热处理对等离子喷涂铁基非晶合金涂层微观结构和耐腐蚀性能的影响

采用等离子喷涂技术在Q235钢基体上制备Fe48Cr15Mo14C15B6Y2非晶合金涂层,之后对涂层进行200,300,500,600,700℃热处理,研究了热处理对涂层微观结构、耐电化学腐蚀性能和耐均匀腐蚀性能的影响。结果表明:随着热处理温度的升高,涂层的非晶含量降低,孔隙率先减小后增大,经300℃热处理后涂层的孔隙率最低,且低于未热处理涂层的;热处理后涂层中的晶体相主要包括α-Fe,Fe-Cr,Fe63Mo37,Fe3C等;随着热处理温度的升高,涂层的自腐蚀电流密度先减小后增大,经300℃热处理后,自腐蚀电流密度最小,涂层的耐电化学腐蚀性能最好;经过热处理后,涂层在NaCl溶液中浸泡31d后的单位面积质量损失减小,且热处理温度越高,单位面积质量损失越小,涂层的耐均匀腐蚀性能提高。     

激光立体成形TC4钛合金的热力场演化

激光立体成形能够实现高性能复杂零件的精确成形，但成形过程中的高温度梯度极易导致残余应力和变形，最终影响构件的几何精度和力学性能。通过搭建基板单边夹持原位热变形测量系统，探究了多道多层TC4钛合金成形件在激光立体成形过程中基板温度、变形的演化规律，分析了不同扫描策略对构件热应力场的影响。研究结果表明，构件的变形发展受其热历史驱使，扫描策略对成形件的热变形具有显著影响。     

Al-Ga-Mn-Ca-Cu合金电极碱性体系电化学性能

通过熔铸、压延、退火等一系列工艺制作了新型Al-0.017Ga-0.885Mn-0.038Ca-0.048Cu (wt.%)阳极合金，并通过了EIS、极化曲线分析研究了其在不同浓度NaOH溶液中的腐蚀行为和电化学性能。结果表明，随着NaOH浓度的增加，合金阳极的自腐蚀速率在逐渐增加，Al-0.017Ga-0.885Mn-0.038Ca-0.048Cu合金在4mol/LNaOH溶液中的腐蚀速率增长速度明显降低，放电电压在电流密度为120mA/cm2下仍能维持在1 V左右，阳极能量密度也最高，达6.056kW?h/kg，更适合不同电流密度下的连续恒流放电。且合金的恒流放电和EIS结果与腐蚀特性吻合较好。     

Synthesis and characterization of hydrogenated novel AlCrFeMnNiW high entropy alloy

A novel high entropy alloy (HEA) i.e. AlCrFeMnNiW is synthesized via high-energy planetary ball milling with an average crystallite size of 10.37 nm. The morphology study of hydrogenated and dehydrogenated HEA is carried out through Scanning Electron Microscope (SEM). The HEA is charged with hydrogen using inhouse Sievert's Apparatus which results to be maximum hydrogen storage capacity of 0.615 wt% at atmospheric pressure and temperature. The dehydrogenation of the sample is performed through thermogravimetry (TG) at different scanning rate. The crystalline structure (i.e. lattice parameters) and chemical composition of HEA is studied using X-Ray Diffraction (XRD) and Energy Dispersive X-Ray analysis (EDX) respectively. The unit cell volume of as-prepared alloy is estimated as 0.03131 nm³ whereas the average crystallite size as 10.37 nm. It is observed that the unit cell volume is increased by 0.67% and crystallite size decreased by 10.8% upon hydrogenation whereas it is then decreased by 0.2% and increased by 6.7% respectively upon dehydrogenation. Activation energy during hydrogen desorption is found to be −8.161 kJ/mol. The enthalpy and entropy of the mixing are estimated to be −2.645 kJ/mol and 1.793 R J/mol K.     

轧制与退火对T9S钛合金板材组织与性能的影响

研究了轧制变形量及退火温度对T9S钛合金板材显微组织和室温力学性能的影响。结果表明:增加成品轧制变形量,板材组织破碎更充分,退火后形成等轴α相、拉长α相和晶间β相组织形貌,变形流线比较明显,板材室温强度和硬度升高,伸长率降低,弹性模量增加。随着退火温度升高,板材室温强度和硬度逐渐降低,伸长率逐渐提高,横向弹性模量逐渐减小,纵向弹性模量先增加后减小。经(750~790) ℃×45 min空冷退火处理后的板材可以获得较好的强度和塑性的匹配。     

铝空气电池用6061和7075铝合金阳极电化学性能

研究了工业6061铝合金（6061）、航空7075铝合金（7075）和纯铝作为铝空气电池阳极材料的电化学性能，分析其作为阳极的可行性及适用环境。进行了阻抗、极化曲线和恒电流放电实验并进行了表面表征，计算了在40～120mA/cm²电流密度下连续恒流放电的阳极能量密度。用电子探针显微镜（EPMA）对电极表面形貌进行了研究，用波谱分析仪（WDS）进行表面分析。研究结果表明，合金元素在电池放电过程中会改变阳极的表面特性。6061中合金元素含量对电池阳极材料的性能产生了积极影响，使得合金的表面放电面积变大，放电均匀，更适合作为铝空气电池阳极材料。     

磨削表面粗糙度对γ-TiAl合金抗弯强度的影响

为了研究表面加工质量对硬脆性高温合金抗弯性能的影响,对不同磨削表面粗糙度的全片层γ-TiAl(Ti-47.5Al-2.5V-1.0Cr)合金进行了抗弯性能试验,分析了表面粗糙度对其抗弯强度的影响规律。试验结果表明,随着表面粗糙度的增大,全片层γ-TiAl合金的抗弯强度明显降低。结合断裂形貌图分析了全片层γ-TiAl合金组织中裂纹的萌生、扩展及最终发生宏观断裂的方式,全片层γ-TiAl合金裂纹大多起裂于因加工纹理引起的应力集中区域附近的片层间,并优先在层间扩展,最终的断裂形式多为穿层的脆性瞬断。     

Effect of thermomechanical processing on microstructure and mechanical properties of CoCrFeNiMn high entropy alloy

The CoCrFeNiMn high entropy alloy was produced by homogenization, cold rolling and recrystallization. The effects of thermomechanical processing on microstructures and tensile properties at different temperatures were investigated using X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and multi-functional testing machine. The results show that dendritic structures in cast alloy evolve into equiaxed grains after being recrystallized, with single face-centered cubic (FCC) phase detected. The most refined alloys, stemming from the highest rolling ratio (40%), exhibit the highest strength due to the grain boundary strengthening, while the variation of elongation with temperature shows a concave feature. For the coarse-grained alloys, both the ductility and work hardening ability decrease monotonically with increasing temperature. Serrated flow observed at intermediate temperatures is attributed to the effective pinning of dislocations, which manifests the occurrence of dynamic strain hardening and results in the deterioration in ductility. Besides, dimples on the fracture surfaces indicate the typical ductile rupture mode.     

Effect of different quenching processes following solid-solution treatment on properties and precipitation behaviors of 7050 alloy

The effects of quenching in different ways following solid-solution treatment on properties and precipitation behaviors of 7050 alloy were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED), hardness and electrical conductivity tests. Results show that after quenching in different ways, electrical conductivity of the alloy decreases rapidly in the first 48 h of natural aging. The electrical conductivity of 7050 alloy in natural aging state is determined by the size and density of GP zones, and the size of GP zones is the main factor. After natural aging for 70 d, the size of GP zones is 1.8–2.6 nm in matrix of the immersion quenched sample and it is 1.4–1.8 nm in matrix of both water mist and forced air quenched samples. After natural and artificial peak aging, the hardness of the water mist quenched sample is HV 193.6 and its electrical conductivity is 30.5% (IACS) which are both higher than those of the immersion quenched sample. Therefore, water mist quenching is an ideal quenching method for 7050 alloy sheets after solid-solution treatment.     

Solidification of Be-free Ni-based dental alloy

A novel, Nb- and Si-rich and Be-free Ni-based alloy was cast by two methods of investment casting and continuous casting to study the microstructure evolution during solidification and its mechanical properties. The solidification of the alloy started with the primary crystallization of FCC-γ, followed by a binary eutectic reaction, with the formation of a heterogeneous constituent: FCC-γ+G-phase, which replaced the low-melting eutectic (FCC-γ+NiBe) in the Be-bearing alloys. AlNi₆Si₃ and γ′ formed during the terminal stages of solidification by investment casting, while the formation of AlNi₆Si₃ was suppressed by continuous casting. The Scheil solidification model agreed very well with the experimental results.