粉末冶金材料科学与工程
粉末冶金材料科學與工程
분말야금재료과학여공정
POWDER METALLURGY MATERIALS SCIENCE AND ENGINEERING
2014年
4期
530-537
,共8页
张昊%赵忠民%张龙%尹德军
張昊%趙忠民%張龍%尹德軍
장호%조충민%장룡%윤덕군
TiC-TiB2复合陶瓷%超高重力场%燃烧合成%组织均质性%断裂行为
TiC-TiB2複閤陶瓷%超高重力場%燃燒閤成%組織均質性%斷裂行為
TiC-TiB2복합도자%초고중력장%연소합성%조직균질성%단렬행위
TiC-TiB2 composite%ultrahigh gravity field%combustion synthesis%microstructure homogeneity
采用超高重力场燃烧合成工艺，并从500 g 到2500 g每间隔500 g 依次增大超重力场加速度，制备系列TiC-TiB2凝固陶瓷。经XRD、FESEM和EDS分析，发现陶瓷显微组织均由片晶的TiB2基体相、不规则的TiC第二相及少量的Al2O3夹杂与Cr基金属相组成。增大超重力场加速度，反应熔体内部各组份之间的对流(Stokes)加强，可加快Al2O3液滴的上浮与分离，促进TiC-TiB2-Me液相成分均匀化，使陶瓷显微组织得以细化，且当超重力场加速度超过2000 g 时，出现TiB2片晶厚度小于1μm 的超细晶组织，同时随陶瓷基体上Al2O3夹杂量降低、TiB2片晶异常长大弱化，陶瓷组织均匀性提高。经FESEM断口形貌与裂纹扩展观察，发现TiB2基体相的裂纹桥接与拔出，并耦合晶间 Cr 基延性相增韧构成陶瓷的复合增韧机制，且随超重力场加速度增大，陶瓷的致密性与组织均质性得以提升，不仅促进TiB2基体相裂纹桥接与拔出，而且可增大Cr基延性对陶瓷增韧的贡献，使得陶瓷弯曲强度与断裂韧性分别同时达到最大值(975±16) MPa和(16.8±1.2) MPa·m1/2。
採用超高重力場燃燒閤成工藝，併從500 g 到2500 g每間隔500 g 依次增大超重力場加速度，製備繫列TiC-TiB2凝固陶瓷。經XRD、FESEM和EDS分析，髮現陶瓷顯微組織均由片晶的TiB2基體相、不規則的TiC第二相及少量的Al2O3夾雜與Cr基金屬相組成。增大超重力場加速度，反應鎔體內部各組份之間的對流(Stokes)加彊，可加快Al2O3液滴的上浮與分離，促進TiC-TiB2-Me液相成分均勻化，使陶瓷顯微組織得以細化，且噹超重力場加速度超過2000 g 時，齣現TiB2片晶厚度小于1μm 的超細晶組織，同時隨陶瓷基體上Al2O3夾雜量降低、TiB2片晶異常長大弱化，陶瓷組織均勻性提高。經FESEM斷口形貌與裂紋擴展觀察，髮現TiB2基體相的裂紋橋接與拔齣，併耦閤晶間 Cr 基延性相增韌構成陶瓷的複閤增韌機製，且隨超重力場加速度增大，陶瓷的緻密性與組織均質性得以提升，不僅促進TiB2基體相裂紋橋接與拔齣，而且可增大Cr基延性對陶瓷增韌的貢獻，使得陶瓷彎麯彊度與斷裂韌性分彆同時達到最大值(975±16) MPa和(16.8±1.2) MPa·m1/2。
채용초고중력장연소합성공예，병종500 g 도2500 g매간격500 g 의차증대초중력장가속도，제비계렬TiC-TiB2응고도자。경XRD、FESEM화EDS분석，발현도자현미조직균유편정적TiB2기체상、불규칙적TiC제이상급소량적Al2O3협잡여Cr기금속상조성。증대초중력장가속도，반응용체내부각조빈지간적대류(Stokes)가강，가가쾌Al2O3액적적상부여분리，촉진TiC-TiB2-Me액상성분균균화，사도자현미조직득이세화，차당초중력장가속도초과2000 g 시，출현TiB2편정후도소우1μm 적초세정조직，동시수도자기체상Al2O3협잡량강저、TiB2편정이상장대약화，도자조직균균성제고。경FESEM단구형모여렬문확전관찰，발현TiB2기체상적렬문교접여발출，병우합정간 Cr 기연성상증인구성도자적복합증인궤제，차수초중력장가속도증대，도자적치밀성여조직균질성득이제승，불부촉진TiB2기체상렬문교접여발출，이차가증대Cr기연성대도자증인적공헌，사득도자만곡강도여단렬인성분별동시체도최대치(975±16) MPa화(16.8±1.2) MPa·m1/2。
By increasing the acceleration of high gravity field from 500 g to 2 500 g at intervals of 500 g, a series of solidified TiC-TiB2 were prepared by combustion synthesis in high gravity field. XRD, FESEM and EDS results show that the ceramics are comprised of TiB2 platelets as the primary phases, irregular TiC grains as the second phases, a few of Al2O3 inclusions and Cr-based metallic phases. Because of the enhanced Stokes flow in mixed melt with increasing acceleration in high gravity field, Al2O3 droplets are promoted to float up and separate from TiC-TiB2-Me liquid while constitutional distribution became more and more uniform in TiC-TiB2-Me liquid, resulting in not only the sharply-reduced Al2O3 inclusions in the solidified ceramic but also the achievement in refinement of the solidified microstructure. As the high-gravity acceleration exceeds 2 000 g, ultrafine-grained microstructure is obtained with TiB2 platelets in thickness smaller than 1 μm, resulting in the improvement of microstructure homogeneity. FESEM fractographs and FESEM images of crack propagation paths show that the procedure of toughening ceramic is achieved by coupling crack bridging and subsequent pullout by TiB2 platelets with ductile-phase-induced toughening by Cr-based intercrystalline phases. With increasing high-gravity acceleration, densification and homogeneity of the ceramics increase which not only promotes crack bridging and pullout of TiB2 matrix, but also increases the contributions of Cr-based ductile phases to toughening ceramic. The maximum values of flexural strength and fracture toughness ((975±16) MPa and (16.8±1.2) MPa·m1/2, respectively) of the solidified TiC-TiB2 composite are obtained in current experiment.
