THERMAL DEMAGNETIZATION AND RANDOMNESS OF DOMAIN NUCLEATION OF SINGLE PHASE Nd_2 Fe_(14) B

Based on the observation of temperature variation of both domain structure and magnetic con-trast.the thermal demagnetization and randomness of domain nucleation was discussed.     

IN-SITU OBSERVATION OF CRACK TIP DEFORMATION IN A DUPLEX STAINLESS STEEL

The development of dislocation structures in the plastic zone ahead of a crack tip has been in-vestigated in a duplex stainless steel during in-situ deformation experiments in a scanningtransmission electron microscope.It was found that the dislocation distribution wassignificantly different in the ferrite and in the austenite.In the ferrite grains,the dislocationsemitted by the crack tip may cross-slip out of the original slip planes and form a broad plasticzone.However,in the austenite,the dislocation free zone is small and the dislocations emittedby the crack pile up in its slip plane.The selection of slip systems at the crack tip depends onthe crack tip Schmid factors in both phases.But after large deformation,the selection of thesecond slip systems at the craek tip in austenite does not depend on the Schmid factors.     

高强度钢腐蚀疲劳裂纹扩展的温度效应和过载迟滞效应

通过在18,35和55℃蒸馏水中疲劳裂纹扩展试验,证明了超高强度钢30CrMnSiNi2A腐蚀疲劳具有强烈的温度效应,得到了ΔK值和温度对裂纹扩展速率影响的复合表达式。由于扩展速率数据拟合得到的表观激活能值(36.7kJ/mol)十分接近于氢在γ-Fe中的扩散激活能值,支持了氢助裂纹扩展的观点。对大气中疲劳裂纹扩展具有重要价值的过载迟滞效应,在腐蚀疲劳时显著地减小,在0.1Hz的低频率下尤其明显。     

SIMULATION OF HEAT TRANSFER BY WATER SPRAY COOLING DURING CONTINUOUS CASTING OF LOW CARBON STEEL

本文研究了喷雾水滴与高温物体表面之间的传热。试验测定了锥形喷嘴的冷态特性和水滴与高温表面的传热系数,讨论了影响传热系数因素,并得出了h∝W关系式。     

THE BEHAVIOUR OF CARBON IN A Ni-BASE SUPERALLOY GH99 AND ITS INFLUENCE ON STRESS-RUPTURE PROPERTIES

在GH_99镍基合金中,无论加入多少碳,固溶在基体中碳的数量均相等(约为0.019wt-%),其余的碳则形成一次碳化物.合金在持久试验过程中,沿着与外力垂直的一次碳化物相界面产生裂口.出现这种裂口的一次碳化物的临界直径为0.80±0.05μm.合金中碳含量愈高,等于和大于这个临界尺寸的一次碳化物的数量就愈多,持久寿命降低的程度也就愈严重.合金的碳含量不超过0.05wt-%时,可显著地减少达到临界尺寸的一次碳化物数量.此外,与外力平行的晶界(纵向晶界)上的M_23C_6碳化物,朝着与外力垂直的晶界(横向晶界)上迁移,致使横向晶界上的M_23C_6数量增多且趋向连成一片.这必然弱化了晶界,损害持久性能.     

AN INVESTIGATION OF QUASI-CLEAVAGE FRACTURE IN STEEL

本文试图探讨准解理断裂的本质。联系多晶材料的典型应力一应变曲线,对不同钢的断裂韧度试样的断口分析表明,准解理断裂可以看作是一种过渡的断裂机制。首先,一系列微观解理裂纹在高拉伸应力集中地方生核,然后这些裂纹各自沿着它本身已变形晶粒的解理面上扩展,最后借助于微观塑性聚合方式,这些微裂纹彼此连接。根据上述断裂模型可以认为:解理裂纹与塑性变形间的相互作用是准解理断裂的一种重要性质。借助于断口定量分析方法,有可能把断口形貌和一些力学参数间关系建立起来。     

MAGNETIC PROPERTY AND THERMOSTABILITY OF Fe-BASE AMORPHOUS ALLOYS WITH HIGH SATURATION MAGNETIZATION

非晶态Fe_80B_(20),Fe_(17.84)B_(16.81)Si_(3.49)C_(1.36),Fe_(65.66)Co_(17.3)B_(15.84)Si_(1.2)和Fe_(6(?).92)Co_(17)B_(19.29)Si_(1.59)C_((?).(?))P_((?).(?))合金用单辊急冷法制备.测量了饱和磁化强度与温度的关系.得到0K时的原子磁矩(?)都在2.03—2.07μ_B之间.非晶态Fe_(80)B_(20)和Fe_(77.84)B_(16.81)Si_(3.49)C_((?).(?))合金的室温饱和磁化强度σ_s(R.T.)和Curie温度Tc相近,而含Co样品的σ_s(R.T.)和T_c分别高于Fe_(80)B_(20)约6%和13%.由热磁、电阻率、差热分析和X射线衍射的测量结果分析了样品的晶化转变.含Co样品的晶化温度T_(cr)与Fe_(80)B_(20)相近,而Fe_(77.84)B_(16.81)Si_(3.49)C_(1.86)的T_(cr)高于Fe_(80)B_(20)约80K.用化学键、T_(cr)与e/α的关系以及晶化过程的复杂性讨论了影响高饱和非晶态合金稳定性的因素.     

HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS

The oxidation rate,the growth,morphology and structure of oxide scale and whiskers forFe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied.The growth rate of scale is controlled by diffusion.The scale is composed of Cr_2O_3 andspinel(Fe,Mn)O·Cr_2O_3 and the oxide whisker,are spinel(Fe,Mn)O·Cr_2O_3.     

PREFERENTIAL SITE SATURATION FOR NUCLEATION AND GROWTH OF α-PHASE AT EARLY STAGE OF AUSTENITE DECOMPOSITION IN LOW CARBON STEEL BEARING BORON

借助经典体视学方法和“扩展组织”概念,定量研究了低碳硼钢620℃过冷奥氏体等温分解早期显微组织的演变路径。结果表明,母相晶界网络仍是低碳硼钢中α相形核长大的择优位置集合,择优顺序为晶粒棱(含隅)、晶界界面.棱集和隅集的位置饱和总是早于面集。钢中有效硼量对趋于饱和的路径和晶界面集的饱和迟早有显著影响。     

Nd_2(Fe_(0.9)Si_(0.1))_(14)B的中子衍射研究SCIEI

本文用中子衍射对Nd_2(Fe_(0.9)Si_(0.1))_(14)B在室温及77K进行了测量,用衍射峰的形状分析法进行了数据拟合。结果表明,在室温,Si择优占据4c,8j_1及16k_2晶位;Nd与Fe的磁矩平行于C轴排列。在77K,Si仍择优占据上述三个晶位。算得的Nd磁矩的方向偏离C轴37.8°。