溫度與應變速率對Invar 36合金變形行為的影響

溫度與應變速率對Invar 36合金變形行為的影響Effect of Temperature and Strain Rate on Deformation Behavior of Invar 36 Alloy

在室溫至900℃溫度范圍內(nèi)、不同初始應變速率（8×10-5，8×10-4和8×10-3 s-1）下利用單向拉伸試驗研究了溫度與應變速率對Invar 36合金拉伸力學性能的影響，并選擇室溫、600和800 ℃進行三點彎曲實驗分析溫度對Invar 36合金厚板回彈規(guī)律的影響。結果表明，Invar 36合金的屈服強度、抗拉強度隨溫度的升高而大幅降低；延伸率則先升高后降低，在600 ℃時出現(xiàn)峰值，達到69.2%，比室溫提高了55%，主要由于動態(tài)再結晶使塑性提高所致。當溫度較低時（室溫和500 ℃），應變速率對Invar 36合金力學性能影響不大；但當溫度升高至800 ℃時，Invar 36合金的強度和塑性均隨初始應變速率的減小而大幅減小，初始應變速率由8×10-3 s-1降至8×10-5 s-1，屈服強度、抗拉強度和延伸率分別降低了38%、47%和50%；由室溫升高至800 ℃時，三點彎曲回彈量減小87.0%。

Since the thermal expansion coefficient of Invar 36 alloy is so low that it matches the composite materials well. It is very suitable as the material of composite material forming mould. Invar 36 alloy mould surface is usually produced by hot pressing technology. The hot pressing temperature and strain rate severely affect the quality of mould surface. In this work, mechanical properties of Invar 36 alloy were studied in temperature range from room temperature to 900 ℃ under different initial strain rates (8×10-5, 8×10-4 and 8×10-3 s-1) through uniaxial tensile tests. The effect of temperature on the springback trend of thick Invar 36 alloy sheet by three-point bending tests at room temperature, 600 ℃ and 800 ℃. The results indicate the yield strength and ultimate tensile strength of Invar 36 alloy significantly decrease with increasing temperature. Meanwhile, the elongation firstly increases and then decreases with the increase of temperature. It reaches a peak value of 69.2% at 600 ℃ and increases by 55% than that at ambient temperature, which mainly results from the plasticity improvement by dynamic recrystallization. Invar 36 alloy at lower temperature (room temperature and 500 ℃) shows insensitive to the strain rate. Nevertheless, the strength and plasticity at 800 ℃substantially decrease with decreasing strain rate. When the strain rate decreases from 8×10-3 s-1 to 8×10-5 s-1, the yield strength, ultimate tensile strength and elongation reduce by 38%, 47% and 50%, respectively. The three-point bending springback value decreases by 87.0% when the tested temperature increases from room temperature to 800 ℃.

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