共查询到16条相似文献,搜索用时 402 毫秒
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喷射成形Mg-9Al-xZn合金的微观组织演变 总被引:1,自引:0,他引:1
利用喷射成形技术制备AZ91、AZ92和AZ93镁合金沉积柱坯,并对其微观组织演变进行观察.结果表明:铸态普通凝固AZ91合金的晶粒粗大,脆性β-Mg17Al12相连续分布成网状结构;而喷射成形AZ91、AZ92和AZ93合金的组织均匀,晶粒被充分细化,β-Mg17Al12相的网状结构被打破;喷射沉积快速凝固条件下高的冷却速率促进了过饱和α-Mg固溶体组织的形成,使得偏析相减少,形态改善;Zn含量的增加降低了Al在Mg中的溶解极限,促进了β-Mg17Al12相在晶界的析出及α-Mg+β-Mg17Al12离异共晶组织的形成;Zn元素的偏析倾向为激活成分过冷区内的形核质点提供了驱动力,从而阻碍了晶粒长大. 相似文献
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典型β型钛合金元素Cu,Fe和Cr的偏析规律 总被引:1,自引:0,他引:1
通过对Ti-2.5Cu,Ti-3Fe,Ti-3Cr,Ti-13Cu-1Al,Ti-6Al-1.7Fe几种合金铸锭成分的对比研究,建立了典型β钛合金元素的偏析模式。对Ti-2.5Cu,Ti-3Fe,Ti-3Cr合金铸锭的对比可知,Cu和Fe元素的偏析程度大,Cr元素的偏析程度小;对Ti-2.5Cu和Ti-13Cu-1Al合金铸锭的对比可知,Cu元素在2种合金铸锭中的偏析均比较明显,Cu含量越高,偏析程度越大;Cu元素在2种合金铸锭的晶界有截然不同的偏析方式,Cu元素在Ti-13Cu-1Al的晶界富集而在Ti-2.5Cu的晶界贫化。对Ti-3Fe和Ti-6Al-1.7Fe合金铸锭的对比可知,Fe元素在2种合金铸锭中的偏析均比较明显,Fe含量越高,偏析程度越严重;Fe元素在2种合金铸锭的晶界均贫化。 相似文献
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本文论述了影响热处理钢轨性能的组织参数--奥氏体晶粒尺寸,珠光体片间距、渗碳体片厚度等。指出奥氏体晶粒尺寸主要受加热温度(考虑到电感应加热速度快,保温停留时间短)的控制,而珠江体片间距和渗碳体片厚度主要取说不过去这冷奥氏体的转变温度和冷却速度,当然受合金元素的加入及其含量影响。同时指出,珠光体钢的强度主要受珠光体的片间距的控制,而钢的韧性则主要取决于奥氏体晶粒尺寸的大小。珠光体片间距越细则强度越高 相似文献
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研究了Al含量、冷却速率和添加硼元素对TiAl合金全片层组织在1150℃的热稳定性的影响。研究表明:Al含量在46%~48%(原子分数,下同)范围的二元TiAl合金的Al含量越高,γ偏析程度越严重,铸造片层组织的热稳定性越差;Ti-48AI合金α单相区固溶处理后炉冷的粗片层组织的稳定性远远优于空冷的细片层组织,空冷细片层组织容易在晶界处发生不连续粗化转变,并且空冷片层晶粒内的魏氏片层(LW)与基体的界面往往与晶界一同成为片层组织发生分解的起始部位;Ti-48A1合金中添加0.8%B因晶界TiB2相的存在能有效抑制细片层组织的晶界不连续粗化,但γ相从TiB2/基体界面和晶界重新形核生长可使片层组织转变为均匀的细晶近γ组织。 相似文献
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In order to reduce the segregation of alloying elements during casting of 100Cr6 high carbon chromium bearing steel, cerium was added to form dispersoids that act as inoculants to facilitate the formation not of columnar but of equiaxed grains. The influence of adding cerium alone to 100Cr6 steel on the degree of segregation and the resulting as-cast microstructure have been investigated. By adding cerium, the equiaxed grains became finer and the segregation diminished considerably. As a result, the rolling contact fatigue life of the steel was improved markedly. Among dispersoids, CeO2 is supposed to play a more important role in refining as-cast structures because the observed number of CeO2 was much larger than that of CeS and the size of the former was quite similar to that reported to be effective as inoculants. Consequently, the addition of cerium is proposed as the solution to one of the biggest subjects with regard to 100Cr6 steel, the reduction of segregation during casting. 相似文献
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利用旋转磁场控制Mg15Al二元高铝镁合金凝固过程,以期获得均匀细小的等轴晶,使合金后续的等通道挤压能顺利进行.通过OM、SEM、EDS测试手段研究了旋转磁场对合金凝固组织及溶质分配的影响.结果表明:旋转磁场主要通过与金属液流相互作用引起强烈的旋流而产生搅拌作用来影响合金的温度场与溶质场的分布,故能够显著细化Mg15Al二元高铝镁合金组织中的初晶a-Mg,促进Al在初晶a-Mg中的固溶,但对于在凝固末期才形成的共晶组织而言,由于凝固末期所剩液相形不成有效流动,其形态受旋转磁场影响不大.随励磁电压增大,晶粒细化效果增加,励磁电压为60 V时,晶粒细化效果最佳,A1在初晶a-Mg中固溶量最高,励磁电压继续增加,由于磁场感生热增加将弱化二次冷却,使晶粒细化效果下降. 相似文献
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研究了二冷汽雾冷却和全水冷却条件下拉速、比水量和结晶器电磁搅拌对SWRH82B碳偏析指数的影响。结果表明:二冷汽雾冷却条件下,比水量为1.16和1.25 L/kg时,拉速1.7 m/min与末端电磁搅拌位置最匹配,且随比水量由0.94增大到1.25 L/kg,碳偏析指数由1.17降低到1.10,提高结晶器电磁搅拌电流由250 A到350 A,碳偏析指数改善不明显;对二冷由汽雾冷却向全水冷却实施改造,得出比水量为1.6 L/kg,拉速为1.7 m/min,结晶器电磁搅拌350 A/3Hz为最佳参数,铸坯中心碳偏析平均指数达到最小值1.05。 相似文献
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Zijian Yu Xi Xu Baotian Du Kang Shi Ke Liu Shubo Li Xiuzhu Han Tao Xiao Wenbo Du 《金属学报(英文版)》2022,35(4):596
In this study, the Mg-4Y-1Gd-1Nd-xCa-1Zn-0.3Zr (x = 0 and 0.4 wt%) cast alloys with low rare earth concentration were prepared in different routes of heat treatments, and their microstructures and mechanical properties were investigated. The Mg-4Y-1Gd-1Nd-1Zn-0.4Ca-0.3Zr cast alloy with ultimate tensile strength (UTS) of 264 ± 7.8 MPa, tensile yield strength (TYS) of 153 ± 1.2 MPa and elongation to failure (EL) of 17.2 ± 1.2% was successfully developed by appropriate heat treatment. The improved mechanical performance was attributed to the combined strengthening effects of fine grains, Mg24RE5, $\beta ^{\prime}$, $\beta _{1}$, $\gamma ^{\prime}$ and LPSO phases. In the heat treatment process, cooling method of T4 treatment affected the microstructure, which consequently determined the mechanical properties air cooling, rather than water cooling, gave rise to the formation of $\gamma ^{\prime}$ phase in the alloy without Ca addition. However, Ca addition facilitated the formation of $\gamma ^{\prime}$ phase, and the $\gamma ^{\prime}$ phase precipitated in the alloy after T4 treatment either by water cooling or by air cooling, but the air cooling increased the number density of $\gamma ^{\prime}$ phase in comparison to the water cooling. Although the $\gamma ^{\prime}$ phase strengthened the studied alloys, the formation of $\gamma ^{\prime}$ phase inhibited the precipitatition of $\beta ^{\prime}$ and $\beta _{1}$ phases in the following T6 treatment, and consequently reduced the strengthening effect of $\beta ^{\prime}$ and $\beta _{1}$ phases. The results showed that the mechanical performance of the studied alloys was largely determined by the precipitation of $\gamma ^{\prime}$ phase, which was regulated by the Ca addition and the cooling method of T4 treatment. 相似文献