also has a very high activity. At this stage, the?strain hardening rate is low and the stress-strain curve is smooth. In the early stage of compression, the tensile?twinning has a high activity due to its low critical shear stress (CRSS), which leading to a lower yield stress. The?tensile twinning gradually saturated after the strain reaching 6.0%. And then, the relative activity decreased?rapidly and the hardening rate increased at the same time. Since the large numbers of twin boundaries hinder the?movement of dislocation slip, slip is not the major mechanism. In the later stage, the compression twinning start?activation and its relative activity rise rapidly, the accumulated stress during plastic deformation can be released?and then the hardening rate decreased. It can see that, the variation in the relative activity of each deformation?mode during compression deformation is much more complex than tension. The yield asymmetry and different?work hardening behavior could be attributed to the combined effects of the strong fiber texture and the polar?nature of twinning.
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