"半固态/液态"双金属复合铸锭的界面凝固行为研究

The interface with metallurgic bonding can be obtained by the liquid/liquid compound technology. And this technology became a important preparation method for the bimetallic composites. But the development and application of the technology have be hinder by the interface defects of uncontrollable interface width and discontinuous interface. And the semi-solid metal slurry have the characteristics of high viscosity and low temperature. If the extent of convection and disffusion between the semi-solid metal slurry and the molten metal was decreased, the controllable interface width and continuous interface would be realized. In this project, a kind of AZ91D/6061 bimetallic composites ingots with semi-solid microstructures will be prepared by continuous casting with the semi-solid slurry and the molten metal pouring (semi-solid/liquid pouring continuous casting). Otherwise, the interface with high strength, zero defect, continuous stability and controllable interface width will be obtained by the technology. And then, the relationship between microstructure characteristics, processing parameters and interface morphology will be preferential investigated, the bonding mechanism of the bimetallic composites prepared by the semi-solid/liquid pouring continuous casting technology will be studyed. If this project was implemented, a new technology for the bimetallic composites would be developped and the formation theory of the metallurgic bonding interface would be expanded.

液/液复合技术因可实现牢固冶金结合的界面，而成为制备双金属复合材料的重要手段；但其界面宽度可控性和稳定性差，阻碍了其技术的进一步发展与应用。而低温的半固态金属浆料具有较高的黏度，与高温金属熔体的对流、扩散能力相对较低，则有利于控制两者形成的冶金结合界面宽度和连续稳定性。本项目旨在利用半固态金属浆料与液态金属熔体同时浇注，并连续铸造出具有"半固态显微组织/枝晶组织"特征的AZ91D/6061双金属复合铸锭，其界面宽度易调控，且界面强度高、无缺陷，连续稳定；重点研究半固态金属浆料特性、铸造工艺参数与界面形态的相互关系，探讨"半固态/液态"复合技术制备双金属复合材料的界面凝固机理，为"半固态/液态" 金属同时浇注连续铸造技术制备高性能双金属复合材料提供理论依据和关键技术。本项目的实施不但为制备双金属复合材料开辟一条新途径，而且丰富了冶金界面的形成理论，还将深化对金属材料凝固规律的认识。

双金属复合材料因综合了两种以上金属的优势，具有优势互补效应，可在极端恶劣环境条件下工作，广泛应用于船舶、汽车、电力电子、石油化工、航空航天等领域。目前，双金属复合材料制备主要有液/液复合、固/液复合、固/固复合等技术。而液/液复合技术因可实现牢固冶金结合的界面，而成为制备双金属复合材料的重要手段；但其界面宽度可控性和稳定性差，阻碍了其技术的进一步发展与应用。而低温的半固态金属浆料具有较高的黏度，与高温金属熔体的对流、扩散能力相对较低，则有利于控制两者形成的冶金结合界面宽度和连续稳定性。本项目利用半固态金属浆料与液态金属熔体同时浇注，并连续铸造出具有“半固态显微组织/枝晶组织”特征的AZ91D/6061双金属复合铸锭，其界面宽度易调控，且界面强度高、无缺陷，连续稳定；重点研究半固态金属浆料特性、铸造工艺参数与界面形态的相互关系，探讨“半固态/液态”复合技术制备双金属复合材料的界面凝固机理。复合界面的复合机理或凝固行为是：熔融复合与扩散复合相结合；复合界面主要分为三个区域：Ⅰ区（与外层6061合金相接，以Al3Mg2相为主），Ⅱ区（界面中间部位，以Al12Mg17相为主），Ⅲ区（与内层AZ91D合金相接，以Al12Mg17+δ-Mg相为主）。本项目可为“半固态/液态” 金属同时浇注连续铸造技术制备高性能双金属复合材料提供理论依据和关键技术。本项目的实施不但为制备双金属复合材料开辟一条新途径，而且丰富了冶金界面的形成理论，还将深化对金属材料凝固规律的认识。