Austempering ductile iron (ADI) is an attractive material due to its excellent comprehensive mechanical properties. However, the deficit in elongation and toughness always threatens its security application. Two-step ...Austempering ductile iron (ADI) is an attractive material due to its excellent comprehensive mechanical properties. However, the deficit in elongation and toughness always threatens its security application. Two-step austempering process is an effective way to improve elongation and toughness simultaneously. In the present work, the influence of the amount, morphology and distribution of ferrite and austenite on mechanical properties of ADI under different second-step austempering parameters has been analyzed. Results show that the amount of austenite and its carbon content decrease with increasing of second-step temperature. Carbide begins to precipitate as second-step austempering temperature reaches 380 °C. These factors together influence the mechanical properties of two-step Cu-alloyed ADI. Impact energy and fracture toughness are strongly affected by second-step austempering temperature, and are dramatically decreased with increase of second-step austempering temperature. Elongation remains constant when the second-step temperature is below 360 °C, and then it is rapidly decreased with further increase of second-step temperature. Strength is slightly influenced by second-step temperature. Ferrite morphology is not influenced by second-step austempering duration, while blocky retained austenite size is slightly decreased with the increasing of second-step austempering time. The amount of retained austenite is decreased while the carbon content of retained austenite is increased with the extending of second-step austempering time. The substructure of austenite is transformed from dislocation to twin when second-step austempering time exceeds 60 min. Strength and elongation are improved slightly with extending of second-step time. Impact energy and fracture toughness initially decrease with the extending of second-step time, and then remain constant when the time is longer than 60 min. This is a result of austenite content decreasing and carbon content of austenite increasing. The second-step austempering time mainly influences austenite content and its carbon content, which is a result of carbon diffusion behavior variation.展开更多
针对文献[Xu R et al.,IEEE Trans.Biomed.Eng.,2014]的多尺度图像分解模型,该文提出了Alternating Direction Implicit (ADI)格式下的多尺度图像分解算法,并证明了在该模型下ADI格式的收敛性和稳定性,进一步,通过对不同图像的数值实验...针对文献[Xu R et al.,IEEE Trans.Biomed.Eng.,2014]的多尺度图像分解模型,该文提出了Alternating Direction Implicit (ADI)格式下的多尺度图像分解算法,并证明了在该模型下ADI格式的收敛性和稳定性,进一步,通过对不同图像的数值实验,验证了该文提出的算法具有更好的纹理提取效果.展开更多
基金financially supported by the National Natural Science Foundation of China.(Grant Nos.51374086 and 51674094)
文摘Austempering ductile iron (ADI) is an attractive material due to its excellent comprehensive mechanical properties. However, the deficit in elongation and toughness always threatens its security application. Two-step austempering process is an effective way to improve elongation and toughness simultaneously. In the present work, the influence of the amount, morphology and distribution of ferrite and austenite on mechanical properties of ADI under different second-step austempering parameters has been analyzed. Results show that the amount of austenite and its carbon content decrease with increasing of second-step temperature. Carbide begins to precipitate as second-step austempering temperature reaches 380 °C. These factors together influence the mechanical properties of two-step Cu-alloyed ADI. Impact energy and fracture toughness are strongly affected by second-step austempering temperature, and are dramatically decreased with increase of second-step austempering temperature. Elongation remains constant when the second-step temperature is below 360 °C, and then it is rapidly decreased with further increase of second-step temperature. Strength is slightly influenced by second-step temperature. Ferrite morphology is not influenced by second-step austempering duration, while blocky retained austenite size is slightly decreased with the increasing of second-step austempering time. The amount of retained austenite is decreased while the carbon content of retained austenite is increased with the extending of second-step austempering time. The substructure of austenite is transformed from dislocation to twin when second-step austempering time exceeds 60 min. Strength and elongation are improved slightly with extending of second-step time. Impact energy and fracture toughness initially decrease with the extending of second-step time, and then remain constant when the time is longer than 60 min. This is a result of austenite content decreasing and carbon content of austenite increasing. The second-step austempering time mainly influences austenite content and its carbon content, which is a result of carbon diffusion behavior variation.
文摘针对文献[Xu R et al.,IEEE Trans.Biomed.Eng.,2014]的多尺度图像分解模型,该文提出了Alternating Direction Implicit (ADI)格式下的多尺度图像分解算法,并证明了在该模型下ADI格式的收敛性和稳定性,进一步,通过对不同图像的数值实验,验证了该文提出的算法具有更好的纹理提取效果.
