The Effect Of The Additionl Element Be On The ZrCuAl Glass Forming Ability And Mechanical Properties

In this thesis, the effect of the additional element Be on the glasses forming abilityand thermal stability of(Zr₄₃Cu₅₀Al₇)（100-x）_Be_xand(Zr₄₆Cu₄₂Al₇Y₅)（100-x）_Be_xbulk metallicglasses have been investigated. The bulk metallic glasses samples were prepared by usingnon-consumable arc melting and copper mold suction casting technique. The crystalstructure of the samples was invesigated by XRD, the thermal dynamic properties weremeasured by DSC, according to the Miedema model the galsses formation enthalpy werecalculated. The digital micro-hardness, universal material testing machine and scanningelectron micro analyzing （SEM） were applied to characterize the Vickers-hardness,compression performance and fractured morphologies of bulk metallic glasses.The effects of alloying element Be on the GFA of the Zr₄₃Cu₅₀Al₇and Zr₄₆Cu₄₂Al₇Y₅alloys were discussed. It was found that5at%Be addition can greatly improve the GFA ofZr₄₃Cu₅₀Al₇alloy and the cirtical size were increased from3mm to more than4mm,5at%Be addition can greatly improve the GFA of Zr₄₆Cu₄₂Al₇Y₅alloy as well and the cirticalsize were increased form4mm to more than6mm. Meanwhile, the thermodynamiccriterion Trgor γ are effective in evaluating the GFA of the (Zr₄₃Cu₅₀Al₇)（100-x）_Be_xand(Zr₄₆Cu₄₂Al₇Y₅)（100-x）_Be_xglass forming systems. According to the Miedema model, theforming formation enthalpy of the (Zr₄₃Cu₅₀Al₇)（100-x）_Be_xand (Zr₄₆Cu₄₂Al₇Y₅)（100-x）_Be_xsystems was found both to be negative which is benefit to form metallic glasses.Crystallization kinetics study indicats that the glass transition and crystallizationbehavior showed the typical characteristic of kinetics．The process of the Zr₄₃Cu₅₀Al₇and(Zr₄₃Cu₅₀Al₇)95Be5contains one step of crystallization,and the effective activation energyof the phase transformation Ep₁is344KJ/mol,287KJ/mol respectively. The thermalstability of the former was better than the later The process of the Zr₄₆Cu₄₂Al₇Y₅and(Zr₄₆Cu₄₂Al₇Y₅)91Be9contains two step of crystallization,and the effective activationenergy of the phase transformation is Ep₁=356KJ/mol，Ep₂=251KJ/mol, Ep₁=303KJ/mol，Ep₂=305KJ/mol,respectively. Both have simmilar thermal stability.The plasticity and strength have no significant change with the x change in the(Zr₄₃Cu₅₀Al₇)（100-x）_Be_xthe (Zr₄₆Cu₄₂Al₇Y₅)（100-x）_Be_xsystem. The compressive strength Of the former ranges form1511to1774MPa, while that of the later ranges from1695to1979MPa. All of them have good mechanic properties.