摘要：The hot tensile deformation behavior of ZA73 magnesium alloy were investigated in the temperature range of 150-300℃ and strain rates of 0. 001s-1 and 0. ls-1 , respectively, by thermo-mechanical simulation. The hot-forming processing parameters were then determined, combined with microstructural observation and real extrusion experiment. The results showed that the deformation temperature and strain rate are the key factors influencing the flow stress and plasticity. The flow stress decreases with the increase of temperature and the decrease of strain rate. At lower strain rate, the plasticity becomes worse when the deformation temperature is higher than 200℃. Comparatively, at higher strain rate, the plasticity improves with the temperature raising except at 250℃. Moreover, when deformed in the temperature range of 200-250℃, net-worked dendritic microstructural feature disappears, instead, the second phases disperse in the matrix in the form of particles of smaller size. The microstructure goes coarse when deformed at 300℃ under lower strain rate. It is concluded that the increase of the amount of small particles and the coarsening of microstructure lead to the deterioration of hot plasticity. Higher strain rate and temperature is considered to favour hot deformation. Bars were extruded at 350℃ under higher strain rate of about 0. 1s-1. The tensile ultimate strength of the as-extruded bar reaches 355MPa, in the mean time maintaining a high elongation of 19％. In addition to, the grain size was refined to 3-6μm.%在應變速率為0.001s(-1)和0.1s(-1),溫度為150-300℃的條件下,采用熱模擬對ZA73鎂合金的高溫拉伸變形行為進行了研究,并結合顯微組織觀察和擠壓試驗,分析確定了適合該合金的熱加工工藝.結果表明:變形溫度和應變速率是影響ZA73合金流變應力和塑性的關鍵參數,應變速率一定時,流變應力隨溫度的增加而降低;溫度一定時,流變應力隨應變速率的提高而增加.低應變速率下,溫度高于200℃塑性反而降低;高應變速率下,合金的塑性隨著溫度的增加而提高,但在250℃時塑性出現反常變化.在200-250℃范圍內變形時,鑄態枝晶網狀組織特征消失,第二相化合物呈顆粒狀彌散分布于基體中,尺寸明顯細化;300℃變形時,低應變速率下合金組織明顯粗大.細小第二相粒子增多和組織粗化導致合金熱塑性降低.較高的應變速率和較高的溫度有利于合金的熱變形.在350℃和較高應變速率(約0.1s(-1))下,擠壓棒材的抗拉強度達355MPa,延伸率仍保持19%,晶粒尺寸細化至3-6μm.
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