新型亞穩(wěn)β鈦合金Ti2448的溫變形行為及本構(gòu)模型Warm deformation behavior of new kind of metastable β titanium alloy Ti2448 and its constitute model

采用壓縮實驗研究應(yīng)變速率和變形溫度對新型亞穩(wěn)β鈦合金Ti2448溫變形行為的影響。熱模擬壓縮實驗在Gleeble?3800 熱模擬機上進行，變形溫度為473~673 K，應(yīng)變速率為0.001~10 s ?1 ，變形程度為45%。結(jié)果表明：在高、低應(yīng)變速率下合金呈現(xiàn)不同的變形特性。低應(yīng)變速率(0.001~0.1 s ?1 )下，流動曲線呈現(xiàn)明顯的應(yīng)變硬化特性；在10 s ?1 的高應(yīng)變速率下，流動應(yīng)力在達(dá)到飽和后，因溫升效應(yīng)而下降；在673 K 變形溫度下流動應(yīng)力因材料內(nèi)部相變而具有顯著的應(yīng)變速率負(fù)敏感性。基于分段外推飽和模型和改進的Voce 模型分別構(gòu)建Ti2448 合金在溫變形高、低應(yīng)變速率下的流動應(yīng)力模型；該模型得到的預(yù)測曲線(應(yīng)力—應(yīng)變曲線)和實驗曲線吻合較好，能夠有效預(yù)測 Ti2448 合金在溫變形過程中的流動應(yīng)力，其中，改進的 Voce 模型能同時較好地描述飽和型和非飽和型應(yīng)變硬化特性。

The effects of strain rate and deformation temperature on warm deformation behavior of a new kind of metastable β titanium alloy Ti2448 were investigated by using compression tests. The experiments were carried out on a Gleeble?3800 thermomechanical simulator at deformation temperatures of 473?673 K, strain rates of 0.001?10 s ?1 , and height direction reduction of 45%. The results show that there are different deformation behaviors at high and low strain rates. At low strain rates (0.001?0.1 s ?1 ), there are obvious work hardening behaviors in flow stress curves. At the high strain rate of 10 s ?1 , the alloy presents obvious hardening firstly, then saturated state and further softening caused by temperature rise finally. At 673 K, the alloy significantly exhibits the stain rate negative sensitivity because of the phase change. Based on the model in which the whole stress—strain curve is divided into the strain hardening part and the saturated state part and the modified Voce model, constitutive models were developed to describe the flow behaviors of Ti2448 alloy at high and low strain rates, respectively. The stress—strain curves predicted by the developed model well fit with the experimental results, which confirms that the developed model can predict the flow stress of Ti2448 alloy validly and the modified Voce model can describe the strain hardening behavior of both the saturated state and the unsaturated state.

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