力學(xué)性能的影響
( 1. 中南大學(xué) 粉末冶金國家重點(diǎn)實驗室， 長沙 410083;
2. 西北有色金屬研究院， 西安 710016)
摘 要: 利用光學(xué)顯微鏡、 掃描電鏡(SEM)和透射電鏡(TEM)等手段研究了在粉末Ti合金中添加稀土元素對燒結(jié)坯的顯微組織和力學(xué)性能的影響。結(jié)果表明， 添加稀土元素可以有效提高燒結(jié)坯的致密度、 室溫抗拉強(qiáng)度和延伸率， 其中含1.0%Nd（質(zhì)量分?jǐn)?shù)）的材料致密度達(dá)99%， 抗拉強(qiáng)度1080MPa，延伸率6%， 接近鍛造Ti-6Al-4V合金的性能水平， 而且制備成本明顯降低。稀土元素對致密度的貢獻(xiàn)主要?dú)w因于在燒結(jié)過程中產(chǎn)生瞬時液相， 同時稀土元素能夠奪取粉末顆粒表面的氧， 凈化原始顆粒界面， 提高粉末顆粒的燒結(jié)活性。 致密度的提高， Ti合金基體氧含量的降低以及第二相Nd氧化物的存在都有助于材料力學(xué)性能的提高。 然而含Nd合金的燒結(jié)溫度應(yīng)控制在一個合適的范圍內(nèi)， 過高的燒結(jié)溫度將導(dǎo)致瞬時富Nd液相的聚集和元素的偏擴(kuò)散， 以及由于擴(kuò)散條件改善后的晶粒過度長大，反而不利于材料力學(xué)性能的提高。
關(guān)鍵字: 粉末冶金; Ti合金; 稀土; 力學(xué)性能
mechanical properties of powder metallurgy Ti alloy
（ 1. State Key Laboratory of Powder Metallurgy,
Central South University,Changsha 410083, China;
2. Northwestern Research Institute for Nonferrous Metals,
Xi′an 710016, China）
Abstract: The microstructure and mechanical properties of powder metallurgy(PM) Ti alloy doped with rare earth element Nd were investigated by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that addition of rare earth element can improve the density, tensile strength and elongation of PM Ti alloy. The alloy containing 1.0% Nd(mass fraction) has a relative density of 99%, tensile strength of 1080MPa and elongation of 6%. The above mechanical properties are almost the same as those of Ti-6Al-4V. The contribution of rare earth element to the density lies in that transient liquid phase occurs during sintering, and the rare earth element can scavenge oxygen from the powder surface, purify the particle interface and activate the sintering process. The increase of density, the decrease of the oxygen content of Ti substrate along with the existence of Nd oxides improve the mechanical properties of PM Ti alloy. However, the sintering temperature for Nd-containing alloy should be controlled properly. An excessively high sintering temperature can lead to agglomeration of Nd-rich liquids and coarsening of grains, hence deteriorates the mechanical properties of PM Ti alloy.
Key words: powder metallurgy; Ti alloy; rare earth element; mechanical property
