【摘要】：Al-Si復(fù)合材料因其優(yōu)異物理和機(jī)械性能特點(diǎn)(受熱膨脹低、工件質(zhì)輕、比強(qiáng)度高和表面耐磨),在于航天結(jié)構(gòu)件應(yīng)用領(lǐng)域、電子類產(chǎn)品封裝領(lǐng)域、精密儀器加工行業(yè)廣泛使用,目前已成為材料界創(chuàng)新領(lǐng)域的一個(gè)重要投入點(diǎn)。該課題以顆粒增強(qiáng)材料強(qiáng)度理論作為實(shí)驗(yàn)研究基礎(chǔ),以Si顆粒和6061鋁合金粉末為原料,采用冷壓燒結(jié)法+熱擠壓、真空熱壓法制備了此復(fù)合材料。在材料測定相關(guān)技術(shù)(光學(xué)顯微鏡、SEM及XRD)下觀察了材料內(nèi)部微觀形態(tài)并測試鑒定了物相。通過測定復(fù)合材料的性能指標(biāo)(硬度、致密度、抗拉強(qiáng)度、膨脹系數(shù)等),根據(jù)實(shí)驗(yàn)數(shù)據(jù)系統(tǒng)研究了工藝參數(shù)(混粉方式、溫度,壓制力)在制備材料時(shí)對其微觀結(jié)構(gòu)和外在性能變化規(guī)律;嘗試了不同粉體處理方法及改變燒結(jié)過程對坯料施加的參數(shù)并對其影響進(jìn)行了深入研究,利用粉末冶金燒結(jié)原理分析了Al-Si復(fù)合材料的制備過程和機(jī)理,確定了材料制備工藝方法和詳細(xì)參數(shù)。試驗(yàn)表明:采用球磨混料方式既能顯著改善Al-Si混合粉末的幾何特性和燒結(jié)工藝特性,燒結(jié)后的材料組織和物理機(jī)械性能得到明顯提高。采用冷壓燒結(jié)法制備的Al-50Si復(fù)合材料的熱膨脹系數(shù)較低,達(dá)到9.8×10-6K-1;但其組織疏松(致密度為85.67%);其強(qiáng)度低和硬度差,坯料須受二次成型改善其組織。通過熱擠壓后,Al-50Si復(fù)合材料的物理機(jī)械性能明顯提高:材料的抗拉強(qiáng)度提高54%,致密度提高了14%,硬度提高了25%,但膨脹系數(shù)卻略微升高;同時(shí),復(fù)合材料內(nèi)部微觀組織得到明顯改善;增強(qiáng)體Si顆粒的偏聚明顯減弱,彌散均勻分布在鋁基體中;材料內(nèi)部的孔洞和缺陷明顯降低。采用真空熱壓法與經(jīng)過熱擠壓處理后的Al-50Si復(fù)合材料相比,材料的力學(xué)性能雖略低于熱擠壓的復(fù)合材料,但生產(chǎn)工序簡單并且避免了周期性魚鱗裂紋和尾縮的缺陷,材料的利用率得到了大大的提高。真空熱壓燒結(jié)過程中,隨著熱壓設(shè)備壓力從2×107Pa到6×107Pa過程中,材料的性能穩(wěn)步提升,當(dāng)壓力達(dá)到8×107Pa附近時(shí),樣品的物理、機(jī)械性能提升停止并呈下降趨勢。由于增強(qiáng)相硅顆粒脆性強(qiáng),壓力過大是導(dǎo)致其斷裂重要原因,伴隨裂紋產(chǎn)生抗拉性能不斷降低。硅顆粒含量從35%增加到50%時(shí),密度和抗拉強(qiáng)度逐漸下降,但其熱膨脹系數(shù)值從1.467×10-5K-1逐漸降到1.031×10-5K-1,材料的硬度值有所提高。最佳制備方法為混粉方式(球磨)+成型方式(真空下熱壓燒結(jié)),試驗(yàn)確定的工藝參數(shù)為:燒結(jié)溫度為565℃,燒結(jié)壓制壓力6×107Pa和保溫時(shí)間3.5h。
[Abstract]:Because of its excellent physical and mechanical properties (low thermal expansion, lightweight workpieces, high specific strength and surface wear resistance), Al-Si composites are located in the application field of aerospace structures, electronic product packaging, and so on. Precision instrument processing industry is widely used and has become an important input point in the field of material innovation. Based on the strength theory of particle reinforced materials and Si particles and 6061 aluminum alloy powder, the composites were prepared by hot extrusion by cold pressing and vacuum hot pressing. The microstructure and phase of the material were observed by optical microscope, SEM and XRD. By measuring the properties of the composites (hardness, density, tensile strength, expansion coefficient, etc.), the technological parameters (mixing method, temperature, etc.) were systematically studied according to the experimental data. (2) the change of microstructure and external properties of the material during the preparation of the material; The preparation process and mechanism of Al-Si composites were analyzed by means of powder metallurgy sintering principle, and the effects of different powder treatment methods and parameters on the sintering process were studied in detail. The preparation process and detailed parameters of the material were determined. The results show that the geometric and sintering characteristics of Al-Si powder can be improved by ball milling, and the microstructure and physical and mechanical properties of sintered powder can be improved obviously. The thermal expansion coefficient of Al-50Si composites prepared by cold pressing sintering is low, which reaches 9.8 脳 10 ~ (- 6) K ~ (- 1), but its microstructure is loose (density is 85.67%), its strength is low and hardness is poor, the structure of billet must be improved by secondary molding. After hot extrusion, the mechanical properties of Al-50Si composites were improved obviously: tensile strength increased 54%, density increased 14%, hardness increased 25%, but expansion coefficient increased slightly. At the same time, the microstructure of the composites was improved obviously, the segregation of Si particles was obviously weakened and dispersed uniformly in the aluminum matrix, and the pores and defects in the composites decreased obviously. Compared with the Al-50Si composites treated by hot extrusion, the mechanical properties of the composites by vacuum hot pressing are slightly lower than those of the hot extruded composites, but the production process is simple and the defects of periodic fish scale cracks and tail shrinkage are avoided. The utilization rate of materials has been greatly improved. In vacuum hot pressing sintering process, with the pressure of hot pressing equipment from 2 脳 107Pa to 6 脳 107Pa, the properties of the materials increase steadily. When the pressure reaches 8 脳 107Pa, the physical and mechanical properties of the samples stop and decrease. Because of the strong brittleness and excessive pressure of the reinforced silicon particles, the fracture is very important, and the tensile properties of the reinforced silicon particles decrease continuously along with the cracks. When the content of silicon particles increases from 35% to 50%, the density and tensile strength decrease gradually, but the thermal expansion coefficient decreases from 1.467 脳 10-5K-1 to 1.031 脳 10-5K / 1, and the hardness of the material increases. The best preparation method is powder mixing (ball milling) (hot pressing sintering under vacuum). The experimental parameters are as follows: sintering temperature is 565 鈩，

本文編號：2444568