(江蘇大學(xué) 材料科學(xué)與工程學(xué)院，鎮(zhèn)江 212013)
摘 要: 利用超聲化學(xué)熔體原位反應(yīng)技術(shù)合成顆粒增強(qiáng)(Al3Zr+ZrB2)/A356復(fù)合材料，通過SEM原位拉伸實(shí)驗(yàn)及其斷裂表面研究分析復(fù)合材料的斷裂行為。結(jié)果表明，復(fù)合材料的抗拉強(qiáng)度、屈服強(qiáng)度和伸長(zhǎng)率分別達(dá)到403.61 MPa、343.98 MPa和8.9%，較未施加超聲作用的復(fù)合材料分別提高16.09%、12.9%和32.83%；復(fù)合材料的室溫拉伸斷口SEM形貌表現(xiàn)出明顯的韌窩斷裂特征，為塑性斷裂。裂紋的萌生機(jī)制主要有基體在滑移過程中的位錯(cuò)作用機(jī)制、內(nèi)生Al3Zr和ZrB2顆粒脫落或破碎形成的空穴成核機(jī)制和基體缺陷誘發(fā)機(jī)制；由于內(nèi)生增強(qiáng)顆粒微觀分布上的不均勻性，當(dāng)主裂紋擴(kuò)展前方遇到顆粒密集區(qū)時(shí)，其擴(kuò)展方向偏向顆粒貧化區(qū)，繞過顆粒密集區(qū)，并沿顆粒富集區(qū)與貧化區(qū)的界面向前擴(kuò)展、延伸，形成宏觀裂紋。
關(guān)鍵字: 復(fù)合材料；超聲化學(xué)；原位拉伸；力學(xué)行為
（School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China）
Abstract:The particulates reinforcement (Al3Zr+ZrB2)/A356 composites were synthesized via ultrasonic chemistry melt in situ reactions, and the fracture behaviors were investigated by SEM in situ tensile observations and fracture surface characterizations. The results indicate that the tensile strength, yield strength and the elongation reach 403.61 MPa, 343.98 MPa and 8.9%, increase by 16.09%, 12.9% and 32.83% than those without ultrasonic assistance, respectively. The obvious dimple-crack characters on the SEM fracture surface of the composites were observed, and the fracture mechanism is plastic fracture. The crack initiation mechanisms are mainly the matrix dislocation actions mechanism during sliding, cavity formation mechanism due to the in situ Al3Zr and ZrB2 particle sloughing or bursting and the matrix defect induction mechanism. The crack growth is selective because of the non-uniform micro-distribution of the in situ particles. When the growing main cracks are faced to the particle-rich area, the growing direction is deflected to the particle-poor area, the cracks grow along the interface of the particle-rich area and the particle-poor area, and the macro-cracks are formed.
Key words: composites; ultrasonic chemistry; in situ tension; mechanical behavior
