在室温至900 ℃温度范围内、不同初始应变速率(8×10-5、8×10-4和8×10-3 s-1)下,利用单向拉伸实验研究了温度与应变速率对Invar 36合金拉伸力学性能的影响,并选择室温、600和800 ℃进行三点弯曲实验,分析温度对Invar 36合金厚板回弹规律的影响。结果表明,Invar 36合金的屈服强度、抗拉强度随温度的升高而大幅降低;延伸率则先升高后降低,在600 ℃时出现峰值,达到69.2%,比室温提高了55%,这主要由于动态再结晶使塑性提高所致。当温度较低时(室温和500 ℃),应变速率对Invar 36合金力学性能影响不大;但当温度升高至800 ℃时,Invar 36合金的强度和塑性均随初始应变速率的减小而大幅减小,初始应变速率由8×10-3 s-1降至8×10-5 s-1,屈服强度、抗拉强度和延伸率分别降低了38%、47%和50%;由室温升高至800 ℃时,三点弯曲回弹量减小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, the mechanical properties of Invar 36 alloy were studied in the temperature range from room temperature to 900 ℃ under different initial strain rates (8×10-5, 8×10-4 and 8×10-3 s-1) by using 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 ℃ was investigated. The results indicate that 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 ℃.