(1. 重慶理工大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400050；
2. 重慶大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400044)
摘 要: 為了優(yōu)化鎂合金棒材的微觀組織，借鑒正擠壓與多道次等通道擠壓的特點提出了擠壓(Extrusion)-剪切(Shear)復(fù)合擠壓工藝(簡稱ES)，制造了多副適合工業(yè)臥式擠壓機上的ES變形組合凹模，進行了ES擠壓和普通擠壓實驗。構(gòu)建了ES擠壓和普通擠壓的三維熱力耦合的有限元模型及計算條件，模擬了ES擠壓過程的擠壓力、有效應(yīng)力及應(yīng)變演變規(guī)律，利用光學(xué)顯微鏡、透射及掃描電鏡對微觀組織演變進行了觀察與分析。結(jié)果表明：根據(jù)對成形力演變過程和數(shù)值的分析，ES擠壓過程可以分為四個階段，其中有三個階段擠壓力變化較小，ES成形所需的擠壓力大約是普通擠壓所需擠壓力的1.67倍；與普通擠壓相比，ES擠壓可大大提高鎂合金的有效應(yīng)變，最大有效應(yīng)變可提高到3.8倍；ES成形可以改善鎂合金中β相的形態(tài)與分布，不僅細化棒材表層晶粒，而且心部晶粒也得到了細化；動態(tài)再結(jié)晶晶粒及變形位錯會越多，再結(jié)晶晶粒越細；帶有轉(zhuǎn)角的ES模具產(chǎn)生的剪切作用是鎂合金發(fā)生多次動態(tài)再結(jié)晶的主要原因，在ES擠壓過程中，第二相β相對基體有剪切和釘扎作用。
關(guān)鍵字: 變形鎂合金；ES變形；微觀組織；動態(tài)再結(jié)晶；應(yīng)力狀態(tài)
（1. College of Materials Science and Engineering, Chongqing University of Technology, Chongqing 400050, China;
2. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China）
Abstract:Based on the characteristics of direct extrusion and multi channels extrusion, the extrusion and shear (ES) was proposed to optimize the microstructures of magnesium alloy rods, and the ES deformation composite die suitable for industrial horizontal extrusion machine was manufactured. The ES extrusion and ordinary extrusion experiments have been carried out. The three dimensional finite element thermodynamic coupling model and conditions of ES extrusion and ordinary extrusion were established to simulate the evolution of extrusion pressure and cumulative stresses and strains during ES process. The microstructures evolution were studied by metallography, transmission and scanning electron microscopy. The results show that, according to the analysis about the values of forming forces, ES process can be divided into four stages, and three of which have little change of extrusion force. The extrusion forces of ES process is about 1.67 times that of ordinary direct extrusion. Compared with ordinary direct extrusion, ES process can greatly increase the cumulative strains of magnesium alloy, and the maximum strain is increased to 3.8 times. ES process can refine the alloy, improve the morphology and distribution of β phase and refine the grain sizes. ES process can refine not only the surface grains but also the center grains in the rods. The more the dynamic recrystallized grains and deformation dislocations, the finer the recrystallized grains. The main reason for multiple dynamic recrystallization of magnesium alloy is shear caused by ES die with shearing angles. During the process of ES deformation, the second β-phase has shearing and nailing action against the matrix alloy.
Key words: wrought magnesium alloy; ES deformation; microstructure; dynamic recrystallization; stress state
