2205双相不锈钢的高温变形行为

HOT DEFORMATION BEHAVIOR OF 2205 DUPLEX STAINLESS STEEL

利用Gleeble-3800热力模拟试验机在温度为1223-1523 K,应变速率为0.01-10 s^(-1)的条件下进行了2205双相不锈钢热压缩变形实验,测定了真应力-真应变曲线,分析了变形组织。结果表明:奥氏体分布在随温度升高而含量增加的铁素体基体上,升高温度和降低应变速率可促进奥氏体发生动态再结晶。基于热变形方程计算得到了热变形激活能Q=451 kJ/mol,表观应力指数n=4.026。真应力-真应变曲线存在的"类屈服平台"效应与Z参数有关,随着Z参数的减小而逐渐增强。基于简化应力函数的ln Z与σ_p之间的线性关系在临界点(In Z_c=38.18)发生偏移;峰值应力与温度及应变速率的关系可表示为:σ_p=20.6lnε+1118002/T-266.8(ln Z>38.18);σ_p=9.1lnε+493874/T-701.9(1n Z≤38.18)。

During hot deformation of the duplex stainless steels consisting ofδ-ferrite andγ-austenite, their microstructure evolution and mechanical response are more complicated as compared with those of single-phase ferritic or austenitic stainless steels,especially for study of the mechanical behavior.In the present research,the hot deformation behavior of a 2205 duplex stainless steel has been investigated through uniaxial compression test using Gleeble-3800 thermal-mechanical simulator within the temperature range of 1223—1523 K and the strain rate range of 0.01—10 s^（-1）,the corresponding flow curves and their characters and microstructures have been determined and analyzed. Elongated austenite distributes in ferrite matrix,and the volume fraction of ferrite increases with rising temperature.Dynamic recrystallization of austenite is enhanced by increasing temperature and decreasing strain rate.Based on the constitutive equation for hot deformation,the apparent activation energy（Q） and the apparent stress exponent（n） of the steel are obtained to be about 451 kJ/mol and 4.026,respectively.There is a particular shape of flow curves,i.e.a yield point elongation-like effect, which is characterized by a non-strengthening plateau during the initial stages of plastic deformation. This yield point elongation-like effect increases with decreasing Zener-Hollomon parameter,Z.When used a simplified stress function,a deviation of linear relationship between ln Z and peak stress（σp） occurred at the critical value（ln Zc=38.18）.Relationships between peak stress and temperature and strain rate can be more simply described asσp = 20.6lnε＋ 1118002/T - 266.8（ln Z38.18）,andσp = 9.1lnε＋ 493874/T - 701.9（ln Z≤38.18）.