Flow stress behavior of Al-Cu-Li-Zr alloy containing Sc during hot compression deformation

The flow stress behavior of Al-3.5Cu-1.5Li-0.25（Sc＋Zr） alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermal-mechanical simulator. Compression tests were preformed in the temperature range of 653-773 K and in the strain rate range of 0.001-10 s^-1 up to a true plastic strain of 0.7. The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature,and decreases with increasing temperature at a given imposed strain rate. The relationship between the flow stress and the strain rate and the temperature was derived by analyzing the experimental data. The flow stress is in a hyperbolic sine relationship with the strain rate,and in an Arrhenius relationship with the temperature,which imply that the process of plastic deformation at an elevated temperature for this material is thermally activated. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of n,α and A in the analytical expressions of flow stress σ are fitted to be 5.62,0.019 MPa^-1 and 1.51×10^16 s^-1,respectively. The hot deformation activation energy is 240.85 kJ/mol.     

Hot-compression behavior of Al-1Mn-1Mg alloy

The hot-compression of Al-1Mn-1Mg (mass fraction, %) alloy sample was carried out on a Gleeble-1500 thermo-simulator at deformation temperatures from 320 to 400 ℃ and strain rates from 0.1 to 10 s-1 by total strain of 1.4. Microstructure and texture evolution of the hot-compressed alloy were investigated by optical microscopy and X-ray diffraction analysis, respectively. The results show that the relationship among flow stress σ, deformation temperature T and strain rate ε can be expressed in the form of βσ...     

含微量Sc和Zr的Al—Cu—Mg—Fe—Ni合金时效行为和拉伸性能

配制了３种不同成分的Ａｌ－Ｃｕ－Ｍｇ－Ｆｅ－Ｎｉ系实验合金,研究了微量Ｓｃ和Ｚｒ对该系合金时效行为和拉伸性能的影响。用硬度法测量了合金在２００℃和３００℃下的时效硬化曲线,用航向电镜观察了合金在淬火及２００℃时效不同时间后的显微组织。在室温（２０℃）,２００,２５０,３００℃征测量了合金的拉伸力学性能,用扫描电镜观察了拉伸断口形貌。结果表明：加入微量Ｓｃ,Ｚｒ后生成的Ａｌ３（Ｓｃ,Ｚｒ）质点均匀弥     

热变形参数对Ti-15-3合金流动应力的影响

在Ｇｌｅｅｂｌｅ－１５００热模拟机上对Ｔｉ－１５－３合金试样进行了热压缩试验,以获得不同应变、应变速率和温度下材料的流动应力。根据相应的应力曲线研究了该合金在高温时的流动特性,并采用神经网络的方法建立了该合金高温变形抗力与应变、应变速率和温度对应关系的预测模型。结果表明,神经网络能够较精确地预测材料的流动应力。     

Hot compressive deformation behavior and constitutive relationship of Al-Zn-Mg-Zr alloy with trace amounts of Sc

Abstract： The hot deformation behaviors of AI-Zn-Mg-Sc-Zr alloy were investigated in a temperature range of 340-500℃ and a strain rate range of 0.001-10 s 1 using uniaxial compression test on Gleeble-1500 thermal simulation machine. The results show that the flow stress increases with increasing strain and tends to be constant after a peak value. The flow stress increases with increasing strain rate and decreases with increasing deformation temperature. The phenomenon of dynamic recovery and dynamic recrystallization can be observed by microstructural evolutions. Based on the hyperbolic Arrhenius-type equation, the true stress-true strain data from the tests were employed to establish the constitutive equation considering the effect of the true strain on material constants （α, β, Q, n and A）, which reveals the dependence of the flow stress on strain, strain rate and deformation temperature. The predicted stress-strain curves are in good agreement with experimental results, which confirms that the developed constitutive equations are suitable to research the hot deformation behaviors of Al-Zn-Mg-Sc-Zr alloy.     

Ageing behavior of an Al-Zn-Mg-Cu alloy pre-stretched thick plate

The ageing behavior of a pre-stretched thick plate of Al-Zn-Mg-Cu alloy was systemically studied including one-step ageing, two-step ageing, and retrogression and reageing treatment (RRA). One-step ageing of the alloy resulted in peak ultimate tensile strengths of 595 and 575 MPa after 22 and 6 h at 120 and 135°C, respectively. The strengthening phase in peak aged (T6 temper) alloy contained GP zones and the η′ phase predominantly. After two-step ageing, the electrical conductivity was increased markedly, but the pre-stretched thick plate sacrificed a great loss of strength. RRA treatment provided a method for maintaining the strength close to that obtained by T6 temper and for obtaining the high electrical conductivity close to that obtained by T7 temper; the ultimate tensile strength and electrical conductivity were 583 MPa and 21.0 MS/m, respectively. TEM analysis of T7 and RRA specimens revealed two types of precipitates that contributed to age strengthening i.e. the η′ and η phases.     

热压缩铝合金LY12流变应力的影响因素分析

采用Ｇｌｅｅｂｌｅ－１５００热力模拟机高温等温压缩实验,研究了铝合金ＬＹ１２高温塑性变形时的流变应力行为,研究结果表明,应变速率和变形温度的变化明显影响合金稳态流变应力的大小,且变形温度、应变速率、变形程序对流变应力也有一定的影响。     

The compressive deformation behavior and deformation mechanism of Ti14 alloy in semi-solid state

The semi-solid deformation behavior of Ti14 was investigated using compression tests at deformation temperatures between 1 273 and 1 423 K with strain rate of 5×10-2s-1. Moreover, the fraction solid at different temperatures was also measured by image analysis. The results showed that the deformation temperature had strong effects on the flow stress, and the stress increased with the decrease of deformation temperature. The maximum stress depended greatly on the fraction solid, and a sharp decrease in stress occurred at a solid fraction between 0.94 and 0.98(temperature from 1 323 to 1 373 K). This decrease was related to the decrease in the amount of solid bridges between grains. Because of the partial solid/liquid segregation during deformation, the experimental strain rates were much lower than those calculated by the flow of liquid incorporating solid particles, which suggested that the main deformation mechanism between 1 323 and 1 373 K was still plastic deformation of solid particles.     

PMAl—Li合金高应变速率超塑变形过程中的孔洞行为

用扫描电子显微镜及拉伸试验研究了ＰＡＭＡｌ－Ｌｉ合金高应变速率超塑型变形过程中孔洞的形核，长大及其影响因素，结果表明，孔洞主要有三角晶界和晶界突起处形核，其篚由周围的塑性变形控制，随应变速率的提高，孔洞的形核率和篚速率增加随变形温度的升高，孔洞的长大速率增加，材料对孔洞容纳性提高。     

元素粉末Ti,Al热压致密化过程分析

采用热模拟手段研究了温度为８００℃时元素粉末Ｔｉ,Ａｌ在热压过程中的致密化行为,测定了元素粉末Ｔｉ,Ａｌ在热压中后期的各种力学曲线,并获得了此时材料的致密化方程及应力－应变速度方程,结果表明：热压初期,由于元素粉末Ｔｉ,Ａｌ反应后压坯强度很低,大量的致密化在加压后的短时间内完成。     

Al-Mg-Si合金热压缩变形的流变应力方程

为了给制定和优化热加工工艺参数提供理论依据,采用Gleeble-1500热模拟机研究了含锆Al-Mg-Si合金在变形温度为653~803 K、变形速率为0.01~10s^-1条件下的热压缩变形的流变应力行为,并通过回归法建立材料变形的流变应力数学模型.结果表明：该合金为正应变速率敏感材料,真应力-真应变曲线存在明显的稳态流变特征;流变应力随着变形速率的增加以及变形温度的降低而增加;在较低变形温度条件下,真应力〖CDF*3〗真应变曲线为动态回复曲线;在较高变形温度条件下真应力-真应变曲线为动态再结晶曲线.该合金流变应力σ可用包含Arrhenius项的Zener Hollomon参数的函数来描述,式中A、α和n的值分别为1.89×10¹⁰s^-1、0.024MPa^-1和7.46,热变形激活能Q为166.85kJ/mol.     

Constitutive behavior of Ni-Ti shape memory alloy under hot compression

Constitutive behavior of nickel-titanium shape memory alloy (Ni-Ti SMA) under hot deformation was investigated by means of the compression tests and the linear fitting method. Based on the true stress-strain curves of Ni-Ti SMA under compression at the strain rates of 0.001-1s -1 and at the temperatures ranging from 600 to 1 000℃, the constitutive equation of Ni-Ti SMA with respect to the Zener-Hollomon parameter was established according to the high stress level and the low stress level at various temperatures so as to more accurately describe the deformation behavior of Ni-Ti SMA during hot working. Dynamic recovery and dynamic recrystallization of Ni-Ti SMA occur under hot compression, which lays the theoretical foundation for understanding the constitutive behavior of Ni-Ti SMA.     

Hot deformation behavior of low carbon steel during compression at elevated temperature

Hot compression tests of low carbon steel were carried out on Gleeble-3500 system in the temperature range from 750 to 900 ℃ and in the strain rate range from 0.001 to 1.0 s-1, and the associated microstructural evolution was studied by observations with a metallographic microscope. The results show that the stress-strain curves exhibit a peak stress at critical strain, after which the fl ow stresses decrease monotonically until reaching high strains, showing a dynamic fl ow softening. The peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by the Zener-Hollomon parameter Z in the hyperbolic sine equation. The fl ow stress increases with increasing strain rate and decreasing deforming temperature. The fl ow stress can be described by constitutive equation in hyperbolic sine function and can also be described by a Zener–Hollomon parameter Z. With increasing deformation temperature and decreasing strain rate, the grain size as well as the volume fraction of the recrystallized grains increase. The safe region for hot working of the alloy has been determined according to the processing map and microstructure at the true strain of 0.5, which is the deformation temperature of 840-940 ℃ and the strain rate of 0.001-1.0 s-1.     

Deformation behavior and microstructure of an Al-Zn-Mg-Cu-Zr alloy during hot deformation

The hot deformation behavior and microstructures of Al-7055 commercial alloy were investigated by axisymmetric hot compression at temperatures ranging from 300°C to 450°C and strain rates from 10-2 to 10 s-1,respectively.Microstructures of deformed 7055 alloy were investigated by transmission electron microscopy (TEM).The dependence of peak stress on deformation temperature and strain rate can be expressed by the hyperbolic-sine type equation.The hot deformation activation energy of the alloy is 146 kJ/mol....     

Deformation Behavior of 6063 Aluminum Alloy During High-Speed Compression

The deformation behavior characteristics of 6063 aluminum alloy were studied experimentally by isothermal compression tests on a Gleeble- 1500 thermal-mechanical simulator. Cylindrical specimens of 14mm in height and 10mm in diameter were compressed dynamically at temperatures ranging from 473 to 723K and at higher strain rntes from 5 to 30s^-1. It is fouud that the flow curves not only depend on the strain rate and temperature but nlso on the dynamic recovery aud recrystallization behavior. The results show that the flow stress decreased with the increase of temperature, while increased with the increase of strain rate. The discontinuous dynamic recrystallization （DDRX） may take place at a high strain rate of 20s^-1 under the tested conditions. At 30s^-1 , the flow curve can exhibit,flow softening due to the effect of temperature rise that raised the temperature by aboat 32K in less than 0.05s.     

Flow stress behavior of Cu13Zn alloy deformed at elevated temperature

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AZ31B镁合金和6065铝合金动态压缩行为数值模拟

为了研究帽状试样AZ31B镁合金和6065铝合金在动态压缩变形过程中的温度、应力与应变演变规律,采用Johnson-Cook本构方程和累积塑性损伤方程进行了数值模拟,运用有限元软件ANSYS/LS-DYNA模拟了AZ31B镁合金和6065铝合金帽状试样的动态变形过程.结果表明,两种合金的裂纹萌生和扩展过程相似,局域化变形带内塑性应变由内向外对称分布.相比于AZ31B镁合金,6065铝合金的塑性应变影响区域更为狭小,其应变和应变率硬化效果更强.6065铝合金的变形温度能够达到其动态再结晶临界点,因而易于绝热剪切带的形成.