Rapid Cooling Preparation Of Al-Cu-Zn System Alloy Material And Study On Microstructure Refinement

The method of rapid cooling can result in rapid solidification of alloy materials at high speed.This method can reform the structures of alloys,and improve properties.In the research of this dissertation,samples with diameters of 5 mm,8 mm and 10 mm were casted through a rapid cooling method,whose compositions were Al₆₃Cu₂₇Zn₁₀,Al₅₆Cu₂₄Zn₂₀,Al₄₉Cu₂₁Zn₃₀,Al₄₂Cu₁₈Zn₄₀, Al₄₂Cu₁₈Zn_30.0Sn_10.0,Al₄₅Cu₁₉Zn_31.0Sn_5.0 and Al₄₉Cu₂₁Zn_17.5Sn_12.5,respectively. The structures and compositions of samples were studied by metallurgical microscopy,X-ray diffraction(XRD),Differential Scanning Calorimetry(DSC), respectively.Meanwhile,the thermodynamics properties of samples were analysised by DSC,and the hardness are tested by sclerometer.The method of rapid cooling has the best effection on structures refinement of samples with diameter of 5mm by the Micrograph of the samples with diameter of 5mm,8mm and 10mm It has an same phenomena in every kind of compositions.The bigger size of samples,the worse effection they has.It is known that this method could refine the grains of samples,and restrain the phase in alloy form the shape of dendrite.This contributes to form the shape of smaller unit cell.Therefore,the shape of structure could be changed,and distribution of the compositions in alloys is prone to uniformity.It is can be concluded that Al₆₃Cu₂₇Zn₁₀,Al₅₆Cu₂₄Zn₂₀,Al₄₉Cu₂₁Zn₃₀ and Al₄₂Cu₁₈Zn₄₀ contain the phases ofα-Al,Al₂Cu and Al_4.2Cu_3.2Zn_0.7 by the XRD test,as well as Al₄₂Cu₁₈Zn_30.0Sn_10.0, Al₄₅Cu₁₉Zn_31.0Sn_5.0 and Al₄₉Cu₂₁Zn_17.5Sn_12.5 contain the phases ofα-Al,Al₂Cu, Al_4.2Cu_3.2Zn_0.7 and Al₃Cu₁₂Sn.The proportion ofα-Al phase is higher in all samples than that of Al_4.2Cu_3.2Zn_0.7 phase and Al₃Cu₁₂Sn phase. Exothermic peak can be observed in all samples by DSC curve.This shows the existence of metastable phase.The Al_4.2Cu_3.2Zn_0.7 phase in Al₆₃Cu₂₇Zn₁₀, Al₅₆Cu₂₄Zn₂₀,Al₄₉Cu₂₁Zn₃₀,Al₄₂Cu₁₈Zn₄₀ and the Al_4.2Cu_3.2Zn_0.7 phase,Al₃Cu₁₂Sn phase in Al₄₂Cu₁₈Zn_30.0Sn_10.0,Al₄₅Cu₁₉Zn_31.0Sn_5.0,Al₄₉Cu₂₁Zn_17.5Sn_12.5 are unsteady by analyzing.The unsteady phase can be changed under a certain temperature.Rapid cooling can refine the crystal structure of alloy samples,bring more intergranular interphase,and enhance the ability of resist outside force.This could improve the hardness of materials.It can be conclude that the samples with diameter of 5 mm have the biggest hardness,the samples with diameter of 8 mm take second place,the samples with diameter of 10 mm and natural cooling samples have lowest hardness by measuring the hardness of materials.The method of rapid cooling can improve the hardness value of Al-Cu-Zn system at least 10%from the data.