Microstructure evolution and properties of hot-extruded Inconel 625 alloy were investigated at different creep temperatures, aging time and strain rates. The experimental results indicate that the Inconel 625 alloy ex...Microstructure evolution and properties of hot-extruded Inconel 625 alloy were investigated at different creep temperatures, aging time and strain rates. The experimental results indicate that the Inconel 625 alloy exhibits an excellent creep resistance at 700 ℃ and below. When the creep temperature rises to 750 ℃, the creep resistance falls drastically due to the failure of phase transformation strengthening and the precipitation of a large amount of δ phase and σ phase at the grain boundary. The special temperature-sensitive characteristics of Inconel 625 alloy play a very important role in its fracture. When the strain rate is 8.33×10^-3s^-1, the strength of the specimen is higher than that of other parameters attributed to the effect of phase transformation strengthening. With the increase of Ni3(Al, Ti), the phase transformation strengthening inhibits thickening of the stacking faults into twins and improves the overall mechanical properties of the alloy. With the increase of the aging time, the granular Cr-rich M23C6 carbides continue to precipitate at the grain boundary, which hinders the movement of the dislocations and obviously increases the strength of the samples. Especially, the yield strength increases several times.展开更多
In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigat...In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigated. The creep tests were conducted at 750°C, 90 and 100 MPa. In the pre-strained samples, the grain boundary shielding ratio by precipitates was larger than that of the non-pre-strained sample. In addition, in the pre-strained samples the size of the M23C6 carbide in the grains was finer than in the non-pre-strained sample. The W content in the M23C6 carbide in the pre-strained samples tended to be larger than in the non-pre-strained sample. Therefore, the Ostwald ripening of the carbide was delayed and the size of M23C6 carbide was thought to be fine for a long time. These observations show that creep strength in the pre-strained samples is higher than that of the non-pre-strained sample because of both precipitation strengthening inside of the grains and grain boundaries.展开更多
以COST-FB2转子钢为研究对象,利用冲击试验、高温拉伸试验、硬度测试、扫描电镜、透射电镜及X射线衍射仪等测试方法研究了630℃长期时效中COST-FB2转子钢组织和性能的变化。结果表明:随着时效时间延长,冲击功、硬度和高温强度都呈下降趋...以COST-FB2转子钢为研究对象,利用冲击试验、高温拉伸试验、硬度测试、扫描电镜、透射电镜及X射线衍射仪等测试方法研究了630℃长期时效中COST-FB2转子钢组织和性能的变化。结果表明:随着时效时间延长,冲击功、硬度和高温强度都呈下降趋势,冲击韧性在2000h后下降较为明显,后逐渐趋于稳定。硬度(HBW)总体处在较高水平(2479.4MPa),高温塑性未见明显变化。M_(23)C_(6)碳化物尺寸及含量有所增长,但未见明显粗化;Laves相尺寸增长更明显并在晶界处聚集,但未形成链状。Laves相的析出长大与聚集是导致冲击韧性下降的主要原因。研究结果认为630℃时效至5000 h COST-FB2钢能够保持较高的高温稳定性。展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51664041,51561021,and 51665032)in part by Longyuan Youth Innovation and Entrepreneurship ProjectsBRICS STI Framework Programme
文摘Microstructure evolution and properties of hot-extruded Inconel 625 alloy were investigated at different creep temperatures, aging time and strain rates. The experimental results indicate that the Inconel 625 alloy exhibits an excellent creep resistance at 700 ℃ and below. When the creep temperature rises to 750 ℃, the creep resistance falls drastically due to the failure of phase transformation strengthening and the precipitation of a large amount of δ phase and σ phase at the grain boundary. The special temperature-sensitive characteristics of Inconel 625 alloy play a very important role in its fracture. When the strain rate is 8.33×10^-3s^-1, the strength of the specimen is higher than that of other parameters attributed to the effect of phase transformation strengthening. With the increase of Ni3(Al, Ti), the phase transformation strengthening inhibits thickening of the stacking faults into twins and improves the overall mechanical properties of the alloy. With the increase of the aging time, the granular Cr-rich M23C6 carbides continue to precipitate at the grain boundary, which hinders the movement of the dislocations and obviously increases the strength of the samples. Especially, the yield strength increases several times.
文摘In order to clarify the reason why the creep rupture time of pre-strained Ni-23Cr-7W Alloy (HR6W) is longer than that of the non-pre-strained HR6W, microstructures of HR6W after a series of creep tests were investigated. The creep tests were conducted at 750°C, 90 and 100 MPa. In the pre-strained samples, the grain boundary shielding ratio by precipitates was larger than that of the non-pre-strained sample. In addition, in the pre-strained samples the size of the M23C6 carbide in the grains was finer than in the non-pre-strained sample. The W content in the M23C6 carbide in the pre-strained samples tended to be larger than in the non-pre-strained sample. Therefore, the Ostwald ripening of the carbide was delayed and the size of M23C6 carbide was thought to be fine for a long time. These observations show that creep strength in the pre-strained samples is higher than that of the non-pre-strained sample because of both precipitation strengthening inside of the grains and grain boundaries.
文摘以COST-FB2转子钢为研究对象,利用冲击试验、高温拉伸试验、硬度测试、扫描电镜、透射电镜及X射线衍射仪等测试方法研究了630℃长期时效中COST-FB2转子钢组织和性能的变化。结果表明:随着时效时间延长,冲击功、硬度和高温强度都呈下降趋势,冲击韧性在2000h后下降较为明显,后逐渐趋于稳定。硬度(HBW)总体处在较高水平(2479.4MPa),高温塑性未见明显变化。M_(23)C_(6)碳化物尺寸及含量有所增长,但未见明显粗化;Laves相尺寸增长更明显并在晶界处聚集,但未形成链状。Laves相的析出长大与聚集是导致冲击韧性下降的主要原因。研究结果认为630℃时效至5000 h COST-FB2钢能够保持较高的高温稳定性。
