Effect of Si on austenite stabilization,martensite morphology,and magnetic properties in Fe-26%Ni-x%Si alloys

The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si （x=3.5, 5, and 6） alloys have been studied by means of transmission electron microscopy （TEM） and M？ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field, and isomer shift values have been determined by Mssbauer spectroscopy. The M？ssbauer study reveals that the hyperfine magnetic field, the isomer shift values and the volume fraction of martensite decrease with increasing Si content.

Interfacial structure and mechanical property of Al2O3 and Invar brazed joint

This paper introduces a brazing process between Al2O3 ceramic and Invar alloy.Al2O3 can be brazed with Invar effectively.The interfacial structure of Al2O3/Invar joint can be expressed as：Invar/Ag（s,s）＋Cu（s,s）＋Fe2Ti（zone Ⅰ）/Ag（s,s）＋Cu（s,s）＋Fe2Ti＋NiTi＋Cu3Ti（zone Ⅱ）/Ag（s,s）＋Cu（s,s）＋Cu2Ti＋Al（s,s）＋TiC＋TiO（zone Ⅲ）/Al2O3.The maximum shear strength of 139 MPa was measured for as-brazed Al2O3/Invar joint brazed at 850℃ for 25 min or 900℃ for 15 min.

Dissimilar Joining of AISI 304L/St37 Steels by TIG Welding Process

In present work the weldings of an austenitic stainless steel （AISI 304L） and a ferritic carbon steel （St37） were conducted by tungsten inert gas （TIG） welding process using four different austenitic filler metals, namely ER308L, ER309L, ER316L and ER310. Microstructure characteristics and mechanical properties of the weldments were studied using optical and scanning electron microscopy, ferrit-ometry, hardness, tensile and impact tests. The ferrite number （_N-~） of the weldments made by different electrodes varies between 0.5 and 9.5. It was found that the increase in amount of delta ferrite in the microstructure of the weld metals, causes the decrease of the impact toughness of the weldments. It seems that using ER309L and ER316L electrodes can provide a good combination between the mechanical and metallurgical properties of the joint in AISI 304L/St37 dissimilar welding.

Microstructure Evolution of a 10Cr Heat-Resistant Steel during High Temperature Creep

The microstructure evolution of a 10Cr ferritic/martensitic heat-resistant steel during creep at 600℃ was investigated in this work. Creep tests demonstrated that the 10Cr steel had higher creep strength than conventional ASME-P92 steel at 600℃. The rnicrostructure after creep was studied by transmission electron microscopy, scanning electron microscopy and electron probe microanalysis. It was revealed that the martensitic laths were coarsened with time and eventually developed into subgrains after 8354 h. Laves phase was observed to grow and cluster along the prior austenite grain boundaries during creep and caused the fluctuation of solution and precipitation strengthening effects, which was responsible for the two slope changes on the creep rupture strength vs rupture time curve. It was also revealed that the microstructure evolution could be accelerated by stress, which resulted in the lower hardness in the deformed part of the creep specimen, compared with the aging part.