轧制对Mg-3Cu-1Mn合金温度阻尼峰的影响(英文)

经过变形量4.7%的单道次室温轧制变形,Mg-3Cu-1Mn合金的一次温度—阻尼谱出现了3个明显的阻尼峰;在二次温度—阻尼谱中,3个阻尼峰均发生变化,特别是第3阻尼峰P3受到抑制,变得非常不明显。对各阻尼峰峰温处淬火样品进行金相、XRD、EBSD等实验,研究轧制对Mg-3Cu-1Mn合金温度—阻尼峰的影响。结果表明:在一次温度—阻尼谱中的P3峰处出现织构增强、孪晶急剧消失的现象;轧制变形后,3个温度—阻尼峰依次为位错阻尼峰、晶界阻尼峰和孪晶引发的再结晶阻尼峰;另外,随着拉伸孪晶的消失,室温轧制态Mg-3Cu-1Mn合金的应变阻尼性能大幅度恢复,高应变下接近均匀化退火态Mg-3Cu-1Mn的应变阻尼性能。这说明拉伸孪晶对Mg-3Cu-1Mn合金应变阻尼性能有不利的影响。     

变形参数对AZ31镁合金板材织构的影响

利用X射线衍射(XRD)方法测量了不同轧制状态,即不同变形温度和变形量条件下AZ31镁合金板材织构的变化特征。结果表明,经过轧制之后的AZ31镁合金板材形成强烈的基面织构;在250℃~400℃范围内,变形温度的升高、变形量的增大都会促进镁合金板材棱柱面、锥面等非基面滑移系的启动,从而影响各织构组分的锋锐程度和板材各向异性的强弱。随着变形温度的升高,镁合金板材的各向异性减弱;变形量的增大,镁合金板材的各向异性增强。     

快速凝固Ni48Mn33Ga19合金的加热相变组织和结构的研究

采用铜模吸铸式快速凝固法制备了非化学计量成分的Ni48Mn33Ga19合金,研究和比较了经常规冷却和吸铸式快速冷却工艺热处理后合金相变点以及组织和结构的变化规律。结果表明,加热相变过程均为两阶段相变过程;快速凝固工艺可使铸后热处理试样的相变温度接近室温;极高的冷却速率提高了组织均匀性;Ni48Mn33Ga19合金组织经热处理后由奥氏体转变成10层马氏体。     

定向凝固Ni_(47)Mn_(32)Ga_(21)多晶合金的结构、相变及磁特性

采用定向凝固方法制备了Ni47Mn32Ga21多晶合金,通过XRD谱和金相照片研究合金的结构,通过对合金磁化强度与温度关系、电阻与温度关系、磁化曲线和磁感生应变曲线的测量分析,研究了合金的相变、磁化特性及磁感生应变特性。结果表明:Ni47Mn32Ga21合金在室温(298K)时为四方结构马氏体相,晶格参数a=b=0.593 8 nm,c=0.553 1 nm。合金的马氏体相变起始温度Ms和终止温度Mf分别为309 K和295 K,逆马氏体相变起始温度As与终止温度Af分别为306 K和319 K,居里温度TC为365 K。室温无压力下,Ni47Mn32Ga21合金有较好的双向可恢复磁感生应变,其饱和磁感生应变值达到-700×10-6。     

形变细化晶粒和润滑轧制对Ni-9.3at.%W合金基带立方织构形成的影响

采用光学显微镜(OM)、X射线四环衍射(XRD)技术、电子背散射衍射(EBSD)技术分析研究了形变细化晶粒、润滑轧制对Ni-9.3at.%W(Ni9.3W)合金基带立方织构形成的影响。结果表明,采用形变细化晶粒的方法能有效提高Ni9.3W合金基带的立方织构含量,并且随着初始形变量的增加,晶粒细化程度越大,立方织构含量越高,采用优化的形变细化晶粒工艺使得Ni9.3W合金基带立方织构含量提高了9.8%。另外,增加形变细化晶粒后的轧制总变形量,立方织构含量进一步提升了24.7%,根据以上结果,确定了初始坯锭制备阶段的参数。在此基础上,研究了轧制变形的润滑与非润滑对立方织构形成的影响,相比非润滑轧制而言,采用润滑轧制,轧制织构中获得了较多的S取向与Copper取向,经再结晶退火后,润滑轧制基带的立方织构含量比非润滑轧制基带的立方织构含量高9.6%,达到了86.7%(<15°),而且孪晶界数量、小角度晶界含量均要优于非润滑轧制,说明润滑轧制对立方织构形成有着积极的影响。     

冷变形对FeMnSiCrNi合金形状恢复率和转变温度的影响

通过Fe16Mn6Si7Cr7Ni合金变形量的大小和形变的类型来研究马氏体的转变特征.形变类型及变形量为:冷轧13%～28%;拉伸4%～17%.并通过热膨胀法测量合金相转变起始温度和转变终了温度,合金的相组成和微观结构特征通过XRD、SEM获得.研究结果表明:冷变形过程均会导致合金的形状恢复率降低,导致应力诱发ε、α/马氏体的形成,并使热马氏体的帆低于室温.     

Deformation and texture of copper–manganese alloys

Manganese is the only element that can be dissolved in copper up to 12% without markedly changing the stacking fault energy (SFE). Hence, investigation of the deformation behaviour of Cu–Mn alloys may yield insight into the influence of alloying elements apart from the (usual) decrease in SFE. The development of the crystallographic texture is analysed in various Cu–Mn alloys that were deformed either in compression or by cold rolling. The texture development is simulated by means of a novel materials-dependent Taylor-deformation model. The spatial arrangement of the rolling texture orientations in the as-deformed microstructure is studied by an orientation-sensitive etching technique. Despite the constant SFE, with increasing Mn content the rolling textures change from the pure metal (copper) type towards the alloys (brass) type. This effect is attributed to the altered deformation behaviour as well as the increased tendency to form shear bands due to the large increase in strength of the Cu–Mn alloys.     

磁性形状记忆合金Ni54Mn21Ga24.75Sm0.25的马氏体相变研究

本文通过内耗和交流磁化率,研究了多晶合金Ni54Mn21Ga25的马氏体相变特征,分析了稀土元素Sm对合金中间马氏体相变影响。研究结果表明,添加Sm使合金Ni54Mn21Ga24的马氏体相变温度提高到室温以上,并且降低了合金的温度滞后,在低磁场下Sm对合金磁感生应变影响不大。     

Fabricating Ni–Mn–Ga microtubes by diffusion of Mn and Ga into Ni tubes

Tubes of the ferromagnetic shape-memory alloy Ni–Mn–Ga of composition near the Ni₂MnGa Heusler phase can be used, alone or combined in structures, in magnetic actuators or magnetic refrigerators. However, fabrication of Ni–Mn–Ga tubes with sub-millimeter diameter by classical cold or hot drawing methods is hampered by the brittleness of the alloy. Here, we demonstrate a new process, where Ni–Mn–Ga tubes are fabricated by interdiffusion of Mn and Ga into drawn, ductile Ni tubes with 500 and 760 μm inner and outer diameters. After interdiffusion and homogenization of Mn and Ga at 1000 °C for 24–36 h, Ni–Mn–Ga tubes with ∼300 and ∼900 μm inner and outer diameters were obtained with homogeneous radial composition distribution, independently of the diffusion sequences (i.e., Mn and Ga diffused sequentially or simultaneously). Longitudinal composition was uniform over lengths of ∼1 mm, but variable over longer length due to incomplete process control. For two of the three diffusion sequences, a sizeable (20–80 μm) region exhibiting Kirkendall pores formed at the outer surface of the tubes. Magnetization values as high as ∼60 emu/g were measured, which is comparable to the magnetization of the Ni₂MnGa Heusler phase. X-ray diffraction on the tube with the highest magnetization confirmed the room-temperature structure as cubic austenite.     

热等静压法制备高立方织构的镍基合金复合基带

采用热等静压(HIP)法制备芯层为Ni-12％W(Ni12W,摩尔分数)合金、外层为Ni-5％W(Ni5W,摩尔分数)合金的Ni5W/Ni12W/Ni5W 3层复合初始坯锭:采用压延辅助双轴织构技术(RABiTSTM)通过直接冷轧及再结晶退火获得Ni5W/Ni12W/NiSW复合基带;采用X射线四环衍射技术(XRD)及背散射电子衍射技术(EBSD)对复合基带表面冷轧及再结晶织构进行分析.结果表明:冷轧复合基带表面形成较强的铜型形变织构,再结晶退火后复合基带表面形成锐利的立方织构,其立方织构含量达到99.1％(≤10°),与商业用Ni5W合金基带水平相当.     

AgCu28合金的织构组织与力学性能

用X射线衍射法研究AgCu28合金的轧制变形织构组织和退火织构组织,对它们的延伸率和抗拉强度进行测试。结果表明,当AgCu28合金轧制变形量为95%时,Ag和Cu的主要变形织构是{110}112Brass织构;在H2气氛下经650℃,1.5h退火后,AgCu28的退火织构与变形织构相同;加工态AgCu28合金沿横向(TD)和轧制方向(RD)的抗拉强度分别为750和680MPa,退火态AgCu28合金沿TD和RD的抗拉强度分别是374和327MPa;退火态沿TD和RD的延伸率都约为12%。这表明在两元共晶合金中两相晶粒相互影响导致它们的变形织构与退火织构一致、晶粒显著细化、再结晶温度明显提高、抗拉强度显著提高并存在各向异性。     

热处理工艺对制备粘结Ni52Mn24.4Ga23.6磁体的影响

采用真空感应熔炼法制备了多晶Ni52Mn24．4Ga23．6合金,用粉末压缩压制的方法制作粘结Ni52Mn24．4Ga23．6磁体;通过显微组织观察和差热分析(DSC)的方法研究了不同的浇铸方式和退火工艺对多晶Ni52Mn24．4Ga23．6合金铸锭组织和性能的影响。结果表明,缓慢冷却的合金液能得到晶粒粗大的合金铸锭;两步退火工艺能使合金铸锭具有确定的马氏体转变点,并促进马氏体变体的形核和长大。     

Effect of stress-induced martensitic transformation on the crack tip stress-intensity factor in Ni–Mn–Ga shape memory alloy

The Ni–Mn–Ga shape memory ferromagnetic shape memory alloys (FSMAs) are prone to fracture during thermal cycling. The present research shows that the primary reason for the thermally induced fracture of Ni–Mn–Ga FSMAs is the increase in the crack tip stress-intensity factor (SIF) due to stress redistribution around the crack tip as a result of stress-induced martensitic (SIM) transformation. On lowering the temperature to M_s, the crack tip SIF of Ni–Mn–Ga FSMA increases significantly, being very different from that of Ni–Ti and Cu–Al–Ni SMAs. The sensitive temperature dependence of crack tip SIF in Ni–Mn–Ga is responsible for its brittleness under thermal cycling. The temperature dependence of crack tip SIF is strongly related to the yield stress, the temperature dependence of the critical stress for SIM transformation and the transformation interval. Temperature rate also plays an important role in the fatigue behavior of Ni–Mn–Ga FSMAs under thermal cycling.     

Ni_(54)Mn_(25)Ga_(15)Al_6高温形状记忆合金的微观组织和相变行为(英文)

研究Ni54Mn25Ga15Al6高温形状记忆合金的微观组织、马氏体相变特性、力学性能和形状记忆效应。通过与Ni54Mn25Ga21合金对比,分析添加第四组元Al对Ni-Mn-Ga合金性能的影响。结果表明:Ni54Mn25Ga15Al6合金为单一的四方结构非调制马氏体相并呈片状的马氏体孪晶板条形貌。该合金的马氏体相变开始温度超过190°C,具有发展成为高温形状记忆合金的潜力。在Ni-Mn-Ga合金中添加Al会降低马氏体相变温度,这主要归因于Al添加引入的晶格尺寸因素的改变。添加Al元素能有效提高合金的强度和塑性,但降低合金的形状记忆性能。     

涂层导体用Ni9W合金基带再结晶及强立方织构的形成研究

采用X射线四环衍射技术对比分析了通过冷轧和轧制中间热处理制备的2种Ni-9.3at%W(Ni9W)合金基带的轧制织构和再结晶织构,研究了不同Ni9W合金基带在热处理过程中轧制织构向再结晶织构的演变。其次,采用背散射电子衍射(EBSD)技术对以上2种Ni9W合金基带的微观组织和立方织构进行了表征。结果表明,与传统冷轧Ni9W合金基带的轧制织构相比,经轧制中间热处理后其轧制织构中S取向和Copper取向的含量增加、Brass取向的含量减少,使其轧制织构的类型介于Brass型轧制织构与Copper型轧制织构之间。2种Ni9W合金基带经低温回复后,其轧制织构含量均有一定的增加;另外,再结晶过程中轧制织构的含量均迅速降低,但立方取向的含量并没有明显增加,而是出现大量的随机取向,Ni9W的再结晶具有了连续再结晶的特征,这也是导致Ni9W合金基带较难形成立方织构的一个主要原因。虽然经过轧制中间热处理后Ni9W合金基带在初始再结晶完成后并没有形成一定强度的立方织构,但其立方取向的含量仍然能在进一步热处理过程中通过立方取向晶粒的长大而得到加强。最后,采用轧制中间热处理制备的Ni9W合金基带经两步高温热处理后其立方织构的含量达到84.5%(15°)。     

镁合金织构与各向异性

介绍了镁合金变形及退火织构的组分与特点,论述了在挤压、轧制、等径角挤压等塑性变形及退火过程中镁合金织构的演变规律及形成机理,分析了织构与镁合金力学性能的基本关系,探讨了合金元素、变形温度、应变速度、外加应力及晶粒度等基本因素对镁合金织构特征与各向异性的影响.结果表明:织构对镁合金力学性能的影响,其实质是通过改变各滑移系特别是{0001}[1120]基面滑移系的Schmid因子、产生织构强化或软化而实现的.     

Effect of high-temperature quenching on the magnetostructural transformations and the long-range atomic order of Ni–Mn–Sn and Ni–Mn–Sb metamagnetic shape memory alloys

The influence of high-temperature thermal treatments on the martensitic transformation and the magnetic properties of Ni–Mn–Sn and Ni–Mn–Sb metamagnetic shape memory alloys have been investigated by calorimetric and magnetic measurements. Contrary to Ni–Mn–Ga and Ni–Mn–In systems, the martensitic transformation and Curie temperatures of Ni–Mn–Sn and Ni–Mn–Sb alloys are found to be unaffected by the increasing quenching temperature. Neutron diffraction measurements confirm the null effect of quenching on the next-nearest-neighbors atomic order due to the negligible L2₁ atomic disorder achieved with high-temperature annealings. The analysis of long-range order also suggests that no L2₁–B2 ordering transition takes place in the studied alloys, thus indicating an unusually high stability of the L2₁ structure. The obtained results show that the magnetostructural properties of Ni–Mn–Sn and Ni–Mn–Sb alloys cannot be properly tuned by means of standard thermal treatments.     

Microstructure and temperature monitoring during the hot rolling of AZ31

This study details the microstructural evolution during hot rolling of AZ31 alloy sheet using a pilot-scale rolling mill. The aim is to understand the deformation mechanisms leading to grain refinement under industrial processing conditions and to design and optimize the hot rolling schedule for AZ31 in order to produce sheet with a fine and homogeneous microstructure. The study examined three different hot rolling temperatures, 350, 400, and 450°C, and two rolling speeds, 20 and 50 rpm. A total thickness reduction of 67% was obtained using multiple passes, with reductions of either 15% or 30% per pass. It was found that the microstructure of the AZ31 alloy was sensitive to the rolling temperature, the reduction (i.e., strain) per pass and the rolling speed (i.e., strain rate). The results show that the large cast grain structure is broken down by segmentation of the cast grain through localized deformation in twin bands, where dynamic recrystallization occurs in these bands as well as at the grain boundaries (necklacing).     

温轧对Ni9W合金基带织构形成的影响

采用X射线四环衍射及电子背散射衍射技术对Ni-9.3at%W(Ni9W)温轧基带表面进行轧制织构与再结晶织构分析,研究了Ni9W合金基带温轧织构的形成与转变。结果表明,轧制过程采用温轧的方法能有效提高Ni9W合金基带轧制织构中的S取向与C取向的含量,并且随着变形量的增加Ni9W合金基带的形变织构由黄铜型织构向黄铜型和铜型的混合型织构转变,这有利于再结晶之后形成较强的立方织构。     

低Ni型LNG钢的热变形行为及力学性能

通过单道次、双道次压缩试验,研究了低Ni型LNG钢的高温奥氏体动态再结晶及静态再结晶行为,并采用两阶段控制轧制及超快速冷却技术进行不同轧制工艺下的热轧试验,通过热模拟及热轧试验研究了低Ni型LNG钢的热变形行为及力学性能。结果表明,在高温(1000~1050 ℃)、低应变速率(0.1~0.5 s^-1)下奥氏体容易发生动态再结晶,确定了发生再结晶的临界条件,并建立了动态再结晶动力学模型。试验钢在较高温度(800~1050 ℃)、较长道次间隔时间(60 s)下静态软化现象明显,容易发生静态再结晶。依据热模拟试验结果制定热轧试验工艺,通过控制精轧开轧温度和终轧温度调控高温奥氏体再结晶行为,从而细化晶粒,改善低Ni钢的冲击性能。精轧开轧温度920 ℃、终轧温度770 ℃时,低Ni钢的低温冲击吸收能量为180.1 J,屈服强度为595.1 MPa,抗拉强度为717.8 MPa。