【摘要】：本文采用粉末冶金工藝制備了兩套低鏑高矯頑力燒結(jié)釹鐵硼磁體的工藝制度。開發(fā)出一套低鏑低成本燒結(jié)釹鐵硼磁體的制造工藝。采用本文的雙主相降鏑技術(shù)制備的雙主相磁體,比常規(guī)磁體矯頑力大幅增高,基于簡化的模型對雙主相磁體矯頑力的增強機制給出了定性解釋。采用本文的工藝制備磁體,實現(xiàn)了重稀土資源的高效利用。對燒結(jié)釹鐵硼磁體沖擊退磁進行了研究。全文主要結(jié)論如下：(1)成功研制出名義成分為Nd28.2DY2Fe68.8B的48SH,((BH) m=382kJ/m3, Hcj=1548 kA/m)低鏑高矯頑力燒結(jié)釹鐵硼磁體。合適厚度的富Nd相,可以使重稀土的得到優(yōu)質(zhì)化利用。(2)分析了磁體中晶粒異常長大的原因,并在此基礎(chǔ)上摸索出一套制備低鏑低成本燒結(jié)釹鐵硼磁體的工藝制度。通過制粉控制使磁體大部分的氧元素存在于晶界相中,這種工藝減少了原料浪費并縮短了生產(chǎn)時間,大大降低了磁體的生產(chǎn)成本。通過晶界的氧含量調(diào)控,改善高矯頑力磁體的燒結(jié)工藝制度。(3)通過研究,獲得了一種降鏑技術(shù)。制備的磁體被命名為雙主相磁體,它比常規(guī)的單合金法制備的磁體矯頑力大幅增高。首次制備并表征出雙主相磁體中含有兩種各向異性場不同的(Nd-Fe-B和Dy-Fe-B)晶粒結(jié)構(gòu)�？紤]了體積分數(shù)和晶粒尺寸對雙主相磁體矯頑力的影響, 給出半經(jīng)典公式：用形核場控制矯頑力機制對雙主相磁體矯頑力的增強效應給出了定性解釋。(4)制備了不同晶粒尺寸的雙主相磁體,磁體綜合磁性能最佳時,(BH)研究了磁體晶粒尺寸與晶界相的關(guān)聯(lián)效應,隨著磁體平均晶粒尺寸逐漸減小,主相晶粒尺寸分布集中,晶粒形貌變得規(guī)則。磁體角隅晶界處的富釹相尺寸較小,這就增加了條帶狀晶界相的數(shù)量,減少了角隅晶界相的比例,使磁體矯頑力提高。(5)開展了不同壓力的沖擊波對燒結(jié)釹鐵硼的加載實驗,沖擊波在磁體內(nèi)呈線性方式衰減。燒結(jié)釹鐵硼磁體退磁的臨界壓力不高于4.99 GPa。當沖擊波壓力在6.26≤P≤7.21 GPa之間時,磁體表面出現(xiàn)明顯的沿晶斷裂。隨著沖擊壓力的增加磁體取向度變差,磁體遭受沖擊后主相晶粒的取向發(fā)生偏轉(zhuǎn)。在900℃和520℃,先后回火2個小時后,磁體的矯頑力恢復,沿晶斷裂的現(xiàn)象消失。沖擊后磁體的晶界相晶體結(jié)構(gòu)沒有發(fā)生改變。磁體發(fā)生退磁的原因應該為：在磁體遭受沖擊瞬間,主相晶粒在高溫高壓的作用下擠壓富Nd晶界相,薄區(qū)富Nd相受到高溫擠壓向周圍移動導致主相晶粒相互連通；在沖擊后的磁體的晶界相中存在大量的微裂紋和孔洞,這些微裂紋和孔洞周圍形成低各向異性區(qū),成核場減弱；晶界相的滑移和斷裂改變了主相和晶界相的取向關(guān)系。提高磁體最大磁能積的同時降低磁體的抗沖擊性可增強功率源輸出功率。
[Abstract]:Two sets of NdFeB magnets with low dysprosium and high coercivity were prepared by powder metallurgy. A set of low dysprosium and low cost sintered NdFeB magnets was developed. The coercivity of the dual principal phase magnets prepared by the double principal phase drop dysprosium technique is much higher than that of the conventional magnets. Based on the simplified model, the mechanism of the coercivity enhancement of the dual principal phase magnets is explained qualitatively. The magnets were prepared by the technology in this paper, and the high efficiency utilization of heavy rare earth resources was realized. The impact demagnetization of sintered NdFeB magnets was studied. The main conclusions of this paper are as follows: (1) 48SHS, (BH) mN382kJ / m3, Hcj=1548 kA/m with nominal composition of Nd28.2DY2Fe68.8B have been successfully fabricated. The magnets sintered with low dysprosium and high coercivity have been successfully sintered into NdFeB magnets with low dysprosium and high coercivity. The rich Nd phase of suitable thickness can make the heavy rare earth get the excellent quality and utilization. (2) the reason of the abnormal grain growth in the magnet is analyzed, and on the basis of this, a set of process system for preparing low dysprosium and low cost sintered NdFeB magnets is found out. By means of pulverizing control, most of the oxygen elements of the magnets are present in the grain boundary phase. This process reduces the waste of raw materials, shortens the production time and greatly reduces the production cost of the magnets. The sintering process of high coercivity magnets was improved by controlling the oxygen content in grain boundaries. (3) A dysprosium reduction technique was obtained through research. The prepared magnets are named as two-phase magnets and the coercivity of the magnets prepared by single alloy method is much higher than that of conventional single-alloy magnets. Two kinds of anisotropic (Nd-Fe-B and Dy-Fe-B) grain structures have been prepared and characterized for the first time. The effects of volume fraction and grain size on the coercivity of the two-phase magnet are considered. The semiclassical formula is given: the enhancement effect of the coercivity of dual main phase magnets is explained qualitatively by means of nucleation field control coercivity mechanism. (4) two main phase magnets with different grain sizes are prepared, when the comprehensive magnetic properties of the magnets are optimal, The correlation effect between grain size and grain boundary phase is studied by (BH). With the decrease of average grain size of magnet, the distribution of main phase grain size is concentrated, and the grain morphology becomes regular. The size of the neodymium rich phase at the corner of the magnet is smaller, which increases the number of striped grain boundary phases and reduces the proportion of the corner grain boundary phases. The coercivity of magnets is improved. (5) the loading experiments of sintered NdFeB with shock wave at different pressures are carried out, and the shock wave attenuates linearly in the magnetic body. The critical pressure of sintered NdFeB magnets for demagnetization is no more than 4.99 GPa. When the shock wave pressure is 6.26 鈮，

本文編號：2327348