半固态铜合金压缩变形液固两相变形协同性能及组织演变

Because of the existence of liquid-solid phase, deformation behaviors including rigid-plastic deformation, visco-plastic deformation, viscous flow and liquid segregation were occurred during the semisolid forming, which caused the composition segregation and inhomogeneous microstructure and affected the quality of the products. Therefore, the research of deformation behavior of semisolid metal has important significance on improving the microstructure and mechanical properties of semi-solid products. The SIMA method including multidirectional rolling and remelting is used to fabricate the semisolid copper alloy. The uniaxial compressive deformation behavior of semi-solid copper alloy is investigated by using the Gleeble thermal simulation method. The influence of process parameters on spherical grain is researched. The spheroidizing mechanism of the semisolid copper alloy fabricated by SIMA method is revealed. A control method for the preparation of uniform fine spherical microstructure is proposed. The relationship between process parameters and spherical grain is established. The thixotropic behavior, stress-strain and solid-liquid flow principle of the semisolid copper alloy during compression are researched. The effect of compression conditions on deformation coordination of solid-liquid phase is analyzed. The deformation coordination condition of solid-liquid phase is discussed. The effect of deformation conditions on solid-liquid microstructure evolvement of semisolid copper alloy is investigated. The evolvement principles of solid-liquid microstructure with different deformation conditions are determined. Finally, the compression deformation mechanism of semisolid copper alloy is revealed based the above research results. The research results can provides the theoretical basis for fabricating the semisolid copper alloy and rheoforming or thixoforming of copper alloy, which can enrich and develop the basic theory of semi-solid metal forming technology.

由于液固两相的存在，半固态金属成形会产生刚塑性变形、粘塑性变形、粘性流动、液固分离等变形行为，导致产生成分偏析、组织不均等缺陷，影响产品质量。因此，研究半固态金属变形行为对改善其产品组织和性能有重要意义。本项目采用多向轧制与重熔加热SIMA法制备半固态铜合金，利用Gleeble热模拟方法研究半固态铜合金单向压缩变形行为。研究制坯条件对球化组织的作用机制，分析球化组织的形成机理，提出制备均匀细小球化组织的控制方法，建立制坯条件与球化组织特征的定量关系；分析压缩变形半固态铜合金的触变行为、应力-应变和液固两相流动规律，阐述变形条件对液固两相变形协同性能的作用机制，探索液固两相协同变形条件；分析变形条件对液固两相形态和分布的作用机制，阐明液固两相组织演变规律，最终揭示半固态铜合金压缩变形机制。预期成果将为半固态铜合金坯料制备及其流变或触变成形提供理论基础，丰富和发展半固态金属成形技术的基础理论。

由于液固两相的存在，半固态金属成形会产生刚塑性变形、粘塑性变形、粘性流动、液固分离等变形行为，导致产生成分偏析、组织不均等缺陷，影响产品质量。因此，研究半固态金属变形行为对改善其产品组织和性能有重要意义。本项目以高熔点铜合金为研究对象，采用轧制变形和重熔工艺制备半固态铜合金坯料，利用Gleeble热模拟方法研究半固态铜合金压缩变形行为和微观组织演变。首先，研究了多向多道次冷轧及热轧对铜合金组织的影响，分析了冷轧与重熔、热轧与重熔制备的半固态铜合金组织形貌，结果表明：虽然冷/热轧与重熔工艺都能制备得到半固态铜合金组织，但热轧时铜合金坯料易开裂，导致其无法稳定制备得到理想的半固态铜合金，最终采用冷轧与重熔工艺制备半固态铜合金，并研究了变形量、重熔温度和保温时间对半固态铜合金微观组织的影响，揭示了半固态铜合金球化组织的形成机制，获得了液相率高、平均晶粒直径小以及形状因子小的半固态铜合金最佳制备工艺参数：冷轧变形量22%、重熔温度900℃、保温15-20min。其次，研究了半固态铜合金坯料压缩变形，分析了压缩过程中半固态铜合金液固两相的变形行为，研究了变形量、变形温度和应变速率对半固态铜合金应力-应变曲线的影响规律，构建了半固态铜合金压缩变形本构方程；再次，研究了单向压缩变形过程中半固态铜合金液固两相微观组织的演变，分析了压缩试样不同变形区固相颗粒形貌及大小、液相分布、物相及Sn元素在液固两相的分布，揭示了半固态铜合金压缩变形中液固两相演变规律；最后，探究了半固态铜合金挤压变形行为，分析并获得了挤压变形中半固态铜合金液固两相演变机制，包括固相颗粒塑性变形、液相流动、固相颗粒形貌及物相等，同时，获得了不同挤压工艺条件下半固态挤压铜合金力学性能。本项目的研究成果有望为半固态铜合金坯料制备及其流变或触变成形提供理论基础，拓展半固态技术在高熔点合金中的应用，丰富和发展半固态金属成形技术的基础理论。