SP700钛合金低温超塑成形数值模拟与机理研究

Study on numerical simulation and mechanism of low-temperature superplastic forming of SP700 titanium alloy

针对SP700钛合金低温超塑特性的工程化应用需求,通过数值模拟与超塑成形工艺参数优化保证了成形件的几何精度。首先依据前期高温拉伸试验确定了SP700钛合金合适的超塑成形参数,基于Backofen模型描述了SP700钛合金稳态阶段的流动应力,利用确定的气压加载路径完成了SP700钛合金盒型件超塑气胀成形工艺试验。采用PVX测厚仪测量了盒型件不同区域的厚度分布,与数值仿真结果对比,验证了SP700钛合金超塑成形数值仿真的预测精度。通过室温拉伸分析了SP700钛合金低温超塑成形后的力学性能。结果表明,SP700钛合金具有优异的低温超塑性,可成形质量合格的盒型件,其数值仿真结果与试验结果吻合良好,预测精度可达90%以上。经过超塑成形后,SP700钛合金组织性能并无明显变化,仍具有较优异的力学性能。

According to the demand of engineering application of low-temperature superplastic characteristics of SP700 titanium alloy,the numerical simulation and superplastic forming process parameter optimization were used to guarantee the geometric accuracy of the formed parts.Firstly,the suitable superplastic forming parameters were determined according previous high-temperature tensile tests.The flow stress of SP700 titanium alloy during steady state was depicted based on Backofen model.The determined pressure loading path was used to complete the superplastic gas-bulging forming tests of SP700 titanium alloy box-shaped parts.The thickness distributions of the box-shaped part in different areas were measured by PVX thickness gauge,and compared with the numerical simulation results,the prediction accuracy of numerical simulation of superplastic forming of SP700 titanium alloy was verified.The mechanical properties after low temperature superplastic forming of SP700 titanium alloy were analyzed by room-temperature tension.The results show that SP700 titanium alloy has excellent superplasticity at low temperature and can be used to form box-shaped parts with qualified quality.The numerical simulation results agree well with the test results,and the prediction accuracy can reache more than 90%.The microstructure and properties of SP700 titanium alloy have no obvious change,which still has excellent mechanical properties after superplastic forming.