Effect of boron addition on the microstructure and stress-rupture properties of directionally solidified superalloys

This study is focused on the effect of boron addition, in the range of 0.0007wt% to 0.03wt%, on the microstructure and stress-rupture properties of a directionally solidified superalloy. With increasing boron content in the as-cast alloys, there is an increase in the fraction of the γ′/γ eutectic and block borides precipitate around the γ′/γ eutectic. At a high boron content of 0.03wt%, there is precipitation of lamellar borides. Upon heat treatment, fine block borides tend to precipitate at grain boundaries with increasing boron content. Overall, the rupture life of the directionally solidified superalloy is significantly improved with the addition of nominal content of boron. However, the rupture life decreases when the boron content exceeds 0.03wt%.

Microstructure and stress rupture properties of polycrystal and directionally solidified castings of nickel-based superalloys

A new directionally solidified Ni-based superalloy DZ24, which is a modification of K24 alloy without rare and expensive elemental additions, such as Ta and Hf, was studied in this paper. The microstructure and stress rupture properties of conventionally cast and directionally solidified superalloys were comparatively analyzed. It is indicated that the microstructure of K24 alloy is composed of γ, γ＇, γ/γ＇ eutectics and MC carbides. Compared with the microstructure of K24 polycrystalline alloy, γ/γ＇ eutectic completely dissolves into the γ matrix, the fine and regular γ＇ phase reprecipitates, and MC carbides decompose to M6C/M23C6 carbides after heat treatment in DZ24 alloy. The rupture life of DZ24 alloy is two times longer than that of K24 alloy. The more homogeneous the size of γ＇ precipitate, the longer the rupture life. The coarsening and rafting behaviors of γ＇ precipitates are observed in DZ24 alloy after the stress-rupture test.

Surgical Technique and Efficacy Analysis of Extra-pseudocapsular Transnasal Transsphenoidal Surgery for Pituitary Microprolactinoma

Objective To elucidate the role of transsphenoidal surgery in the treatment of pituitary microprolactinoma.Methods The clinical data of 107 prolactinoma cases treated by extra-pseudocapsular transnasal transsphenoidal surgery(ETTS)for different indications in our department since 2011 was retrospectively analyzed.Results The most common indication was the ineffectiveness of oral medication(41.1%),followed by the personal willingness of the patient(35.5%),and 20.6%of the patients were young women with clear tumor boundaries.The pseudocapsule was not observed in 63 cases(58.9%),incomplete pseudocapsule was observed in 26 cases(24.3%),and complete pseudocapsule in 18 cases(16.8%).A total of 97 patients(90.7%)obtained 1-year post-operation remission.According to the relative location of the adenoma and pituitary gland on the MRI scan,46 patients were classified into a central type,59 a lateral type,and 2 a supra-pituitary type.Two patients developed hypogonadism,one patient developed hypocortisolism,and one patient developed post-operative hypothyroidism.Two patients were administrated with hormone replacement treatment,and the treatment was stopped within one week.There was no permanent hypopituitarism.Further investigation demonstrated that the adenoma types could affect the remission rates of hyperprolactinemia and gross total resection rate in microprolactinoma.Conclusion ETTS was an effective treatment for pituitary microprolactinomas.This could be the first choice for patients who presented enclosed adenoma on the MRI and were potentially curable in a preoperative evaluation.Maximal safe removal of the adenoma by ETTS with the aim to increase the sensitivity of the drugs was also recommended for patients with invasive dopamine agonist resistant prolactinomas and patients with difficulty in childbirth.

Extra-pseudocapsular Transnasal Transsphenoidal Resection of Pituitary Macroadenoma:Technique Note and Evaluation of Endocrine Function

Objective In this study,we investigated the surgical technique and endocrine assessment of pituitary function of patients with macroadenoma treated by extra-pseudocapsular transnasal transsphenoidal surgery(ETTS).Methods Clinical data of 144 patients with pituitary macroadenomas in the same surgical group at the Department of Neurosurgery,Tongji Hospital,Tongji Medical College,Huazhong University of Science and Technology were retrospectively analyzed from January 2019 to June 2021.Based on the results of the endocrinological evaluation and MRI examinations before and after surgery,the fluctuation of pituitary function and the extent of resection were analyzed.Multiple Logistic regression analysis was used to determine the predictors affecting postoperative tumor residual.Results Among the 144 patients with pituitary macroadenomas,72(50.0%)were female and 72(50.0%)were male,the median age was 50 years,26(18.1%)had invasiveness grade 0,46(31.9%)had grade I,57(39.6%)had grade II,and 15(10.4%)had grade III according to Lu’s classification method.Based on observation during surgery,37 cases(25.7%)had no pseudocapsule,54 cases(37.5%)had incomplete pseudocapsule,and 53 cases(36.8%)had intact pseudocapsule.In addition,91(63.2%)patients had total resection,39(27.1%)had subtotal resection,and 14(9.7%)had partial resection.As for anterior pituitary function,13 of 19 hypothyroid patients had recovery after surgery,with a remission rate of 68.4%.Eighteen of the 26 decreased cortisol patients got back to normal,with a remission rate of 69.2%.A total of 27 of 51 patients with hypogonadism improved,with a remission rate of 52.9%.Univariate and multivariate analyses indicated that gender,tumor size,and invasiveness were predictors of postoperative residual in patients(P<0.05).Conclusion The results showed that ETTS is an effective treatment modality for restoring the function of pituitary gland of the patients with macroadenomas.Tumor size and invasiveness are predictors of the extent of surgical resection and postoperative residual of macroadenomas.