Stadler Manfred, Schnitzer Ronald, Gruber Martin, Steineder Katharina, Hofer Christina
Department of Materials Science, Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben, Austria.
Voestalpine Stahl GmbH, Voestalpine-Strasse 3, 4020 Linz, Austria.
Materials (Basel). 2021 Jun 17;14(12):3362. doi: 10.3390/ma14123362.
The properties of the heat-affected zone (HAZ) are reported to have a great influence on the mechanical performance of resistance spot welded advanced high strength steels. Therefore, in the present work, the HAZ of a medium-Mn steel is characterized regarding its microstructure and its mechanical properties depending on the distance to the fusion zone (FZ). In order to obtain the local mechanical properties of the HAZ, samples were heat-treated in a joule-heating thermal simulator using different peak temperatures to physically simulate the microstructure of the HAZ. By comparing the microstructure and the hardness of these heat-treated samples and the HAZ, the local peak temperatures within the HAZ could be determined. Subsequently, tensile tests were conducted, and the austenite phase fraction was measured magnetically on the physically simulated HAZ samples in order to determine the local mechanical properties of the HAZ. As verified by energy-dispersive X-ray spectroscopy, peak temperatures above 1200 °C led to a uniform distribution of manganese, resulting in a predominantly martensitic microstructure with high strength and low total elongation after quenching. Below 1100 °C, the diffusion of manganese is restricted, and considerable fractions of austenite remain stable. The austenite fraction increases almost linearly with decreasing peak temperature, which leads to an increase of the total elongation and to a slight decrease in the strength, depending on the distance to the FZ. Temperatures below 700 °C exhibit hardly any effect on the initial microstructure and mechanical properties.
据报道，热影响区（HAZ）的性能对电阻点焊先进高强度钢的力学性能有很大影响。因此，在本研究中，对一种中锰钢的热影响区进行了表征，研究了其微观结构及其力学性能与到熔合区（FZ）距离的关系。为了获得热影响区的局部力学性能，使用不同的峰值温度在焦耳热模拟装置中对样品进行热处理，以物理模拟热影响区的微观结构。通过比较这些热处理样品和热影响区的微观结构与硬度，可以确定热影响区内的局部峰值温度。随后，进行了拉伸试验，并对物理模拟热影响区样品进行了磁性奥氏体相分数测量，以确定热影响区的局部力学性能。能量色散X射线光谱分析证实，峰值温度高于1200℃会导致锰均匀分布，淬火后形成以马氏体为主的微观结构，具有高强度和低总伸长率。低于1100℃时，锰的扩散受到限制，相当一部分奥氏体保持稳定。奥氏体分数几乎随峰值温度降低呈线性增加，这导致总伸长率增加，强度略有下降，具体取决于到熔合区的距离。低于700℃的温度对初始微观结构和力学性能几乎没有影响。
