Mn18cr18N 护环钢热变形特征的研究

本文采用热压缩试验及微观模拟分析方法研究了Ｍｎ１８ｃｒ１８Ｎ钢热变形条件下的力学行为和动态组织变化。获得了该钢的热变形特征参数（σｐ、σｓ、εｐ、εｓ）和动态再结晶晶粒尺寸（ｄ）与Ｚｅｎｅｒ－Ｈｏｌｏｍｏｎ参数（Ｚ）之间的关系式。建立了该钢的高温屈服应力模型。可为数值模拟和护环热锻工艺的优化提供理论依据。

基于热加工图的钼金属热变形特征分析

钼金属产生变形需要具备一定的温度,即变形温度,一般在温度为900~1 450℃的情况下才会产生热变形性能,在以往的热压研究中得出钼金属的应变速为0.01~10 s^(-1)。为了深入研究钼金属热变形的特征,将采用动态材料模型对钼金属的热加工图进行组建,同时根据热加工图中呈现的热变形变化趋势对不同区域内的钼金属形态进行分析,以此达到对钼金属热变形特征的研究目的。文章对钼金属热变形特征研究的实验过程及结论进行梳理,以确保研究的有效性。

Characteristics of hot tensile deformation and microstructure evolution of twin-roll cast AZ31B magnesium alloys

High temperature tensile properties and microstructure evolutions of twin-roll-cast AZ31B magnesium alloy were investigated over a strain rate range from 10-3 to 1 s-1.It is suggested that the dominant deformation mechanism in the lower strain rate regimes is dislocation creep controlled by grain boundary diffusion at lower temperature and by lattice diffusion at higher temperatures,respectively.Furthermore,dislocation glide and twinning are dominant deformation mechanisms at higher strain-rate.The processing map,the effective diffusion coefficient and activation energy map of the alloy were established.The relations of microstructure evolutions to the transition temperature of dominant diffusion process,the activation energy platform and the occurrence of the full dynamic recrystallization with the maximum peak efficiency were analyzed.It is revealed that the optimum conditions for thermo-mechanical processing of the alloy are at a temperature range from 553 to 593 K,and a strain rate range from 7×10-3 to 2×10-3 s-1.

一种新型镍基高温合金的动态再结晶行为

采用等温热压缩实验研究了一种新型镍基高温合金在不同热变形条件下(变形温度1040~1120℃、应变量0.35~1.2、应变速率0.1 s^(-1))的动态再结晶行为。通过光学显微镜(OM)、扫描电子显微镜(SEM)和电子背散射衍射仪(EBSD)研究变形温度和应变量对合金热变形过程中组织演变和动态再结晶(DRX)形核机制的影响。结果表明,根据加工硬化率曲线能够准确确定DRX出现的临界应力和临界应变。合金的DRX晶粒体积分数随变形温度和应变量的增加而增加。在高温低应变速率下,不连续动态再结晶(DDRX)和连续动态再结晶(CDRX)形核机制同时发生。随着变形温度的升高,CDRX形核机制减弱,而CDRX机制在高温条件下占据主导。随着应变量的增加,合金中DDRX机制逐渐变强。热变形后期,CDRX仅作为辅助形核机制发挥作用。另外,Σ3孪晶界的形成有助于DRX晶粒的形核。