| Along with development of aviation and spacelight, titanium alloys are expected as good matching of strength, plastic and toughness. TC21 alloy was excogitated by Northwest institute for Non-ferrous Metal Research, in 2001.It is the first titanium alloy of damage tolerance which have the independent intellectual property rights in China. It remains with Ti-Al-Sn-Zr-Mo-Cr-Nb-x series of 1100MPa intensity level. It has high strength, good toughness and fine damage tolence.In this paper, there are four cooling methods after heat treatment:furnace cooling, package cooling, air cooling and water cooling. The result showed that samples of furnace cooling and package cooling have high strength and high toughness contrast with the samples of air cooling and water cooling. Microstructure of TC21 alloy is influenced by cooling rate after heat treatment. Percentage of primary a phase increasing when cooling rate slowing down,βmatrix decreasing inβphase and solution treating and a+p heat treatment.Thick lamellar can be acquired in FC after heat treatment, the value of KIC is large, average is 96 MPam1/2. As fast cooling rate of package cooling, the thickness of a lamellar and a bunchiness are smaller than samples of furnace cooling. Value of toughness of samples of package cooling is lower, average is 73 MPam1/2. The KIC value is minimum when thickness of a lamellar is 1.3μm.Strength of TC21 alloy decreasing when percentage of primary a phase increasing, and it has small affect onβgrain size; plastic of TC21 alloy increasing when percentage of primary a phase increaing, decreasing whenβgrain size increasing. |
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