Effect of Dy addition on microstructure and mechanical properties of Mg-4Y-3Nd-0.4Zr alloy

Minor Dy element was added into a Mg?4Y?3Nd?0.4Zr alloy,and its effects on the microstructure and the mechanicalproperties at elevated temperatures were investigated.Scanning electron microscope(SEM)and transmission electron microscope(TEM)were used to observe the microstructures.The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg?REphases were Mg5RE and Mg3RE17,respectively,and distributed mainly along grain boundaries.After a solution treatment,theeutectic Mg5RE phases were dissolved into the matrix,whereas the Mg3RE17compound still remained.After peak aging,fineMg?RE phases were precipitated homogeneously within the matrix of the alloys containing Dy.Dy addition can result in asignificant improvement in the tensile strength at both room and elevated temperatures,and a slight decrease in the elongation.

Microstructure and elevated-temperature tensile properties of differential pressure sand cast Mg-4Y-3Nd-0.5Zr alloy

The microstructures of an Mg-4Y-3Nd-0.5Zr alloy by differential pressure casting were investigated using scanning electron microscopy （SEM） and transmission electron microscopy （TEM）, and its tensile deformation behavior was measured using a Gleeble1500D themo-simulation machine in the temperature range of 200 to 400 ℃ at initial strain rates of 5×10^-4 to 10^-1 s^-1. Results show that the as-cast microstructure consists of primary α-Mg phase and bone-shaped Mg5RE eutectic phase distributed along the grain boundary. The eutectic phase is dissolved into the matrix after solution treatment and subsequently precipitates during peak aging. Tensile deformation tests show that the strain rate has little effect on stress under 300 ℃. Tensile stress decreases with an increase in temperature and the higher strain rate leads to an increase in stress above 300 ℃. The fracture mechanism exhibits a mixed quasi-cleavage fracture at 200 ℃, while the fracture above 300 ℃ is a ductile fracture. The dimples are melted at 400 ℃ with the lowest strain rate of 10^-4 s^-1.

Elastic deformation behavior of CuZrAlNb metallic glass matrix composites with different crystallization degrees

The room temperature brittleness has been a long standing problem in bulk metallic glasses realm.This has seriously limited the application potential of metallic glasses and their composites.The elastic deformation behaviors of metallic glass matrix composites are closely related to their plastic deformation states.The elastic deformation behaviors of Cu48-xZr48Al4Nbx（x=0,3at.%）metallic glass matrix composites（MGMCs）with different crystallization degrees were investigated using an in-situ digital image correlation（DIC）technique during tensile process.With decreasing crystallization degree,MGMC exhibits obvious elastic deformation ability and an increased tensile fracture strength.The notable tensile elasticity is attributed to the larger shear strain heterogeneity emerging on the surface of the sample.This finding has implications for the development of MGMCs with excellent tensile properties.