( 中南大學(xué) 材料科學(xué)與工程學(xué)院， 長沙 410083)
摘 要: 采用GLEEBLE-1500熱模擬機(jī)對Mg-Nd-Zn-Zr稀土鎂合金在溫度為250～450 ℃、 應(yīng)變速率為0.002～0.100 s-1、 最大變形程度為60％的條件下， 進(jìn)行高溫壓縮模擬實驗研究。 分析了實驗合金在高溫變形時的流變應(yīng)力和應(yīng)變速率及變形溫度之間的關(guān)系， 計算了變形激活能和應(yīng)力指數(shù)， 并研究了在熱壓縮過程中組織的變化， 為確定該稀土鎂合金的擠壓溫度提供了實驗依據(jù)。 結(jié)果表明： 合金的峰值流變應(yīng)力隨應(yīng)變速率的增大而增加， 隨溫度的升高而降低； 合金的變形激活能在300～400℃內(nèi)變化不大， 而在400～450 ℃時增加很大； 根據(jù)實驗分析認(rèn)為該稀土鎂合金擠壓溫度定在350～400 ℃左右為宜； 在350℃左右順利擠出的實驗合金有很好的力學(xué)性能： σb=275.5 MPa， δ=13.5%。
關(guān)鍵字: 稀土鎂合金； 熱模擬變形； 流變應(yīng)力； 變形激活能； 力學(xué)性能
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract: The stress-strain behavior of a Mg-2.5%Nd-0.5%Zn-0.4%Zr (mass fraction, %) alloy at various strain rates and different deformation temperatures were investigated under maxium strain of 60%. The microstructure of the experimental alloy was studied in the hot-compression procedure. The results show that the relation between stress and strain is affected obviously by the strain rate and deformation temperature. The peak flow stress becomes larger with the increasing strain rate at the same temperature, and gets smaller with the increasing deformation temperature at the same strain rate. The deformation activation energy increases greatly in the range of 400-450 ℃, and no more change in the range of 300-400 ℃. The alloy can be extruded successfully at 350 ℃ with σb of 275.5 MPa and δ of 13.5%. The mechanical properties of as-extrusion have a remarkable increasement compared with those of the as-cast at room temperature.
Key words: Mg-Nd-Zn-Zr magnesium alloy; hot-compression; peak flow stress; deformation activation energy; mechanical properties
