Ti-7Cu合金半固态变形行为研究

发布时间：2019-01-28 08:43

【摘要】：钛合金凭借独有的特性,在航空航天,石油能源,生物医用等领域的起着重要作用。由于钛合金加工困难且成本较高,导致了与钛相关的产品价格居高不下。1970年半固态成形技术被提出以来,已经在镁铝及其合金中迅速发展,钢铁材料也在探索中。而钛铜合金中,除课题组等研究了Ti14,Ti230合金的半固态变形行为及力学性能之外,其他人很少涉及。因此,开展Ti-7Cu合金的半固态变形技术的研究,为钛合金半固态成形技术提供了理论基础和科学依据。本文以铸态Ti-7Cu合金为研究对象,在热模拟试验机(Gleeble3500)上进行了不同工艺参数条件的半固态变形试验,变形温度为:1223K,1273K,1373K,1473K。变形速率为:0.005s-1,0.05s-1,0.5s-1,5s-1。变形程度均为50%。通过获得不同工艺参数条件的应力应变曲线,分析了合金的半固态变形行为,建立了合金在1223K-1473K区间的本构方程,计算了不同参数下合金的变形激活能,结合不同半固态温度,变形速率下的变形组织,探讨了合金的变形机制。通过绘制合金不同应变下的热加工图,确定了合金的加工安全区和加工危险区。Ti-7Cu合金的半固态变形试验结果表明:半固态变形过程中,Ti-7Cu合金的流变应力有变形温度和变形速率的敏感性;流变应力随温度的升高和应变速率的降低而减小,随温度的降低和应变速率的升高而增大,在0.5s-1-5s-1范围内,流变应力增幅最大;在1223K-1473K区间内建立的本构方程,较好的符合Arrhenius双曲正弦关系;变形激活能的大小主要由变形温度和流变应力的共同决定;当温度高于1273K时,合金晶界处逐步析出液相,变形机制由固相粒子塑性变形(PDS)转变为固相粒子滑移(SS)或者固液相混合流动机理(FLS),当温度升高至1323K-1373K,变形机制发生了较大的变化;不同变形参数下,各个变形机理所占比例不尽相同;通过合金的热加工图,确定出了温度在(1543K-1598K),应变速率在(0.0025s-1-10s-1)区域会发生动态再结晶,属于加工安全区域。温度为(1498K-1583K),应变速率为(10s-1-100s-1)属于加工失稳区,温度为(1473K-1543K),应变速率为(3×10-5s-1-10-3s-1)和温度(1643K-1773K),应变速率为(3×10-5s-1-3×10-4s-1)的区域容易出现超塑性或开裂现象。
[Abstract]:Titanium alloys play an important role in aerospace, petroleum energy, biomedical and other fields with their unique characteristics. Because of the difficulty of processing and high cost of titanium alloys, the price of titanium related products is high. Since the semi-solid forming technology was put forward in 1970, it has been developed rapidly in magnesium, aluminum and its alloys, and the iron and steel materials are also being explored. In Ti-Cu alloys, except for the study of semi-solid deformation behavior and mechanical properties of Ti14,Ti230 alloys, few others have been involved. Therefore, the research on semi-solid deformation technology of Ti-7Cu alloy provides theoretical and scientific basis for semi-solid forming technology of titanium alloy. In this paper, the semi-solid deformation test of as-cast Ti-7Cu alloy was carried out on a thermal simulation testing machine (Gleeble3500) with different technological parameters. The deformation temperature was 1223K / 1273K, 1373K / 1373K / 1473K. The deformation rate is 0.005s-1, 0.05s-1, 0.5s-1and 5s-1. The degree of deformation is 50%. By obtaining the stress-strain curves of different process parameters, the semi-solid deformation behavior of the alloy is analyzed, the constitutive equation of the alloy in the 1223K-1473K region is established, and the deformation activation energy of the alloy under different parameters is calculated. The deformation mechanism of the alloy at different semi-solid temperature and deformation rate was discussed. By drawing the hot working diagram of the alloy under different strain, the processing safety zone and the processing dangerous area of the alloy are determined. The results of semi-solid deformation test of Ti-7Cu alloy show that: in the process of semi-solid deformation, The rheological stress of Ti-7Cu alloy is sensitive to deformation temperature and deformation rate. The rheological stress decreases with the increase of temperature and the decrease of strain rate, and increases with the decrease of temperature and strain rate. In the range of 0.5s-1-5s-1, the increase of rheological stress is the largest. The constitutive equation established in the 1223K-1473K region accords well with the Arrhenius hyperbolic sinusoidal relationship, and the magnitude of the deformation activation energy is mainly determined by the deformation temperature and the flow stress. When the temperature is higher than 1273K, the liquid phase is gradually precipitated at the grain boundary, and the deformation mechanism changes from solid particle plastic deformation (PDS) to solid particle slip (SS) or solid-liquid mixture flow mechanism (FLS), when the temperature rises to 1323K-1373K. The deformation mechanism has changed greatly; Under different deformation parameters, the proportion of each deformation mechanism is different. Through the hot working diagram of the alloy, it is determined that dynamic recrystallization occurs in the region of (1543K-1598K) and strain rate (0.0025s-1-10s-1), which belongs to the safe region of processing. The temperature is (1498K-1583K), the strain rate is (10s-1-100s-1) belongs to the processing instability region, the temperature is (1473K-1543K), the strain rate is (3 脳 10-5s-1-10-3s-1) and the temperature (1643K-1773K). The region with strain rate of (3 脳 10-5s-1-3 脳 10-4s-1) is prone to superplasticity or cracking.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.23

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