热老化对铸造双相不锈钢组织和性能的影响

Effect of Thermal Aging on Microstructure and Properties of Casting Duplex Stainless Steel

为了查明导致铸造双相不锈钢热老化脆化的主要原因,研究了铸造双相不锈钢在400℃下老化15 000h过程中示波冲击性能与显微组织,分析了热老化时间对力学性能和显微组织结构的影响.结果表明,随着热老化时间的延长,冲击性能明显下降,断裂方式由最初的韧性断裂转变为脆性断裂,冲击断口形貌也显示出相同的规律.通过TEM观察发现,铁素体相在热老化3 000h后发生了调幅分解,分解的产物为富Cr的α′相和富Fe的α″相.随着老化时间的延长,调幅分解加剧,调幅分解的波长随之减小,在热老化15 000h后,调幅分解波长由11.89nm减小到5.37nm,调幅分解充分.

The paper aims to find out the main reason for the thermal aging and embrittlement of casting duplex stainless steel. The effect of thermal aging time on the impact properties and the microstructures of casting duplex stainless steel which was thermal aged at 400 ℃ for 15 000 h was investigated by using impact test and electron microscopy observation. The results showed that the impact performance decreased obviously, the fracture appearance and fracture mechanism were changed from ductile fracture to brittle fracture as the thermal aging time increased. Spinodal decomposition in ferrite occurred when the steel was thermal aged for 3000h at 400℃. The decomposition products were Cr-ricch a＇ and Fe-rich a＇. With the increase of aging time, spinodal decomposition intensified and the wavelengths of spinodal decomposition decreased. The wavelength of spinodal decomposition reduced from 11.89 nm to 5.37 nm if thermal aged for 15 000 h.