(Cu

47

Zr

45

Al)8)

98.5

Y

1.5

bulk metallic glass composites（BMGCs）with different crystallinity were prepared by copper mold casting and isothermal annealing treatment

and the relationship between microstructures and mechanical properties were investigated.The results indicate that the crystallization volume fraction（V

f

）is increased with annealing temperature increase.The process of phase transition is presented as follows:Am（amorphous state）→ Am+Cu

10

Zr

7

→Am+Cu

10

Zr

7

+AlCu

2

Zr+Al

2

Zr.The precipitation strengthening effect largely improves the microhardness of the alloy

and the maximum value of 691 HV can be observed after annealing at 760 Kfor 20 min.The fracture strength of the alloy is increased firstly and then decreased with the increase of annealing temperature.The fracture strength of the alloy reaches the maximum value of 1 950 MPa after isothermal annealing at 680 K.SEM of fracture surfaces reveals a transition of fracture characteristics from the ductile-brittle mixed fracture mode to a cleavage brittle manner with further annealing.The experimental results show that the mechanical properties of Cu-based BMGCs can be controlled by adjusting annealing process parameters

such as annealing temperature and annealing time.