铸锭枝晶间距和冷变形量对Cu-15Ni-8Sn合金显微组织和硬度的影响

采用中频感应炉与高频感应炉制备了枝晶间距分别为11,18,23,50μm的Cu-15Ni-8Sn合金铸锭,并依次进行了均匀化退火处理、固溶处理、冷变形和时效处理,研究了铸锭枝晶间距和冷变形量对合金显微组织和硬度的影响。结果表明:试验合金铸锭的显微组织均为明显的树枝状组织;经均匀化退火及固溶处理后,铸锭枝晶间距越小的合金组织也越趋于均匀;冷变形量越大,合金中的晶粒变形越严重,且经400℃时效后合金中的黑色不连续脱溶产物越早析出,时效硬度峰也越早出现;在相同的冷变形量下,铸锭枝晶间距越小的合金中黑色不连续脱溶产物越晚析出,且时效硬度峰越晚出现。     

冷拉拔过程中含稀土铝镁合金的组织与力学性能演变

熔炼制备不同稀土加入量的Al-3.0Mg-xRE(质量分数/％,x=0,0.12,0.31,RE为La+Ce)合金,研究了该合金的显微组织、硬度和拉伸性能在冷拉拔过程中的演变规律.结果表明:冷拉拔过程中,试验合金的晶粒拉长,第二相拉长并破碎成细小粒子,并在晶界和枝晶界处逐渐聚集呈线状分布,Copper{112}<111>型变形织构强度逐渐增高;随着变形量的增大,合金的强度呈线性增大,塑性降低,显微硬度增大;适量稀土(0.12％)的加入能够改善合金组织与力学性能,但过量稀土(0.31％)的加入会导致合金中第二相数量和尺寸的增加,从而降低合金的力学性能.冷拉拔后,Al-3.0Mg-0.12RE合金中第二相的长度最小,数量最少,变形织构强度最高,力学性能最优.     

含钪Al-Zn-Mg-Zr合金双级时效工艺的正交优化

采用正交试验对含0.25%(质量分数)钪Al-Zn-Mg-Zr合金的双级时效进行了工艺优化,研究了双级时效工艺参数(预时效温度和时间、终时效温度和时间)对合金力学性能和电导率的影响,观察了最佳工艺处理后合金的显微组织。结果表明:对该合金综合性能,尤其是力学性能影响程度由大到小的参数依次为终时效温度、终时效时间、预时效时间、预时效温度;该合金适宜的双级时效工艺为120℃×4h+140℃×12h,经该工艺处理后,合金的抗拉强度为553 MPa,屈服强度为534 MPa,伸长率为12.0%,电导率为37.3%IACS;合金基体组织中弥散分布着η′相以及Al3(Sc,Zr)粒子,有助于合金强度以及抗应力腐蚀性能的提高。     

在高压扭转大塑性变形及时效过程中6201铝合金组织和硬度的变化规律

在室温下对挤压态6201铝合金进行不同转数(1,2,5,10,20 r)的高压扭转变形以及175℃保温不同时间(10,60 min)的时效处理,研究了变形及时效过程中组织和硬度的变化规律。结果表明：随着高压扭转转数的增加,晶粒尺寸由微米级细化至亚微米级,晶粒趋向于变为等轴晶,合金硬度升高;当高压扭转转数大于10 r后,合金组织稳定,晶粒尺寸约为183 nm,硬度基本保持不变。随着时效时间的延长,高压扭转10 r合金的晶粒逐渐长大和粗化,时效60 min后,次中心位置平均晶粒尺寸约为523 nm;合金发生明显的时效软化,随着时效时间的延长,合金硬度降低。     

一种新型铝合金力学性能研究

采用硬度测试、室温拉伸、电导率测试等技术研究了Al-Mg-Si-Cu合金的室温力学性能及电导率。结果表明:Al-Mg-Si-Cu合金有明显的欠时效、峰值时效、过时效三个阶段的时效硬化特性,其峰值时效硬度最大为143.4 HV,在峰值时效后在较短时间内硬度下降更快;Al-Mg-Si-Cu合金适宜的固溶制度为550℃/2h,峰值时效制度为155℃/14h;在时效温度范围一定的条件下,时效温度越低,峰值时效条件下的合金强度越高;随着时效温度的升高或时效时间的延长,电导率呈小幅升高趋势;相比于时效时间,电导率的变化随时效温度的变化更为明显。     

压缩与半固态等温热处理对Mg-3Al-0.8Gd合金组织与性能的影响

对Mg-3Al-0.8Gd合金进行了压缩变形及半固态等温热处理,研究了压缩变形量(10%,15%,20%)、等温温度(530,540,550,560,570℃)及保温时间(3,5,10,15min)对该合金显微组织与硬度的影响,并对比了铸态和热处理态Mg-3Al-0.8Gd合金的拉伸和冲击性能。结果表明:不同条件压缩变形及等温热处理后,Mg-3Al-0.8Gd合金组织均由α-Mg基体和β-Mg_(17)Al_(12)相组成;随着等温温度、保温时间及压缩变形量的增加,合金中的α枝晶逐渐转变为等轴晶,晶粒细化,组织均匀性提高,同时显微硬度增大;压缩变形20%并经550℃保温15 min热处理后,Mg-3Al-0.8Gd合金的抗拉强度、断后伸长率、断面收缩率和冲击吸收能量较其铸态合金的分别提高了11.3%,32.6%,3.8%和23.3%。     

添加锆对Al-Mg-Si合金时效组织和性能的影响

研究了加入质量分数0．15%锆对Al-Mg-Si合金时效(170℃×8h)后及在随后保温(250℃)过程中力学性能和组织的影响。结果表明：加入锆后,合金时效硬度值和力学性能均有一定程度的提高;随保温时间的延长,含锆合金硬度比未含锆合金硬度高,且降低趋势缓慢;主要原因是加入锆后形成了Al_3Zr弥散相粒子,强化了Al-Mg-Si合金。     

铜银锆合金热处理工艺的优化及析出相

对经不同热处理后铜银锆合金的性能进行了研究,通过透射电镜分析了合金中析出相的种类及形貌。结果表明:合金经920℃×40min固溶水淬+30%冷变形+420℃×3h时效空冷处理后,能获得较好的力学性能与电学性能,硬度为123HB,电导率为88.8%IACS,室温抗拉强度为430MPa,断后伸长率为13.5%,断面收缩率为45.2%;热处理后合金基体上弥散分布着Cu5Zr析出相和粗大的铜银锆饱和固溶体。     

新型铝锌镁铜系高强韧铝合金型材的双级时效工艺

通过时效处理和拉伸性能测试等方法得到了适用于一种新型铝锌镁铜系高强韧铝合金挤压型材的双级时效工艺。结果表明:在双级时效处理后该合金的析出相主要为η′相和少量的η相,随着二级时效时间的延长,η相数量增加,沉淀相尺寸增大;试验合金的硬度随着时效时间的延长先增大后减小,强度随二级时效时间的延长而下降,伸长率则增大;得到合适的时效工艺为120℃×4h+165℃×6h,经该时效工艺处理后试验合金的抗拉强度为566 MPa,屈服强度为540 MPa,伸长率为10.9%,电导率为40.8%IACS,优于T74态7050铝合金的。     

铜镍钴铍合金的时效相变动力学方程

研究了铜镍钴铍合金固溶后时效处理工艺对其电导率的影响,通过电导率与析出的第二相体积分数的关系推导了该合金的相变动力学方程.结果表明:该合金固溶后在不同温度时效时随着时间的延长,电导率开始增加较快,经3～4 h时效后增速减慢;时效温度越高,时效初期电导率的上升速率越大,最终电导率也越高;时效过程中电导率的增加量与第二相的...     

稀土钇对Zn-25Al铸态组织及力学性能的影响

以Zn-25Al合金为基体材料,通过常规铸造方法制备了不同稀土含量的锌铝合金。采用金相显微镜、扫描电镜、拉伸试验机、硬度计等分析研究了稀土Y对试验合金显微组织和力学性能的影响。试验结果表明,添加稀土钇后,在锌铝合金中,其与Al、Zn等元素形成硬度高、热硬性好的复杂成分化合物且分散于晶界和枝晶中,细化了组织,有效地阻碍了高温时基体的变形和晶界移动。随着钇含量的增加,在室温、100℃和180℃3个温度下合金的抗拉强度和硬度基本上呈先升后降的趋势。当钇含量为0.6%时合金的综合性能最好,高温强度和硬度提高显著。180℃时的抗拉强度比不加Y时提高33.3%,硬度提高64.9%。当钇含量超过0.6%时力学性能下降。     

热处理对铜铍钴钛合金组织和性能的影响

对新型铜铍钴钛合金进行了固溶时效热处理,研究了热处理工艺对其组织和性能的影响。结果表明:该合金经840℃×50min固溶+300℃×2h时效处理后,其硬度为38HRC,电导率为21.89%IACS,晶界和晶内有细小弥散的γ相析出;时效处理可以使该合金的电导率得到显著提高。     

热处理对挤压添加钙AM50镁合金组织及力学性能的影响

研究了固溶、时效对挤压添加钙的三种AM50镁合金组织和力学性能的影响。结果表明：合金挤压后,随着固溶时间的增加,Mg17,Al12相以弥散状溶解在基体镁中,而Al2Ca相相当稳定,部分变细,逐步断开并出现球化现象;随着时效时间的增加,Mg177Al12相以粒状从基体中析出,而Al2Ca相在时效过程中变化极小。固溶后,挤压合金的硬度和抗拉强度下降。时效后,挤压添加1％Ca的合金抗拉强度略有升高,未加和加入2％Ca的抗拉强度略有下降,三种合金的硬度增加到峰值后逐步下降。未加和加入29,6Ca的合金固溶后塑性显著增加,时效后塑性略有下降;而加入1％Ca的合金固溶后塑性略有下降,时效后塑性显著提高。     

Wear of two-phase metals

The effect of the second-phase particle structure on the wear properties of two-phase metals was investigated by using precipitation-hardened copperchromium alloys (Cu-0.58 at.% Cr and Cu-0.81 at.% Cr) aged for different periods of time at 500 °C. The hardness of these materials was found to increase initially with the aging time and then to decrease; the maximum value was reached after about 100 min of aging. Metallographic examination of worn specimens indicated that the wear process proceeded by subsurface deformation, crack nucleation and crack propagation, i.e. by delamination. The friction coefficient was found to be constant for both alloys and for all aging times. In the early stages of precipitation both the wear rate and the wear coefficient decreased. As the aging continued the wear rate and the wear coefficient increased even though the hardness also increased. The wear coefficient remained constant for the overaged alloys. The decrease in both the wear rate and wear coefficient in the early stages of precipitation is due to the fact that particles are small and coherent and require a large amount of subsurface deformation for crack nucleation. With further aging, the particles grow and become incoherent, increasing the wear rate due to easier crack nucleation. For the case of the overaged alloys, the wear coefficient tends to become constant because the wear process is controlled by the crack propagation rate which is found to be independent of the aging time for both alloys.     

粉末冶金铝-铁合金的组织和性能

以铝粉和铁粉为原料,采用冷压烧结方法制备出铝-铁合金,并进行热挤压加工,研究了它的纽织和性能.结果表明：随着铁含量增加,抗拉强度先升后降,伸长率下降,硬度和耐磨性增高;Al、Al-10Fe和Al-20Fe合金的磨损体积损失分别是QSn6.5-0.4的1/0.66,1/12.2和1/20.1,磨损表面呈铝基体、Al13Fe4硬质相和少量孔隙的耐磨组织.     

Effect of Micro-scale Y Addition on the Fracture Properties of Al–Cu–Mn Alloy

Rare earth (RE) elements have positive effects on Al alloy, while most research is focused on microstructure and mechanical properties. As important application indices, toughness and plasticity are properties that are sensitive to alloy fracture characteristics, and few research studies have characterized the fracture properties of Al–Cu–Mn alloy on RE elements. The effect of different contents of Y on the fracture properties of Al–Cu–Mn alloy is investigated. T6 heat treatment (solid solution and artificial aging treatment), optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) methods are applied to the alloy. Results showed that when Y element is present at 0.1%, the section of the as-cast alloy has smaller sized dimples and the fracture mode presents ductile features. Slight changes in hardness are also observed and maintained at about 60 HV. With increasing content of the RE element Y from 0.1 to 0.5%, the θ phase and Cu atoms in the matrix were reduced and most stopped at Grain boundaries (GBs). Micro-segregation and an enriched zone of Y near the GBs gradually increased. At the same time, the inter-metallic compound AlCuY is aggregated at grain junctions causing deterioration of the micro-structure and fracture properties of the alloy. After T6 treatment, the flatness of the fracture surface was lower than that of all the as-cast alloy showing lots of dimples and teared edges with a significant increase in hardness. When Y content was 0.1%, the strength and hardness of the alloy increased due to refinement of the grain strengthening effect. The content of Y elements segregated in the inter-dendritic zone and GBs is reduced. Plasticity and deformation compatibility also improved, making cracks difficult to form and merge with each other along adjacent grain junctions and providing an increased potential for ductile fracture. This paper proposes the addition of RE Y as an effective and prospective strategy to improve the fracture properties of the Al–Cu–Mn alloy and provide a meaningful reference in terms of improving overall performance.     

多向锻造及时效处理强韧化变形铝合金

利用多向锻造及时效处理技术加工变形铝合金,使铝合金具有高强度和良好的塑性.研究结果表明,试样组织显著细化且超细的第二相微粒弥散分布,抗拉强度和硬度大幅度增加且塑性良好,抗拉强度和延伸率分别为396.3 MPa和11.08％.锻件强度的大幅度提高,是由于组织显著细化且超细的第二相微粒弥散分布;经多次累积应变和时效处理改善晶界状态,同时,时效处理也减少锻造应力,使锻件的塑性增强.     

高温时效对25Cr35Ni-Nb合金碳化物的影响

25Cr35Ni-Nb合金被广泛用作乙烯裂解炉和制氢转化炉炉管材料,服役温度高达1050℃。将25Cr35Ni-Nb合金炉管在不同温度时效100 h,通过对不同温度显微组织的观察和维氏硬度测试,研究了不同温度时效后碳化物的变化规律。研究结果表明：随着时效温度的升高,晶界碳化物宽度不断增大,由原始铸态平均宽度1.5μm,增大到1200℃时效后的5.3μm;从900℃到1100℃,奥氏体晶内碳化物平均尺寸由1μm长大至2μm,然而,随着时效温度提高至1200℃,晶内碳化物平均尺寸下降至1.7μm。当时效温度从900℃增加为1100℃时,维氏硬度从173 HV10升高为192 HV10,1200℃时,维氏硬度为193 HV10。碳化物尺寸及维氏硬度与时效温度之间定量关系对炉管服役温度范围的确定提供了参考。     

Influence of T4 Heat Treatment on Tribological Behavior of Za27 Alloy Under Lubricated Sliding Condition

The effects of heat treatment on the microstructure, hardness, tensile properties, and tribological behavior of ZA27 alloy were examined. The alloys were prepared by conventional melting and casting route. The heat treatment of samples included the heating up to 370 °C for 3 or 5 h, quenching in water, and natural aging. Lubricated sliding wear test were conducted on as-cast and heat-treated ZA27 samples using block-on-disc machine. The friction and wear behavior of alloys were tested in contact with steel discs using combinations of three levels of load (10, 30, and 50 N) and three levels of linear sliding speeds (0.26, 0.50, and 1.00 m/s). To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, under all combinations of sliding speeds and contact loads. The rate of improvement increased with duration of solutionizing process before quenching in water. Obtained tribological results were related to the effects of heat treatment on microstructure changes of alloy.     

硼含量对铅镁铝合金组织与力学性能的影响

采用真空熔炼法制备了含硼的铅镁铝合金,通过扫描电子显微镜、X射线衍射仪、能谱仪和力学性能试验机等研究了硼含量对合金组织与力学性能的影响。结果表明:添加硼后,合金中出现了黑色的颗粒状AlB2相,且与Mg-Mg17Al12共晶组织相伴生;随着硼含量的增加,AlB2相分布趋于均匀化,Mg-Mg17Al12共晶相增多;当硼的质量分数为1%时,合金的力学性能最好,抗拉强度、硬度和伸长率分别为105MPa,160MPa和6.87%,室温拉伸断口主要为韧性断裂和准解理断裂的混合特征。