【摘要】：Mg-8Sn系合金以耐腐蝕性優(yōu)異、強(qiáng)度高等優(yōu)點(diǎn)而逐漸成為鎂合金領(lǐng)域的研究熱點(diǎn)。目前大多數(shù)學(xué)者采用鑄造法制備Mg-8Sn系合金并進(jìn)行研究,而主要強(qiáng)化相Mg2Sn偏析嚴(yán)重、易粗化等問題導(dǎo)致鎂合金的塑性降低。針對(duì)此問題,本文提出了采用粉末冶金方法中的放電等離子燒結(jié)(SPS)法制備Mg-8Sn系合金,以期提高強(qiáng)化相Mg2Sn分布的均勻性且保證晶粒不粗化。按TAZ811配比對(duì)鎂粉末、錫粉末、鋅粉末和鋁粉末進(jìn)行高能球磨混粉,制得TAZ811合金粉末;采用SPS法制備不同燒結(jié)溫度(530℃、550℃、570℃、590℃)的鎂和鎂合金TAZ811。采用X射線衍射儀(XRD)和掃描電子顯微鏡(SEM)對(duì)其微觀組織和物相進(jìn)行觀察;探究SPS的燒結(jié)機(jī)理;利用萬能拉伸試驗(yàn)機(jī)對(duì)其宏觀力學(xué)性能進(jìn)行測(cè)試,并利用納米壓痕儀對(duì)其微區(qū)力學(xué)性能進(jìn)行研究;采用電化學(xué)腐蝕試驗(yàn)對(duì)其耐腐蝕性進(jìn)行測(cè)試。對(duì)比分析鎂和鎂合金TAZ811的界面行為并探討力學(xué)性能和耐腐蝕性差異的原因。高能球磨后的各組元粉末混合均勻,從而保證了析出相沿顆粒邊界分布均勻;SPS燒結(jié)過程升溫速度快、保溫時(shí)間短,顆粒尖端放電產(chǎn)生了局部高溫,可實(shí)現(xiàn)顆粒間的有效結(jié)合且晶粒不易長(zhǎng)大。不同燒結(jié)溫度的鎂和鎂合金TAZ811材料,組織結(jié)合較為良好,致密度可達(dá)98%以上。微觀組織觀察表明:鎂材料是由α-Mg相和顆粒界面處的MgO相組成;鎂合金TAZ811材料主要是由α-Mg相和顆粒界面處的析出相Mg2Sn相組成,Mg2Sn的厚度在1.4μm~3.6μm之間。宏觀力學(xué)性能表明:鎂材料的彎曲強(qiáng)度隨著燒結(jié)溫度的升高而增強(qiáng),當(dāng)燒結(jié)溫度為590℃時(shí),彎曲強(qiáng)度最高可達(dá)136 MPa;而TAZ811材料的彎曲強(qiáng)度隨著燒結(jié)溫度的升高先增加后降低,當(dāng)燒結(jié)溫度為570℃時(shí)彎曲強(qiáng)度最高,可達(dá)215 MPa。微觀力學(xué)性能表明:鎂材料的顆粒界面處和顆粒中央的硬度與彈性模量隨燒結(jié)溫度的升高而增大,界面處性能均比顆粒中央高,在590℃時(shí)顆粒界面處硬度最高,可達(dá)0.899 GPa,顆粒中央硬度最高達(dá)0.693 GPa;與之相應(yīng),模量最大值分別為39.538 GPa和36.879 GPa。TAZ811材料的顆粒界面析出相處和顆粒中央的硬度與模量隨著燒結(jié)溫度的升高而增大,到590℃時(shí)有所降低。在570℃時(shí)析出相附近的硬度最高,可達(dá)1.809 GPa,顆粒中央硬度最高達(dá)1.253 GPa;與之相應(yīng),模量最大值分別為59.433 GPa和48.249 GPa。電化學(xué)試驗(yàn)表明:鎂和鎂合金TAZ811材料的腐蝕形貌為顆粒邊界嚴(yán)重腐蝕,顆粒內(nèi)部有點(diǎn)蝕。隨著燒結(jié)溫度的升高,鎂材料的耐腐蝕性增強(qiáng),在590℃時(shí)耐腐蝕性最好,此時(shí)腐蝕電流為2.9632×10-5 A/cm2,腐蝕電位為-1.5593 V。隨著燒結(jié)溫度的升高,鎂合金TAZ811材料的耐腐蝕性先減弱后增強(qiáng),在590℃時(shí)耐腐蝕性最好,此時(shí)腐蝕電流為1.9632×10-5 A/cm2,腐蝕電位為-1.5218 V。
[Abstract]:Because of its excellent corrosion resistance and high strength, Mg-8Sn alloys have gradually become a hot spot in the field of magnesium alloys. At present, most scholars used casting method to prepare Mg-8Sn alloys and carried on the research, but the main strengthening phase Mg2Sn segregation is serious, easy to coarsening and so on, which leads to the decrease of the plasticity of magnesium alloys. In order to improve the uniformity of the Mg2Sn distribution of the strengthened phase and to ensure that the grain is not coarsened, the Mg-8Sn alloy was prepared by spark plasma sintering (SPS) in powder metallurgy. Magnesium and magnesium alloys TAZ811. with different sintering temperatures (530C, 550C, 570C, 590C) were prepared by high-energy ball milling of magnesium powder, tin powder, zinc powder and aluminum powder according to the ratio of TAZ811, and SPS method was used to prepare magnesium and magnesium alloy TAZ811. with different sintering temperature (530C, 550C, 570C, 590C). The microstructure and phase of SPS were observed by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The macro-mechanical properties were tested by universal tensile testing machine, and the micro-mechanical properties were studied by nano-indentation instrument, and the corrosion resistance was tested by electrochemical corrosion test. The interfacial behavior of magnesium and magnesium alloy TAZ811 was analyzed and the reasons for the difference of mechanical properties and corrosion resistance were discussed. The powder of each component after high energy ball milling is uniformly mixed so that the precipitated phase is uniformly distributed along the boundary of the particles. During the sintering process of SPS, the heating rate is fast, the holding time is short, the discharge at the tip of the particle produces local high temperature, and the effective bonding between the particles can be realized and the grain size is not easy to grow. The microstructure of magnesium and magnesium alloy TAZ811 with different sintering temperature is better and the densification is more than 98%. The microstructure observation shows that the magnesium material is composed of 偽-Mg phase and MgO phase at the grain interface, and the magnesium alloy TAZ811 material is mainly composed of 偽-Mg phase and precipitated phase Mg2Sn phase at the grain interface, and the thickness of Mg2Sn is between 1.4 渭 m ~ 3.6 渭 m. The macroscopic mechanical properties show that the bending strength of magnesium materials increases with the increase of sintering temperature. When the sintering temperature is 590C, the maximum bending strength can reach 136 MPa;. The bending strength of TAZ811 increases at first and then decreases with the increase of sintering temperature. When the sintering temperature is 570C, the bending strength is the highest, up to 215MPa.. The micromechanical properties show that the hardness and elastic modulus at the interface and the center of the particles increase with the increase of sintering temperature, and the properties at the interface are higher than those at the center of the particles. At 590C, the hardness at the interface is the highest (up to 0.899 GPa,). Particle center hardness up to 0.693 GPa; Accordingly, the maximum modulus is 39.538 GPa and 36.879 GPa.TAZ811, respectively, and the hardness and modulus in the center of the particles increase with the increase of sintering temperature, and decrease at 590 鈩，

本文編號(hào)：2444237