块体非晶合金压缩变形研究进展

Review on compressive deformation of bulk metallic glasses

在约化压缩变形温度t=Tg／Tg为77K／Tg≤tr〈trel、tr≤tr〈trc2和trc2≤tr〈Tx／Tg时，一般块体非晶合金的压缩变形行为分别对应不均匀脆性断裂、非牛顿流变和牛顿流变；当应变速率约为10S时，临界约化压缩变形温度trcl在0．839～0．920之间，trc2=1．011；随着应变速率的降低，块体非晶合金由不均匀的脆性断裂转变为非牛顿流变的frcl、由非牛顿流变转变为牛顿流变的trc2均降低。低tr压缩变形试样表面的剪切带特征明显，但高t，压编变形由于均匀变形和热影响作用使剪切带不明显，且块体非晶合金的塑性随剪切带数量的增加而提高；随着tr的升高，块体非晶合金的断口显微组织演化过程分别为复杂不均匀的脉状纹络、较均匀的脉状纹络、熔滴状和岩浆流状组织。另外在极低约化压缩温度tr下Ni60Pd20P17B3和Ti40Zr25Ni3Cu12Be20块体非晶合金表现出非牛顿流变行为。非晶在一定温度的压缩变形会导致部分或所有非晶纳米晶化。

In this paper, the compressive deformation behavior, samples surfaces and fracture microstructure characteristics have been reviewed at different temperatures and strain rates for bulk metallic glasses （BMGs）. BMGs behave like inhomogeneous brittle fracture, non-Newtonian fluid and Newtonian fluid mode respectively at reduced compressing temperature tr=T/Tg ranging of 77 K/Tg≤tr〈trcl . trcl≤tr〈trc2 and trc2≤tr〈Tx/Tg. When strain rate was about 10^-4 S^-1 , normally trcl =0. 839-0. 920 and trc2 =1. 011. With the strain rate decrea- sing, the critical reduced compressive temperatures trcl （changing from inhomogeneous brittle fracture mode to non-Newtonian fluid one） and trc2 （from non-Newtonian fluid one to Newtonian fluid one） were decreased. At low tr, plasticity of BMGs increased with the number of shear bands, which were obvious on the samples sur- faces, but at high t r they were even unobserved because of homogeneous deformation and heat. With t r increas- ing, fracture microstructure characteristics changed from complex and inhomogeneous vein-like pattern to hom- ogeneous one, then to droplets, or lava-flow pattern. In addition, Ni60Pd20Pl7B3 BMG and Ti40Zr25Ni3Cu12Be20 BMG behaved like non-Newtonian fluid mode during compressing at tr =0. 127-0. 503. Finally, this paper also discussed the phenomenon of nanocrystallization during the compression deformation.