强变形诱导析出相回归后的再时效行为

利用透射电镜和硬度测量实验手段,研究了强变形诱导析出相回归后的合金在再时效过程中的组织、性能变化.发现:多相合金Al-Zn-Mg-Cu经固溶、时效处理后,析出相粒子在强变形过程中破碎细化并可重新回归于基体内.强变形导致回归后的合金在再时效处理时可再次沉淀析出第二相粒子,但析出相的析出顺序与强变形后合金的晶粒尺有相关,当晶粒细化到某一临界尺寸以下时,析出顺序发生改变,非均匀形核的平衡相可抑制GP区、η亚稳相等前期粒子的析出.     

二次热等静压对TC4合金组织的影响

研究了二次热等静压(HIP)工艺对不同起始组织HIP态TC4合金显微组织的影响.结果表明,二次HIP主要通过扩散进行组织的致密化,致密化过程中形成等轴块状α相填充孔洞,同时原始致密组织中片状α相层片间距增大.与首次HIP相比,二次HIP的致密化过程相对较慢,孔隙尺寸较大体积分数高的初始组织,经二次HIP后会形成不均匀组织,为了获得细小均匀的致密组织,应尽量在首次HIP时完成致密化.     

Evolution of undissolved phases in high-zinc content super-high strength aluminum alloy during ageing

The evolution of undissolved phases in the high-zinc content super-high strength aluminum alloy during ageing was investigated by means of SEM and EDS. The results show that undissolved phases of Cu-rich M(AlZnMgCu) exist in the silver-free alloy at solid-solution state. With increasing the ageing time, the precipitation of agehardening precipitates MgZn2 stimulates Zn atoms within the undissolved phases to diffuse into the matrix, and thus the Cu content in the M(AlZnMgCu) phase increases relatively. For the silver-bearing alloy, small addition of Ag promotes the formation of Ag-rich M(AlZnMgCuAg) undissolved phases and deteriorates mechanical properties of the alloy. At the early stage of ageing, Ag content within the M(AlZnMgCuAg) phases greatly decreases due to rapid diffusing of Ag atoms into the matrix and the co-clustering of Ag and Mg atoms. As the ageing time prolonging, the precipitation of MgZn2 results in the decrease of Zn content in the undissolved phases, and the relative increase of Ag and Mg contents.     

稀土元素镱在ZK31镁合金中的分布

研究了ZK31 xYb合金中Yb的分布及作用.结果表明:Zn和Yb能相互降低对方在镁合金中的溶解度,少量(1.0%)的Yb加入ZK31合金中,Zn与Yb的分布都较均匀,在凝固过程中优先形成Yb-Zn金属间化合物,提高Yb含量(2.0%),Yb向晶界偏聚,并促使Zn向晶界偏聚,凝固过程中有少量金属间化合物Mg2Zn2Yb先于α-Mg形成,大部分的Yb和Zn在凝固后期形成金属间化合物Mg15Zn2Yb,进一步提高Yb的含量,固溶以外的Yb和Zn均向晶界偏聚,在凝固后期形成金属间化合物Mg15Zn2Yb和Mg10Zn3Yb2.此外,Yb元素能有效细化ZK31镁合金的晶粒.     

钛合金HIP近净成形技术在航天上的应用

介绍了钛合金热等静压(HIP)近净成形的工艺特点及其在国内外航天领域的应用情况.与锻造、精密铸造、机械加工等传统成形方法相比,HIP近净成形钛合金综合力学性能高,节约原材料、成形周期短.由于产品的综合力学性能高、尺寸精度可控性好,HIP近净成形技术非常适合异型结构件特别是含空间曲面结构件的精密成形.     

镱对挤压ZK31镁合金室温力学性能的影响

研究了Yb对挤压ZK31镁合金的组织与力学性能的影响。结果表明:添加1.0wt%Yb能显著提高ZK31镁合金的综合力学性能,提高合金强度的主要原因是抑制挤压过程中的动态再结晶(DRX),细化ZK31镁合金加工态晶粒(<5μm),给随后的热处理带来有利的影响。ZK31+1.0Yb合金挤压后直接进行423K×24h时效处理与挤压态相比,可同时提高强度和塑性,获得最佳力学性能:σb=313MPa,σ0.2=293MPa,δ=19.1%。     

Twinning during hot compression of ZK30 ＋ 0.3Yb magnesium alloy

The twinning process of ZK30＋0.3Yb magnesium alloy was studied. The results show that twinning occurs at the initial stage of deformation, and decreases during further deformation. The original grain is fragmented after small straining. It is investigated that the twinning boundary activates the occurrence of the non-basal slip system due to the stress concentration at the vicinity of twin boundary introduced by the dislocation pile-ups at the vicinity of twinning boundary. The rearrangement of dislocation after dislocation climb introduces new grain boundary. Simultaneously, twinning occurs to form “polygonization” due to the stress concentration relaxation, and the “polygonization” will transform into low angle boundary to refine the original grain under the shear stress with further straining.     

镁基轻质合金的发展

综述了镁合金系的发展变化,各种微量添加元素对镁合金的作用;镁合金变形加工的特点,及镁合金热处理时效析出的特点,总结了现有的二元镁合金时效沉淀过程,析出相的结构及其与基体的位向关系.     

一种新型超高强铝合金的力学性能研究

通过差热分析、金相组织观察、常温拉伸实验及SEM形貌观察等手段,分析了不同固溶工艺对高Zn的A1-10．4％Zn-2．2％Cu-2．4％Mg-(0．10～0．15)％Zr-0．224％Ag合金的微观组织和力学性能的影响。结果表明,采用接近低熔点共晶熔化温度的强化固溶工艺及单级时效处理后,合金的力学性能明显优于单级固溶和低温强化固溶工艺,其抗拉强度达到770MPa以上,而对应的延伸率保持在8％～10％。与国内开发的其他7000系合金相比,该合金显示出超高强度和良好的塑性,这说明合理的固溶工艺可使高合金化的超高强铝合金的强度和塑性达到良好的配合。但是,SEM观察表明,在合金固溶组织中仍残留部分粗大第二相粒子,这必然对合金的综合性能造成不利影响,因此固溶工艺还有待进一步优化。