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Alloying is one of the key approaches to improve the mechanical properties and thermal resistance of SiMo ductile iron. This paper reviews the effects of alloying elements on the microstructure and properties of SiMo ductile iron. A systematic study on multi-element alloyed SiMo ductile iron was carried out targeting exhaust manifolds of high peak-pressure diesel engines and gas engines. The results show that when the mass fraction of Mo increases from 0.9% to 1.46%, the volume fraction of carbides in the microstructure rises, leading to increases in the tensile strength, yield strength and hardness of SiMo ductile iron, while the elongation decreases by 50%. Vanadium alloying elevates the tensile strength but reduces the elongation of SiMo ductile iron; the material achieves satisfactory room-temperature mechanical properties at a V mass fraction of 0.4%. The short-term tensile strength at 800 ℃ increases with the rise of V content, yet no significant change is observed when the V mass fraction exceeds 0.4%. Among the multi-element alloyed SiMo ductile irons, the V-Nb alloyed SiMo ductile iron reaches a high-temperature tensile strength of 59 MPa, while the V-Cr and V-Nb-Cr alloyed variants exhibit high-temperature strengths of 61~64 MPa. These values meet the high-temperature tensile strength requirements for SiMo ductile iron applied in exhaust manifolds of high peak-pressure diesel engines and gas engines.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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