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Al2O3-W-Cr金属陶瓷挤压模具的制备与性能研究
【作者】 陈娇；
【导师】 罗兵辉；
【作者基本信息】 中南大学 ， 材料学， 2010， 硕士
【摘要】 本文针对白铜挤压成形模的要求,从提高模具材料的使用寿命出发,选用具有高硬度、耐磨损、耐高温、抗腐蚀、原料分布广泛的Al2O3为基体,采用热压烧结法制备了Al2O3-W-Cr复合陶瓷模具材料,研究了其力学性能、微观结构、强韧化机理、抗热震性能以及摩擦磨损行为,并利用有限元对Al2O3-W-Cr复合陶瓷材料挤压模具的工作状况进行分析,探讨陶瓷模具工作条件下的应力场和温度场的分布规律,得出如下结论：(1)研制的2种Al2O3-W-Cr(W%=19vol%,Cr%=19 vol%),(W%=15vol%,Cr%=15 vol%)复合陶瓷模具材料其抗弯强度分别为800 MPa和560 MPa,断裂韧性为9MPa·m1／2和13 MPa·m1／2。W和Cr金属粒子的加入极大改善了两种材料的抗热震性能,两种材料表现为热震断裂和热震损伤的混合模式,1号模具材料的临界热震温差AT为480℃,2号模具材料的临界热震温差△T为680℃。2号模具材料的抗热震参数R、和RⅣ均高于1号模具材料,分别为165℃,347×106μm与337℃,1256×106μm。(2)两种材料具有相似的磨损行为,摩擦系数随法向载荷的增大而降低、随摩擦时间的延长而升高,变化趋势均越来越缓慢；磨损过程是磨粒磨损、粘着磨损、疲劳磨损共同作用的过程。2号材料具有比1号材料更优良的抗磨性能。(3)采用Gleeble-1500热模拟试验机进行压缩试验,建立了Al2O3-W-Cr金属陶瓷的应力-应变本构方程为(4)利用有限元软件Deform-3D模拟了铜管挤压凹模的工作状况,对其应力场和温度场进行分析,挤压过程中应力场和温度场呈不均匀分布,越靠近模口处,温度越高,应力越大,模具外部应力值和温度都低于内部；模具表面和模口处容易产生磨损与失效,甚至在纵向开裂；针对这一失效特点,提出相应的改善方法。
【Abstract】 For the requirement of ceramic materials as the forming dies, composite ceramic die materials with high mechanical properties were fabricated with composite method by selecting alumina ceramics matrix which has excellent hardness, wear-resistance, high-temperature resistance, corrosion resistance and wide range raw materials. The strengthening and toughening mechanisms, microstructure, mechanical properties, friction and wear properties as well as thermal shock resistance of the ceramic die materials were investigated. To provide technical basis for the application of ceramic materials the working conditions of extrusion die were studied by the use of FEM. The results are as following:(1) The flexural strength and fracture toughness of the two composite ceramic materials are 800MPa,9MPa·m1/2 and560MPa,13 MPa·m1/2 respectively. The addition of metal particles W, Cr greatly improved the thermal shock resistance of the mold material, performed the mix mode of thermal shock facture and thermal shock damage. The critical thermal shock temperature of the two samples are 480℃and 680℃, respectively. The thermal shock parameter R, and RⅣof sample 2 were higher than sample 1, and R, and RⅣwere 165℃,347×106μm; 337℃,1256×106μm respectively.(2) Fracture toughness enhancement and optimization of structure lead to the improvement of wear resistance of Al2O3 mold material. The two materials proved the same trend, the friction coefficient decreases with the increases of load and increased with the increases of time; main friction mechanism were abrasive wear, adhesive wear, fatigue wear.(3) The high temperature deformation of Al2O3-W-Cr cermet was investigated by the high-temperature thermal simulation experiment; the stress-strain equation of Al2O3-W-Cr cermet was established as follows: (4) The stress status of the extrusion ceramic die for cup was analyzed by means of the Deform-3D FEM software, stress and temperature field were distributed uneven, mold withstand large tensile stress and high temperature, easy to failure in the mold surface. From mold design and mold making, provide improvements.