汽车盘式制动衬片热压模设计

分析了汽车盘式制动嚣零件的工艺性，对其成形制造工艺、衬片模具结构及其设计、衬片模具的选材及主要零部件的制造加工要点、衬片模具的工作过程及使用情况等作了系统地介绍。     

RELATIONSHIP OF THE PROPERTIES OF HOT－PRESSING C－BC_4－SiC COMPOSITE WITH THE CONTENT OF ADDITIVE Al

ＲＥＬＡＴＩＯＮＳＨＩＰＯＦＴＨＥＰＲＯＰＥＲＴＩＥＳＯＦＨＯＴ－ＰＲＥＳＳＩＮＧＣ－ＢＣ_４－ＳｉＣＣＯＭＰＯＳＩＴＥＷＩＴＨＴＨＥＣＯＮＴＥＮＴＯＦＡＤＤＩＴＩＶＥＡｌ￥Ｈｕａｎｇ，Ｑｉｚｈｏｎｇ；Ｔａｎ，Ｐｉｎｇ；Ｙａｎｇ，Ｑｉａｏｑｉｎ＋；Ｈ?..     

Synthesis and properties of bulk nanocrystalline Mg2Si through ball-milling and reactive hot-pressing

1 Introduction The intermetallic compound Mg2Si is useful as strengthening phase in the metal matrix composites (MMC) due to its low density (1.99 g/cm3) and high strength-to-mass ratio[1?5]. It is also promising as a basic material for thermoelectric ene…     

钛硅铝碳层间固溶体陶瓷的超结构现象

研究了钛硅铝碳（ Ti3Siy-xAlxCz）层间固溶体陶瓷材料的超结构现象。结果发现，用热压Ti、Si、Al和C（石墨）混合粉末原位反应合成的Ti3Si0．9Al0.3C1.93和Ti3Si0.8Al0.4C1.93层间固溶体块体样品的X射线衍射（XRD）谱中[00L]晶面的衍射峰极其微弱，只有[008]面有一个小的衍射峰，[002]、[004]和[006]面几乎没有衍射峰存在，而该块体样品的粉末的X射线衍射谱中所有[00L]晶面的衍射峰均存在。这种超结构现象表明，用热压原位反应合成的Ti3Si0．9Al0．3C1.93和Ti3Si0.8Al0.4C1.93实为层间无序固溶体。由于内应力的释放，取自该块体样品的粉末发生了从无序到有序的转变，所以粉末的X射线衍射谱中显现出强的[00L]面衍射峰。这种超结构相可能对Ti3Si0.9Al0.3C1.93和Ti3Si0．8Al0．4C1.93块体的性能产生重要影响。     

Consolidation of Cr3C2 doping WC–1TiN–5MgO micro–nano composites by two-step sintering

The effect of Cr₃C₂ additions on WC–1TiN–5MgO composites by two-step hot-pressing sintering (heated to 1750°C and then immediately cooled to 1575°C with a soaking time of 60?min under a sintering pressure of 50?MPa) was comprehensively investigated. The microstructure was characterized by means of scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffractometry (XRD). Mechanical properties, such as hardness, transverse rupture strength, and fracture toughness, were measured. The experimental results show that no η-phase or brittle phases such as W₂C were formed, and excellent mechanical properties were achieved for 0.6?wt.% Cr₃C₂ additions with a hardness of 24.76?GPa, a flexural strength of 1257.1?MPa, and a fracture toughness of 10.08?MPa?·?mm^1/2. Cr₃C₂ addition brought about an improvement in the sinterability and contributed to the homogeneous distribution of second phase nanosized MgO. Crack deflection and crack bridging are the major mechanisms contributing to the drastically enhanced flexural strength and fracture toughness.     

低温热压氮化硅的烧结机理

选择了一种MgO-Al_2O_3-SiO_2系统添加剂,能在1550℃的较低温度(约10wt％液相量,30MPa)将氮化硅材料热压致密化。由于氮化硅和碳纤维在此较低温度能够共存,从而使氮化硅有可能和碳纤维构成复合材料,以改善氮化硅的脆性。 本文研究了在1450—1650℃温度范围内,有液相存在的氮化硅的热压烧结机理和动力学。发现致密化过程与Kingery液相烧结机理较为吻合。过程溶解-扩散-再沉淀阶段的动力学可用ΔL/L_0=K·t~(1/n)表述。温度的差异明显地影响致密化速率;压力和液相量对致密化速率亦有较大影响。     

热压工艺对SiCf/Ti复合材料界面反应层生长影响的数值模拟

提出一个热-力-扩散-反应强耦合相场模型来研究热压烧结制备工艺对连续碳化硅纤维增强钛基复合材料中金属间化合物生长规律的影响。模拟结果表明,在两种不同温度下各个界面反应层(Ti₃SiC₂/Ti₅Si₃C_x/Ti₅Si₃C_x+TiC/TiC)的厚度生长与试验值吻合较好。增大外加压力能促进界面层厚度的生长,但对其中抗拉强度最低的Ti₅Si₃层的生长起显著的抑制作用,同时使各界面反应层由周向拉应力状态逐渐转变为压应力。温度的升高使断裂韧度最大的Ti₃SiC₂层厚度增大,但也使总界面层和Ti₅Si₃层的厚度增加。因此,在制备工艺上适当增加压力并选择合适的温度,得到厚度适宜的界面反应层的同时,尽可能使Ti₅Si₃层变薄和Ti₃Si...     

Densification,microstructure, elastic and mechanical properties of reactive hot-pressed ZrB2–ZrC–Zr cermets

In this study, cermets composed of zirconium diboride and zirconium carbide with intergranular zirconium were sintered by reactive hot-pressing. Relative density exceeding 97% was obtained for the sintered cermets having four distinct compositions varying in concentration of excess Zr. Their densification behaviour was examined by monitoring displacement during sintering. The microstructure was characterized by scanning electron microscopy and X-ray diffraction, and the elastic and mechanical properties were evaluated at room temperature. The effects of Zr concentration on the densification and mechanical properties were assessed. The ZrB₂ and ZrC micron-grains coarsened with increasing amount of Zr starting material. In addition, the cermets exhibited high flexural strength (546–890 MPa) and fracture toughness (6.63–10.24 MPa m^1/2), which simultaneously increased with increasing Zr concentration. However, the elastic moduli and hardness (11–18 GPa) decreased with increasing Zr. The shear modulus and Young's modulus were in the range of 150–190 GPa and 360–440 GPa, respectively.     

In situ reaction and solid solution induced hardening in (Ti,Zr)B2-(Zr,Ti)C composites

(Ti,Zr)B₂ - (Zr,Ti)C ceramics were synthesized by reactive hot-pressing and solid solution coupling effect using ZrB₂ and TiC powders as starting materials. Effects of sintering temperature on phase relations, microstructure and mechanical properties were reported. The equimolar ZrB₂ and TiC reactants ensured a complete in situ reaction to form (Ti,Zr)B₂ and (Zr,Ti)C solid solutions. The (Ti,Zr)B₂ - (Zr,Ti)C composite sintered at 1750°C was fully densified, and exhibited a high hardness of 29.1 GPa due to fine-grain hardening and solid solution hardening. The optimized comprehensive mechanical properties such as a hardness of 27.9 GPa, a strength of 705 MPa and an indentation fracture toughness of 5.3 MPa m^1/2 were achieved in (Ti,Zr)B₂ - (Zr,Ti)C composites sintered at 1800°C for 1 hour.