对800H合金进行单道次压缩热模拟实验, 研究了该合金在850­­—1100℃和0.01—30 s^-1条件下的热变形行为,建立了基于动态材料模型的热加工图, 结合微观组织的演变规律, 分析了工艺参数对800H合金热加工性能的影响.结果表明: 当应变速率超过1 s^-1时, 800H合金在热变形过程中产生了明显的绝热温升现象,该现象随着变形温度的降低或应变速率的升高而更加明显; 通过转动动态再结晶机制,在大应变速率下, 剪切带附近产生了超细再结晶晶粒; 当变形温度低于950℃时, 在低应变速率条件下,应变诱导析出效应对晶界移动产生了具有钉扎效应的“齐纳压力'', 增大了热变形激活能, 抑制了动态再结晶的发生;利用加工图可以确定不同变形条件区域内的微观组织特征以及800H合金的最佳热加工工艺参数范围为:975—1100℃和0.01—0.3 s^-1.

During the processing of hot working, the material undergoes shape and microstructural changes depending on the processing history. Therefore, the optimization of the processing parameters such as temperature, strain and strain rate is of great importance to achieve a defect-free component with desired microstructure. In order to optimize the hot working technology, the hot deformation behavior and hot workability of alloy 800H in the temperature range of 850-1100℃ and strain rate range of 0.01-30 s^-1 were investigated with single-pass compression tests on MMS-300 thermo-simulation machine. The flow stress-strain curves of alloy 800H under different deformation conditions were plotted. The influence of precipitation on hot deformation below 950℃ at low strain rates was studied. The processing map was established based on dynamic materials model. The effect of processing parameters on hot workability and the mechanism of hot deformation in different regimes of processing map were analyzed combined with the observation of microstructural evolution. The results revealed that the adiabatic heating is generated obviously if strain rate is higher than 1 s^-1 during hot deformation, which leads to flow softening via the mechanism of rotational dynamic recrystallization (DRX). Some ultrafine grains can be found in the core of shear bands. The magnitude of temperature rising and subsequent softening are supposed to be more significant at higher strain rates or lower deformation temperatures. The occurrence of DRX is inhibited by “Zener effect'' which pins the migration of grain boundaries and increases the activation energy of hot deformation. The alloy 800H exhibits a better workability in deformation temperature range from 975℃  to 1100℃ and strain rate range from 0.01 s^-1 to 0.3 s^-1 with the efficiency of power dissipation within the range of 35%—48%.