(西安交通大學(xué) 金屬材料強(qiáng)度國(guó)家重點(diǎn)實(shí)驗(yàn)室,
西安 710049)
摘 要: 利用氣相化學(xué)反應(yīng)， 以H3BO3和CO(NH2)2作為BN源， 將納米BN包覆到Al2O3顆粒表面，經(jīng)熱壓燒結(jié)制備出高強(qiáng)韌可加工BN/Al2O3復(fù)合材料。 材料的三點(diǎn)彎曲強(qiáng)度隨BN含量的增加而緩慢降低， BN體積分?jǐn)?shù)為30% 時(shí)， 仍達(dá)到446MPa； 斷裂韌性隨BN含量的增加而得到顯著改善， 較單相氧化鋁陶瓷提高近一倍。 BN體積分?jǐn)?shù)大于20%時(shí)， 該復(fù)合材料可用WC鉆頭在普通臺(tái)式鉆床上鉆孔， 在小的軸向壓力（10N）下， 鉆孔速率大于1mm/min， 鉆孔邊緣平整， 沒(méi)有崩裂現(xiàn)象，內(nèi)壁光滑， 粗糙度RZ =（6±0.5）μm。 SEM觀察顯示，加工未帶來(lái)明顯的損傷。 材料優(yōu)異的力學(xué)性能及可加工性源自于基質(zhì)中均勻分布的細(xì)小h-BN的顆粒增韌機(jī)制及其易解理的層狀結(jié)構(gòu)特點(diǎn)。
關(guān)鍵字: 復(fù)合材料； 氧化鋁； 氮化硼；力學(xué)性能； 可加工性
（State Key Laboratory for Mechanical Behavior of Materials, Xi′an Jiaotong University,Xi′an 710049, China）
Abstract:BN/Al2O3 ceramic composites with fine BN dispersions ranging from volume fraction 10% to 30% were successfully fabricated by hot-pressing the Al2O3 nanocomposite powders with nano-sized BN coating, which was developed through a chemical process using boric acid and urea as BN source. The fracture strength is decreased to a small degree compared to the Al2O3 monolithic ceramics, while the fracture toughness is considerably improved. The composites with BN volume fractions over 20 % are found to be easily drilled using WC drill bits without lubrication. SEM observations reveal that the holes are cleanly drilled with no evident cracking or chipping. The surface roughness (RZ) of drilled section is （6 ± 0.5）μm. High mechanical properties and the ease of machining are attributed to the fine microstructure owing to inhibition of matrix Al2O3 grain growth by the finer h-BN dispersions and the cleavage of fine h-BN dispersions with laminar structure and large aspect ratio.
Key words: composites; alumina; boron nitride; mechanical properties; machinability
