材料期刊网

在573 K,通过等通道转角挤压成功制备了7075 Al/AZ31复合板,并采用SEM、EDS、XRD和剪切实验研究了挤压道次及退火温度对复合板界面层组织和性能的影响及剪切断裂面的组成.结果表明:1道次等通道转角挤压制备的复合板界面处形成厚度为20μm均匀致密的扩散层,由Al3Mg2相和Mg17Al12相组成,Al3 Mg2相层厚(17 μm)是Mg17Al12相层厚(3μm)的5.6倍.2道次等通道挤压后,扩散层厚度无变化,但是出现了裂纹,剪切强度大幅下降,剪切断裂面发生在Al3Mg3相层.复合板界面层在473 K退火,扩散层厚度无变化,裂纹无改善,剪切强度略有提高;573 K退火,复合板扩散层中的Al3 Mg2相层和β-Mg17Al12相层均急剧增厚,微裂纹被焊合,剪切强度均大幅下降.在相同处理状态下,1道次ECAP复合板剪切强度均高于2道次ECAP复合板,473 K退火处理后,强度高出30.11％.573 K退火处理后,强度高出12.4％.故利用等通道转角挤压法制备7075Al/AZ31复合板,1道次比较合适,扩散层退火温度不宜超过473 K.

7075Al/AZ31 laminated composites were successfully fabricated by equal channel angular processing (ECAP) at 573 K.The effect of ECAP passes arid annealing temperature on microstructure evolution,phase constituent and bonding strength near the joining interface of the laminated composites was studied by means of scanning electron microscopy,X-ray diffraction and shear tests.The results indicate that diffusion layer with thickness of 20 μm is observed at the joining interface of the laminated composites prepared by one ECAP pass.The diffusion layer is mainly composed of Al3Mg2 and β-Mg17Al12 phases.After two ECAP passes,the change of the diffusion layer thickness is not obvious,while the formation of crack in the diffusion layer leads to the bonding strength decreasing.After annealing at 473 K,the thickness of the diffusion layer and the crack remains unchange,while the bonding strength increass slightly.However,with increasing the annealing temperature to 573 K,the thickness of the diffusion layer increases rapidly,and the bonding strength decreases.The laminated composite fabricated by one ECAP pass presents higher bonding strength than that of fabricated by two ECAP passes after annealing under the same condition.Therefore,the processing parameters of one pass ECAP and annealing at 473 K are recommended to fabricate the 7075A/AZ31 laminated composite plates.