Study On Hot Deformation Behavior And Processing Map Of Laves Phase NbCr₂Alloy

Laves phase NbCr2base alloy is an intermetallic compound of close-packed topology，itsexcellent high temperature oxidation resistance and hot corrosion resistance make it havegreat potential in high temperature structural materials applications. Recently, there are manybasic research about toughness at room temperature, high temperature oxidation resistance,soft second phase toughening and alloying toughening of Laves phase NbCr2base alloysprepared by mechanical alloying and hot pressing. However, there is little research about theirhot deformation behavior and processing map at high temperature.By Gleeble isothermal constant strain rate compression experiment, this paper obtainedthe stress-strain curves of Cr-12Nb two phase NbCr2/Cr alloy and Cr-77.5Nb two phaseNbCr2/Nb alloy deformed under the conditions of high temperature from800to1200℃andthe strain rate from0.001to0.1s-1.The influence of deformation parameters includingtemperature、strain rate and strain on flow stress was also discussed in this paper.Within the experimental conditions, stress-strain curves of Cr-12Nb and Cr-77.5Nbnearly have the same change trend, the flow stress increases with the loss of the deformationtemperature or with the increase of strain rate, so does the peak stress. At800℃and1000℃,the stress-strain curve shows strain softening model, and at the same strain rate, strainsoftening phenomenon becomes less obvious as the temperature increases. At1200℃, thestress-strain curve shows approximately state flow model.According to the obtained data of stress-strain curves, the adaptability of Arrheniusequations for the two kinds of alloy were tested, the results show that the Arrhenius equationsare not suitable to describe the hot deformation behavior of Laves phase NbCr2base alloy,therefore on the basis of it constitutive relation models appropriate for Laves phase NbCr2base alloy were proposed, and the coefficients in the model were determined by stepwiseregression method, then appropriate constitutive relation were built up. Error analysis showsthat the identified constitutive relations have high precision, can satisfy the requirement ofengineering application.The processing maps of Cr-12Nb and Cr-77.5Nb alloy were built up at different strainsbased on dynamic material model and Murty and Prasad instability criterion. Throughanalysis and comparision, the practical processing should refer to the processing maps builtbased on Prasad instability criterion. The results show that: the better deformation parameterof Cr-12Nb is950℃~1170℃、0.001s-1~0.005s-1and1170~1200℃、0.01s-1~0.1s-1, the best parameter of the alloy is around1100℃、0.001s-1. The better deformation parameter ofCr-77.5Nb is925~1200℃、0.001s-1~0.006s-1, the best parameter of it is around1100℃、0.001s-1.