To calculate the intrinsic contributions to the fracture toughness for the three microstructures, the values of uniform elongation, Young's modulus and Poisson's ratio for the three microstructures should be available. Based on the materials properties handbook, Young's modulus for Ti-17 alloy are taken as 112 GPa and Poisson's ratio is taken as 0.35 in the present paper. According to the regular patterns of the constitutive curves for titanium alloy, the uniform elongations for the three microstructures are all taken as half of their elongations, as shown in Table 4.
Table 5 shows the comparison between the fracture toughness values obtained from experiments and the prediction model for Ti-17 alloy. It can be found that this model has good prediction precisions for microstructures A, B and C, which are within 8%. In addition, It can be found that the intrinsic contributions for the three microstructures are generally located in the [76 View the MathML source, 81 View the MathML source] region, which do not show a big difference. However, their extrinsic contributions are dramatically different. For example, the extrinsic contribution of microstructure A is only 3.4 View the MathML source, but for microstructure C it can reach 16.5 View the MathML source. Generally speaking, the intrinsic fracture toughness constitutes the vast majority of the fracture toughness for Ti-17 alloy. However, the extrinsic fracture toughness, which is more sensitive to the lamellar features of Ti-17 alloy, can still exert big influence on the fracture toughness. Microstructure C which contains long and thick α platelets gets the most rugged crack propagation path and moderate plasticity among the three microstructures. Thus the good combination of above two factors results in the highest fracture toughness. Moreover, due to the nature of the near-β Ti-17 alloy, the α platelets in microstructure C get very high aspect ratios, which results in its high strength. Thus for Ti-17 alloy studied in present work, the long and thick α platelets in microstructure can realize a good combination of fracture toughness and strength. In other words, this means that the slow air cooling method after β forging of Ti-17 alloy should be given priority.
การคำนวณเงินสมทบ intrinsic ไปนึ่งกระดูกสำหรับ microstructures สาม ค่า elongation ที่สม่ำเสมอ โมดูลัสของยัง และอัตราส่วนของปัวซอง microstructures สามควรพร้อมใช้งาน ตามคู่มือคุณสมบัติวัสดุ โมดูลัสของยังสำหรับโลหะผสมตี้-17 ถูกนำเป็น 112 จะได้รับอัตราส่วนของปัวซองและ GPa เป็น 0.35 ในเอกสารปัจจุบัน มีทั้งหมดตามรูปแบบปกติของเส้นโค้งขึ้นในโลหะผสมไทเทเนียม elongations เครื่องแบบสำหรับ microstructures สามถ่ายเป็นครึ่งหนึ่งของ elongations ของพวกเขา ดังแสดงในตาราง 4Table 5 shows the comparison between the fracture toughness values obtained from experiments and the prediction model for Ti-17 alloy. It can be found that this model has good prediction precisions for microstructures A, B and C, which are within 8%. In addition, It can be found that the intrinsic contributions for the three microstructures are generally located in the [76 View the MathML source, 81 View the MathML source] region, which do not show a big difference. However, their extrinsic contributions are dramatically different. For example, the extrinsic contribution of microstructure A is only 3.4 View the MathML source, but for microstructure C it can reach 16.5 View the MathML source. Generally speaking, the intrinsic fracture toughness constitutes the vast majority of the fracture toughness for Ti-17 alloy. However, the extrinsic fracture toughness, which is more sensitive to the lamellar features of Ti-17 alloy, can still exert big influence on the fracture toughness. Microstructure C which contains long and thick α platelets gets the most rugged crack propagation path and moderate plasticity among the three microstructures. Thus the good combination of above two factors results in the highest fracture toughness. Moreover, due to the nature of the near-β Ti-17 alloy, the α platelets in microstructure C get very high aspect ratios, which results in its high strength. Thus for Ti-17 alloy studied in present work, the long and thick α platelets in microstructure can realize a good combination of fracture toughness and strength. In other words, this means that the slow air cooling method after β forging of Ti-17 alloy should be given priority.
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