钛合金复杂构件粉末体多向加载成形致密与组织调控研究

The multi-ram loading for the sintered compact can produce the integral metal parts with complex structures to near-net shapes with short process, but it is impossible for the traditional forge process to manufacture them. The complex integral metal parts manufactured can solve some problems resulted from the traditional powder forging, such as unsatisfactory density and poor density distribution, moreover can solve some problems resulted from hot isostatic pressing process, e.g. the high production cost. For the new multi-ram loading process with Ti-6A1-4V titanium alloy complex metal parts, the evolution regularities of the deformation physical fields in forming the parts , and the second includes the effect of pore structure on the flow stress in forming the parts will be researched. The effect of complex strain and temperature history of microstructure evolution and densification will be analyzed.The rule of globularization of sintering structure in forming the parts and the formation mechanism organizations of the tri-modal microstructure will be revealed ，the effect of the multi-ram loading conditions、 forming parameter、 cavity structure，etc.on metal flow and densification of typical components will be identified and the corresponding cavity design guidelines will be estabished，the characterization of powder forging variable physical property parameters and variable friction conditions ,and the collaborative control of density field and organization field are the two key technical problems to be made breakthrough， accurate forming ,fully dense and microstructure equitable distribution for the powder forging will be achieved，the method of multi-ram loading for titanium alloy powder complex parts to dense and microstructure control roundly in forming will be given.

烧结坯多向加载成形不仅能解决传统锻造无法成形复杂整体构件的问题，还可解决传统粉末冶金致密度不理想与热等静压成形成本昂贵等难题。针对Ti-6A1-4V合金复杂构件烧结坯多向加载成形新技术，主要研究多孔体成形过程物理场量演化规律，探明孔隙对多孔体流动应力的影响，探讨复杂应变与温度历史对微观组织演变以及致密化的作用，揭示烧结组织在成形过程中的球化规律以及三态组织形成机制，建立扩散和应力场耦合作用的致密化模型，明确多向加载条件、成形参数、型腔结构等对典型构件金属流动与致密化的影响并建立相应的型腔设计准则，突破粉末锻造变物性参数与变摩擦条件的表征、多孔体密度场与组织场的协同控制这两个关键技术难题，实现粉末锻件的精确成形、全致密和微观组织合理分布，提出钛合金复杂构件粉末多向加载过程成形致密和组织调控方法。

针对不同烧结工艺的多孔Ti-6Al-4V钛合金，研究了不同致密度试样在不同温度、速度下的热变形行为，建立了多孔钛合金流动应力模型。以弹性接触应力场为初始条件，建立了由表面扩散和应力场共同驱动的致密化分析模型。测定了不同致密度试样的泊松比、弹性模量、比热容、热传导系数与热锻摩擦系数，与全致密试样各项参数进行对比，实现了多孔试样物性参数与摩擦条件的表征，并利用有限元分析模型对表征模型进行了检验和完善。针对不同烧工艺的多孔Ti-6Al-4V钛合金坯料，采用不同的变形温度和变形速度，研究了多道次（不同的变形量）预锻变形对多孔体密度场演化的影响规律；以及烧结组织球化成等轴组织过程中变形程度、变形速率、变形温度等对组织演变的影响规律，并研究了多道次变形与热处理（不同道次变形量与热循环）所获得的各类（准）三态组织的形成机制。针对Ti-6Al-4V复杂构件（导弹隔框类零件），研究了多向加载对变形体成形过程中密度和组织的影响规律。针对制备的三态组织构件，提出了成形构件密度场与组织场调控方案，结合金属流动缺陷，根据构件成形尺寸与技术指标要求，确定了典型Ti-6Al-4V粉末构件成形方案与成形参数。